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  • In situ measurement and experimental analysis of lithium mass transport in graphite electrodes
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Baoqin Shi, Yilan Kang, Haimei Xie, Haibin Song, Qian Zhang

    Herein, we measured the spatial distribution of the Li concentration and its mass transport processes in a porous graphite electrode in-situ. Insertion of Li into graphite changes the color of graphite by altering the visible light absorption; hence, we designed an optical electrochemical analog half-cell to enable direct real-time observations of the color change occurring during lithiation and delithiation. Using the relationship between the electrode color and Li concentration, we determined the distribution of the Li concentration in the electrode during intercalation. Our experimental results show that the distribution of the Li concentration was approximatively linear at the early stage of intercalation. As the Li content in the electrode increased, the distribution of the concentration became nonlinear and exhibited a ladder-like distribution owing to the effects of phase transformations. In addition, the time evolution of the Li concentration distribution curves was unsteady. On the basis of the distribution of the experimental concentration curves at different lithiation times, we determined the normalized overall lithium content within the electrode and its derivative over time (i.e., the Li mass transport rate). These results show that the overall lithium content increased nonlinearly over time. The Li transport rate decreased as the lithium content increased and fluctuated during phase transformation. On the basis of our experimental results, the effects of the Li concentration and the structural phase transformation on the Li transport rate are discussed.

    更新日期:2018-07-19
  • Amino acid-assisted synthesis of Fe2O3/nitrogen doped graphene hydrogels as high performance electrode material
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Dongling Wu, Penggao Liu, Tao Wang, Xingxing Chen, Liu Yang, Dianzeng Jia

    Fe2O3/nitrogen-doped graphene hydrogels are synthesized by a simple hydrothermal method using amino acids with different acidities as morphology-assisting and nitrogen-doping agents, simultaneously. The Fe2O3 show a mulberry-shape in the Fe2O3/NG-Aspartic composite, which presents a three-dimensional, loose porous network with a large specific surface area. The electrostatic and metal coordination-chelation interaction among the amino acid with different net charge, Fe3+ and graphene oxide affect the morphology, structure and final electrochemical properties of the Fe2O3/NG composites. The Fe2O3/NG-Aspartic shows a higher specific capacity, longer cycle stability and better rate capability, in comparison with the Fe2O3/NG samples prepared by using basic, neutral and non-nitrogen-doped composites. The Fe2O3/NG-Asp electrode provides high energy and power densities. The superior electrochemical performance of the Fe2O3/NG-Aspartic composite is ascribed to the battery-type capacity of iron oxide, the active sites introduced by the nitrogen-doping and the excellent proton-transfer due to the three-dimensional porous network structure of the graphene.

    更新日期:2018-07-19
  • The reduction of 4-nitrobenzene diazonium electrografted layer: An electrochemical study coupled to in situ sum-frequency generation spectroscopy
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    William Richard, David Evrard, Bertrand Busson, Christophe Humbert, Laetitia Dalstein, Abderrahmane Tadjeddine, Pierre Gros

    This work describes an electrochemical study of 4-nitrobenzene diazonium (4-NBD) reduction onto glassy carbon (GC) electrode coupled to in situ sum-frequency generation (SFG) spectroscopy. After 4-NBD grafting at 0.3 V vs. saturated calomel electrode (SCE) onto GC, SFG allowed a clear signal assigned to the symmetrical vibration mode of the nitro (NO2) groups to be observed at 1349 cm−1 or 1353 cm−1 depending on whether the spectrum was recorded in air or inside the solution. This result proved that 4-NBD grafting actually occurs at a potential as high as 0.3 V vs. SCE. The combination of SFG data and cyclic voltammetry (CV) also indicated that at such a potential, NO2 groups did not experience reduction process into hydroxylamine (NHOH) or amine (NH2) groups. The electrolysis of grafted NO2 moieties at −0.1 V was followed by CV and in situ by SFG. The exponential decay of the NO2 signal located at 1353 cm−1 vs. electrolysis time was in accordance with a charge transfer-limited reaction rate for a species immobilized at the electrode surface, and allowed a first order kinetic rate constant for NO2 reduction to be estimated k = 0.006 s−1. The integration of the peaks observed on the corresponding cyclic voltammograms (CVs) which were attributed to the NO/NHOH reversible system showed that the NO2 reduction produced both hydroxylamine and amine groups and was not quantitative. The fact that SFG spectroscopy was silent for long electrolysis time values suggested the remaining nitro groups to be located far from the electrode surface, as a consequence of an electron tunneling efficiency which decreased throughout the film thickness. Further electrolysis at −0.8 V allowed the remaining nitro groups to be reduced into NH2 with almost quantitative yields. All these results suggest the existence of a stratified layer during the electrolysis process, in which there is no limitation due to H+ diffusion in the organic film.

    更新日期:2018-07-19
  • Single frequency impedance strategy employed in rapid detection of leukemia cancer cells using an electrospun PES-nanofiber reinforced ternary composite-based cytosensor
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Mojtaba Shamsipur, Mohammad Bagher Gholivand, Hosna Ehzari, Afshin Pashabadi, Elham Arkan, Kamran Mansouri

    Cancer is one of the main causes of death in today's world, therefore, extending fast and reliable approaches for early monitoring of cancer cells have become one of the great challenges for scientists. This work reports exploiting a fast single frequency impedance strategy coupled to a new constructed composite for the quantitative detection of the human chronic myelogenous leukemia (CML) cell lines, K562. The platform used for the fabrication of the cytosensor is based on an electrospun poly[ethersulfone] (PES) sub-layer ready for improving by the upper nanodimension layers comprised of gold nanoparticles and multiwall carbon nanotubes (AuNPs/MWCNTs). The binding of K562 cancer cells with the pre-immobilized capture ssDNA was successfully transduced by Faradaic impedance spectroscopy (FIS). To diminish the possible nonspecific impedance changes that may cause some uncertainties in FIS signal, and to considerably decrease the time of the extended method, a fast single frequency measurement (SFM) strategy was tested based on recording total impedance |Z| in different individual frequencies, the methodology that was succeeded to recognize the target cells in measurement times as low as several seconds. Under the optimum conditions, the assessed signals were proportional to the population of K562 cells from 102 to 107 cells mL−1 with a calculated detection limit of 60 cells mL−1. The proposed biosensing-device also demonstrated high stability and reproducibility, which was able to offer great promise for the quantitative assay of K562 in routine analyses. The results of real sample analyses introduced the proposed device as alternative tool for CML K562 cell detection in real biological samples.

    更新日期:2018-07-19
  • Effects of different anionic dopants on the charge storage properties of binder less polypyrrole/vertically aligned carbon nanotube composites
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    M. Saghafi, M. Mahmoodian, S.A. Hosseini, A. Abdollahi, S. Mohajerzadeh

    In this paper, a polypyrrole/vertically aligned carbon nanotube (PPy/VACNT) composite has been prepared by in situ chemical polymerization of pyrrole precursor on the surface of VACNT electrode. VACNTs has been prepared by plasma enhanced chemical vapor deposition (DC-PECVD) from a mixture of H2 and C2H2 and were used as 3D nanoporous substrates. Effects of different dopant anions on the charge storage properties of PPy have been studied in this work. Camphor sulfonic acid, α-naphthalene sulfonic acid, anthraquinone-2-sulfonic acid sodium salt monohydrate/5-sulfosalicylic acid dehydrate, Sodium dodecylbenzenesulfonate and sodium dodecyl sulfate were used as anionic dopants. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction were used to characterize the electrodes. Cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy technique in 1 M HCl electrolyte were applied to investigate the electrochemical properties of electrodes. The results showed the specific capacity of electrodes was found to be in the order of the mentioned dopants at 10 mV s−1 scan rate. A maximum specific capacity of 332 C g−1 was obtained with PPy/VACNT which was doped with camphor sulfonic acid at 10 mV s−1 scan rate. In addition, the specific capacity of this electrode increased during cycling in 1 M HCl electrolyte which shows excellent cyclic life. The results show PPy-CSA/VACNT composite electrode have excellent characters of an electrode as a consequence of porous network structure and high electrochemical conduction which provides straight and fast ion transport pathways.

    更新日期:2018-07-19
  • Adaptive extended Kalman filter based state of charge determination for lithium-ion batteries
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Yanqing Shen

    The accurate online estimation of cell state of charge in electric vehicles is challenging due to extensive computational requirement, measurement noise and convergence issues. This paper proposes an adaptive extended Kalman filter based state of charge determination method, which employs improved simulated annealing method to access the uncertain states and adaptive switch mechanism to adjust the estimation algorithm. It combines the advantages of the local linear approximation and noise reduction capability from extended Kalman filter with the global optimization from improved simulated annealing. The method is verified by the samples collected from battery test system. Results illustrate that the proposed method estimates the cell remained capacity with great performance despite a range of common errors from initialization, current disturbance and measurement noise.

    更新日期:2018-07-19
  • Controlled synthesis of Na0.44MnO2 cathode material for sodium ion batteries with superior performance through urea-based solution combustion synthesis
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Nan Sheng, Cheng-gong Han, Yanhua Lei, Chunyu Zhu

    As a promising cathode material in sodium-ion batteries (SIBs) for large-scale energy storage applications, tunnel-structured Na0.44MnO2 is prepared by a facile and controllable urea-based solution combustion synthesis (SCS) method with subsequent calcination. The phase purity, morphology, homogeneity and particle size of the samples are quite dependent on the SCS fuel condition. The optimal sample f0.75 displays pure phase composition, high crystallinity and hierarchical-structured particles with uniform size of several microns, which are the agglomerates of well-calcined nano-rods and nano-slabs. The sample exhibits the highest reversible capacity of around 117 mAh/g at 0.1 C, good rate capability and excellent cycling stability, which even presents a high capacity of 100 mAh/g at 4 C after 300 cycles. The facile and controllable production and the superior electrochemical performance of the Na0.44MnO2 makes it a promising cathode material for the development of practical SIBs.

    更新日期:2018-07-19
  • Enhanced electrochemical performance of carbon and aluminum oxide co-coated Na3V2(PO4)2F3 cathode material for sodium ion batteries
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Di Ma, Lu-Lu Zhang, Tao Li, Chang Liu, Gan Liang, Ying-Xian Zhou, Xue-Lin Yang

    Carbon and aluminum oxide co-coated Na3V2(PO4)2F3 cathode material has been successfully prepared via a wet chemistry method. The effects of the hybrid layer coating of C and Al2O3 on crystalline structure, morphology and electrochemical performance have been investigated. It is found that C and Al2O3 co-coating can stabilize the structure and improve the conductivity of NVPF. As a cathode material for sodium-ion batteries, the co-coated NVPF electrode shows a significant enhancement in rate capability and cycling performance, i.e., compared with bare NVPF, C-coated NVPF and Al2O3-coated NVPF, the NVPF/C-Al electrode delivers the highest capacity of 122.8 mAh g−1 with a superior capacity retention ratio of 95.6% after 100 cycles at 1 C. This enhancement in cycling performance and rate capability can be ascribed to the protective effect of this hybrid coating layer of C and Al2O3 on NVPF from electrolyte attack and the facilitated electron/ion transmission caused by the hybrid coating layer. This modification method of co-coating with electronic conductor C and sodium ionic conductivity Al2O3 provides an effective way to improve the electrochemical properties of NVPF and other cathode materials with low electron/ion conductivity for sodium/lithium ion batteries.

    更新日期:2018-07-19
  • Morphology-dependent electrochemical performance of spinel-cobalt oxide nanomaterials towards lithium-ion batteries
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    T. Kesavan, S. Boopathi, M. Kundu, G. Maduraiveeran, M. Sasidharan

    Meticulous design and morphological tuning at nano/micrometer have been the focal point to modulate and comprehensively understand the kinetics of electrochemical reactions, especially in lithium-ion batteries (LIBs). In this report, we demonstrate an elegant approach to fabricate spinel-cobalt oxide (Co3O4) with sheet, pellet, flower, and cube-like morphologies. When evaluated as anode materials in LIBs, the Co3O4 nanomaterials with 2D sheet-morphology demonstrates the best electrochemical performance compared to those of Co3O4 materials with pellets-, flowers- and cube-like morphologies. Galvanostatic charge/discharge study of Co3O4 nanomaterials with 2D sheet-morphology shows an initial discharge capacity of 1618.0 mAh g−1 and a discharge capacity of 587.0 mAh g−1 is achieved even after 60 cycles at 0.1 C rate with an impressive columbic efficiency of ∼99%. Importantly, the sheet-structured Co3O4 electrode delivers a discharge capacity of 444.0 mAh g−1 at a high current of 1.0 C and provides 275.0 mAh g−1 even after 400 cycles with ∼99.0% columbic efficiency suggesting high electrode stability. The enhanced electrochemical performance of Co3O4 nanomaterials with 2D sheet-morphology is attributed to improved electrode/electrode interface with nano-sized particles and better accommodation of strain during charge/discharge processes compared to other morphologies.

    更新日期:2018-07-18
  • Electrochemical performance of polyaniline-derivated nitrogen-doped carbon nanowires
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Zhichao Zhao, Yibing Xie, Lu Lu

    The binder-free all-carbonaceous-component electrode was constructed by directly growing electroactive materials of nitrogen-doped carbon (NDC) on the substrate material of carbon paper (CP). The nitrogen-enriched polyaniline could be converted into NDC nanowires to cover on the surface of CP through electro-polymerization and carbonization processes. The polyaniline-derivated NDC electroactive material exhibits high capacity of 404.0 F g−1 at 1.0 A g−1. The superior capacitance results from the good electron-donor properties of heterocyclic nitrogen distributed in the carbon skeleton and reversible redox reactivity of exocyclic nitrogen-containing functional groups at the edge of carbon skeleton. A low capacity decay of 22% indicates high rate capability when current density increases from 1.0 to 10 A g−1. A high capacity retention ratio of 95.8% after 5000 cycles at 10.0 A g−1 presents good cycling stability. A symmetrical solid-state supercapacitor was constructed using NDC/CP electrode and polyvinyl alcohol-H2SO4 gel electrolyte. The device delivers a specific capacitance of 187.1 F g−1 at 1.0 A g−1, an energy density of 66.54 Wh kg−1 at the power density of 0.8 kW kg−1, the capacity retention ratio of 94.1% after 5000 cycles at 5.0 A g−1 and an output voltage of 1.6 V, which is comparable to the reported state-of-the-art carbon-based supercapacitor. The all-carbonaceous-component electrode presents promising application in electrochemical energy storage devices.

    更新日期:2018-07-18
  • Electrostatic self-assembly of LiFePO4 cathodes on a three-dimensional substrate for lithium ion batteries
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Guiying Tian, Frieder Scheiba, Lukas Pfaffmann, Andy Fiedler, Venkata Sai Kiran Chakravadhanula, Geethu Balachandran, Zijian Zhao, Helmut Ehrenberg

    In this work, the electrostatic self-assembly of LiFePO4 particles coated with polyelectrolytes on a three-dimensional carbon substrate is described. This new fabrication method allows precise control of ionic and electronic conduction pathways as well as the interfaces between the different electrode components, thus enabling new strategies for tailored electrode designs. Further, it is shown that the polyelectrolytes used to build up the electrode by electrostatic self-assembly can be converted into a conductive matrix by a simple carbonization step. This leads to a firmly adhering carbon film on the surface of LiFePO4, which further improves electron transport. The three-dimensional composite cathode exhibits a high specific capacity even at high current rates as well as a long cycle life. The excellent electrochemical performance can be attributed to the improved three-dimensional structure of the electrode as well as to the obtained intrinsic carbon coating of LiFePO4 particles.

    更新日期:2018-07-18
  • Metallic Sb nanoparticles embedded in carbon nanosheets as anode material for lithium ion batteries with superior rate capability and long cycling stability
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Xiaohui Zhang, Feiyan Lai, Zhenming Chen, Xingcun He, Qingyu Li, Hongqiang Wang

    Metallic antimony with high capacity, abundant and a very appropriate reaction potential is considered as a promising anode material for LIBs. But poor cycle performance due to the huge volume expansion during cycling process seriously hinders its practical application. Here, Sb nanoparticles encapsulated into carbon nanosheets were prepared by a facile and scalable method. And the carbon nanosheets can effectively buffer the volume expansion and inhibit the aggregation of Sb nanoparticles during the lithiation/delithiation process. Finally, the as-prepared Sb@C nanosheets display superior rate capability (418 mAh g−1 can be observed even at 5.0 A g−1) and long cycle stability (449 mAh g−1 can be maintained after 1000 cycle at 2.0 A g−1). Furthermore, when coupled with LiFePO4/C cathode, the Sb@C//LiFePO4/C full cell also exhibits outstanding electrochemical performance.

    更新日期:2018-07-18
  • Preparation of the poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate)@g-C3N4 composite by a simple direct mixing method for supercapacitor
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-18
    Yingxi Xu, Yafang Zhou, Jianyu Guo, Siyong Zhang, Yan Lu

    A promising electrode material for energy storage, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)@graphite-phase C3N4 composite is reported, which is prepared by a simple direct mixing process. The contents of g-C3N4 in the composite are investigated and optimized to give the best supercapacitor characteristics. The composite shows a good specific capacitance of 277 F g−1 at the current density of 1 A g−1 in 1 M H2SO4. More significantly, the composite exhibits the energy density of 10.2 Wh kg−1 at a power density of 4245 W kg−1. After 5000 charge/discharge cycles, the capacitance retention rate still remains at 94.2%.

    更新日期:2018-07-18
  • Probing the interactions in composite of graphene oxide and polyazulene in ionic liquid by in situ spectroelectrochemistry
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Milla Suominen, Pia Damlin, Carita Kvarnström

    Polyazulene (PAz) and polyazulene/graphene oxide composite (PAz/GO) films were electrochemically deposited from a choline based ionic liquid (IL), and characterized with attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) using Kretschmann geometry, and UV–Vis spectroscopy during electropolymerization and electrochemical oxidation. The use of different ILs has been shown to affect the morphology and long term cycling stability of PAz while fabricating composites is known to sometimes dramatically affect the electronic properties of PAz. The aim of this work was to study how the use of a viscous IL and, furthermore, incorporating GO affected the structural, electronic and optical properties of PAz. Overall, the vibrational behavior of the composite was very similar to PAz. During positive doping, the doping-induced infrared active vibrations (IRAV) of the composite were found at higher wavenumbers indicating shorter conjugation of PAz in the composite. Comparison to previous works and to PAz electropolymerized from conventional organic electrolyte solution revealed that polymerization in the viscous IL leads to electroactive and stable PAz with shorter effective conjugation length. The correlation between IRAV bands of doped PAz and Raman bands of neutral materials are also discussed within the framework of effective conjugation coordinate model (ECC).

    更新日期:2018-07-18
  • Highly efficient AuNi-Cu2O electrocatalysts for the oxygen reduction and evolution reactions: Important role of interaction between Au and Ni engineered by leaching of Cu2O
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Hongyu Gong, Shan Lu, Peter Strasser, Ruizhi Yang

    Electrochemical oxygen reduction reaction (ORR) during discharge and oxygen evolution reaction (OER) during charge are the key electrode processes for rechargeable metal–air batteries. In this article, we report a high-performance self-supported AuNi-Cu2O hybrid, which works as a bi-functional electrocatalyst for ORR and OER. The as-prepared AuNi-Cu2O hybrid exhibits excellent catalytic activity, the ORR activity of which is superior to that of commercial Pt/C, and the OER activity of which is close to that of commercial IrO2/C. Moreover, AuNi-Cu2O hybrid exhibits better durability than commercial Pt/C and IrO2/C. The excellent catalytic performance of AuNi-Cu2O could be attributed to the increase of active sites and the strong “mutual” interaction between Au and Ni induced by leaching of Cu2O.

    更新日期:2018-07-18
  • Porous magnetic iron- manganese oxide nanocubes derived from metal organic framework deposited on reduced graphene oxide nanoflake as a bi-functional electrocatalyst for hydrogen evolution and oxygen reduction reaction
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Behzad Rezaei, Ahmad Reza Taghipour Jahromi, Ali Asghar Ensafi

    In this work, the porous spinel-type of magnetic iron-manganese oxide nanocubes with a hollow structure deposited on the reduced graphene oxide nanoflakes (PMFMO@RGONF nanocomposite) is synthesized and examined as a non-noble electrocatalyst for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The Tafel slope of PMFMO@RGONF nanocomposite is about 107 mV dec−1 in the 0.50 mol L−1 H2SO4 solution and suggests the Volmer–Heyrovsky mechanism for HER. The results show that this electrocatalyst has an excellent stability (at least 10000 cycles) in the sulfuric acid solution. Hence, The LSV curve shows that the Pt(20%)/C has a better onset-potential than present electrocatalyst for HER but PMFMO@RGONF nanocomposite produces current density (j) of 300 mA cm−2 at overpotential (ɳ) of −721 mV (ɳ300 = −721 mV(vs. Ag/AgCl)) which is smaller than Pt(20%)/C (ɳ300 = −802 mV). The PMFMO@RGONF nanocomposite as an electrocatalyst follows four electrons mechanism for ORR in 0.10 mol L−1 KOH. As an important result, after addition of methanol into the electrolyte, this electrocatalyst is stable for a long time (at least 10000s) while the catalytic activity of Pt (20%)/C is quickly lost in the presence of methanol.

    更新日期:2018-07-18
  • Stabilization of cryptomelane α-MnO2 nanowires tunnels widths for enhanced electrochemical energy storage
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Aravindha Raja Selvaraj, Rajmohan Rajendiran, Deviprasath Chinnadurai, Gunasekaran Rajendra Kumar, Hee-Je Kim, Karuppanan Senthil, Kandasamy Prabakar

    One dimensional manganese oxides with tunnel structures have attracted as an effective electrochemical energy storage material because of its efficient electrolyte/cation interfacial charge transports which enables improved pseudo capacitive performance. We have reported a simple one step hydrothermal technique to incorporate K+ ions to maintain the tunnel width of cryptomelane α-MnO2 nanowires during cycling performance. The effects of K+ ions on the electrochemical performance is studied by tuning the phases of α-KMnO2 nanowires to Mn3O4 through an intermediate phase of Mn2O3 by subsequent calcinations at various temperatures. K+ ions doped α-MnO2 nanowires exhibit a highest specific capacitance of 402 Fg-1 at a current density of 1 Ag-1 in 1 M Na2SO4 electrolyte solution compared to Mn2O3 and Mn3O4. The as synthesized α-KMnO2 nanowires have a wider tunnel widths and enriched OH radical species and hence the electrolyte cations (Na+) penetrate the tunnels very easily resulting the polarization enhanced intercalation pseudo capacitance. The symmetric α-KMnO2 nanowire supercapacitor device shows very high energy density (15.83 Wh kg−1), power density (128.35 W kg−1) and excellent cyclic stability with 88% retention of the initial capacitance after 3000 cycles.

    更新日期:2018-07-18
  • Promising pyridinium ylide based anchors towards high-efficiency dyes for dye-sensitized solar cells applications: Insights from theoretical investigations
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Teng-Fei Lu, Wei Li, Jie Chen, Jianfeng Tang, Fu-Quan Bai, Hong-Xing Zhang

    We theoretically examine a series of anchors for dye-sensitized solar cells application, with particular attention was paid to the potential of novel pyridinium ylide based anchors. The geometrical structure, electronic property, and optical spectrum of the isolated dyes and its interface with TiO2 are analyzed by using quantum chemistry calculations. Quantum dynamics simulation is performed to investigate the interface electron transfer process across the dye/TiO2 interface. The key parameters influencing the short-circuit current and open-circuit voltage are calculated to quantify the performance of different dyes. Our results show that the pyridinium ylide based anchors benefit light-harvesting and improve intramolecular charge transfer character as well as shift up the conduction band edge of TiO2 semiconductor which further increase short-circuit current and open-circuit voltage. Conjugated rhodanime-3-acetic anchor exhibits the enhanced electron injection than the non-conjugated structure due to the more significant donor-acceptor interaction. The simulation performed in this work demonstrates the potential of novel pyridinium ylide based anchors with respect to the traditional carboxylic acid and rhodanime-3-acetic based anchors, reveals the crucial role of local structure variation in the interface electron transfer, and finally guides the design of high-efficiency sensitizer for dye-sensitized solar cells application.

    更新日期:2018-07-18
  • Enhanced electrochemical performance of perovskite LaNiO3 coating on Li1.2Mn0.54Ni0.13Co0.13O2 as cathode materials for Li-ion batteries
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Xiaodong Zhang, Junjie Hao, Licheng Wu, Zhimeng Guo, Zhenhui Ji, Ji Luo, Cunguang Chen, Jinfeng Shu, Haiming Long, Fang Yang, Alex A. Volinsky

    LaNiO3 thin film coated Li-rich cathode Li1.2Mn0.54Ni0.13Co0.13O2 material is fabricated for the first time using the facile sol-gel process. Morphology, structure and battery cycle performance of the LaNiO3-coated Li1.2Mn0.54Ni0.13Co0.13O2 is characterized by a series of tests. LaNiO3 coating was synthesized by the sol-gel process and uniformly covered powder surface. By coating proper amount of LaNiO3, the initial Coulombic efficiency, discharge capacity, rate capability and cycle performance are significantly improved, while the charge transfer resistance reduces. The initial Coulombic efficiency of 3 wt% LaNiO3-coating samples reaches the maximum of 70% and 65% at 0.1 C and 1 C rates, respectively. The 3 wt% LaNiO3-coating electrode has the highest initial charge/discharge capacity of 405.4/285.1 mAh g−1 at 0.1 C rate (1 C = 250 mA g−1), while 5 wt% LaNiO3-coating delivers the maximum value of 264.1/165.1 mAh g−1 at 1 C. The cycling performance profiles demonstrate that at 1 C rate, the 3 wt% LaNiO3-coated electrode exhibits higher discharge specific capacity of 207.6 mAh g−1 and cyclic stability of 190.3 mAh g−1 92% capacity retention after 50 cycles compared with pristine and other content LaNiO3. The film resistance and charge transfer resistance both decrease after coating with LaNiO3. LaNiO3 is an efficient modifier to enhance electrochemical performance of Li-rich cathode materials.

    更新日期:2018-07-18
  • A collaborative diagnosis on mesocarbon microbeads electrodes in dual-carbon cells with non-metal electrolytes
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Jiayu Li, Cheng Zheng, Li Qi, Hongyu Wang

    Dual-carbon cells are a promising candidate for new energy storage devices. Recently, a 4V asymmetric capacitor based on non-metal electrolytes has been proposed. Two kinds of mesocarbon microbeads(MCMB)samples with different treatments (potassium hydroxide activated MCMB and graphitized MCMB, labeled as AMCMB and GMCMB, respectively) have served as electrode materials in this study. The charge storage behaviors of MCMB electrodes are studied by in situ X-ray diffraction (XRD), in situ dilatometry and conventional electrochemical measurements. (−)AMCMB/GMCMB(+) is synergistically diagnosed as a superior electrode collocation from the viewpoint of structural changes, which consists of adequate activation (7.65% irrecoverable expansion) for AMCMB and suitable stretch (13.67% recoverable expansion) for GMCMB. The intercalation-induced activation of AMCMB is indiscernible in XRD patterns but becomes conspicuous as dilatometric responses. A quantitative correlation between the two in situ measurements is established in the research of GMCMB electrodes. Expansions in the two dimensions are closely related to the type and size of intercalated ions, the shrinkage behavior of electrodes is especially synchronous in the discharging process. These findings guide the design of advanced cells and emphasize the necessity combining in situ characterizations.

    更新日期:2018-07-18
  • Catalytic polymerization of N-methylthionine at electrochemically reduced graphene oxide electrodes
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Chuanxiang Chen, Zhengyang Gan, Kang Zhou, Zhen Ma, Yinqiu Liu, Yuhua Gao

    Electronic structures of conducting polymers could change in the presence of other conjugated materials. Poly(N-methylthionine) (PNMTh) has a lower conductivity and a slower polymerization rate at conventional electrodes as compared to polyaniline. Here, we present a novel enhanced electroactive and electrochromic PNMTh/electrochemically reduced graphene oxide (ERGO) composite by the combination of electrochemical reduction and catalytic polymerization: ERGO acts as both the efficient template and catalyst for the NMTh polymerization, and also offers both the high conductivity and large surface area to enhance the electrochemical and electrochromic behaviors of the pure PNMTh. The morphology and composition of the obtained composite was characterized via X-ray photoelectron spectra (XPS), UV–Visible (UV–Vis) spectra, Fourier transformed infrared (FTIR) spectra, and scanning electron microscopy (SEM). The obtained PNMTh/ERGO composite has a good potential to be used in (bio-) sensors, biofuel cells, electrochromic devices, and other electrochemical applications.

    更新日期:2018-07-18
  • Binder-free electro-synthesis of highly ordered nickel oxide nanoparticles and its electrochemical performance
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Thomas Nesakumar Jebakumar Immanuel Edison, Raji Atchudan, Yong Rok Lee

    In this work, highly ordered nickel oxide nanoparticles were electrochemically synthesized on nickel foam (NiOx NPs/Ni foam) via the formation and subsequent heat treatment of nickel hydroxide. The synthesized NiOx NPs were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) with elemental analysis and high resolution transmission electron microscopy (HR-TEM). The XRD results revealed the presence of two different oxide phases with high crystallinity. The synthesized NiOx NPs were highly ordered spherical morphology with average size of 7 nm, identified from the FE-SEM images. Further, the electrochemical performance of synthesized NiOx NPs/Ni foam was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge discharge (GCD) methods. The calculated specific capacity of NiOx NPs/Ni foam was found to be 219 C/g (60.7 mAh/g) at scan rate of 5 mV/s. This present work implies that the electro-synthesized NiOx NPs/Ni foam as a good binder-free, highly stable battery-type material and it can be used as a positive electrode for hybrid-capacitors.

    更新日期:2018-07-18
  • Embedded CuO nanoparticles@TiO2-nanotube arrays for photoelectrocatalytic reduction of CO2 to methanol
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Liqiang Zhang, Huazhen Cao, Qiuyuan Pen, Liankui Wu, Guangya Hou, Yiping Tang, Guoqu Zheng

    Herein, we report a simple approach to synthesize high-performance and structurally stable CuO nanoparticles catalyst embedded in TiO2 nanotube arrays for CO2 reduction. To summarize, anodic TiO2 nanotube arrays (TNTs) were electrochemical reductive doped in 1 mol/L (NH4)2SO4 solution to form an activated surface. Then CuO nanoparticles were successfully filled into the pores pace of TNTs by electrodeposition and heat treatment. The effects of Ti(Ⅲ) reduction doping were discussed by means of electrochemical impedance spectroscopy (EIS) and X ray photoelectron spectroscopy (XPS). Results show that partial Ti(Ⅳ) in TNTs can be reduced to Ti(Ⅲ) by electrochemical reduction, which leads to an significant improvement in TNTs surfactivity and then benefits the deposition of Cu nanoparticles to form a stable embedded structure. As a consequence, the composite electrodes showed higher photoelectrocatalytic performance for CO2 reduction. The maximum current of CuO-TNTs composite electrodes is up to −1.37 mA/cm2 at −0.5 V and high selectivity for methanol synthesis is also obtained in this case. At the same time, the amount of methanol produced by the CuO/self-doped TNTs composite electrode is about 15% higher than that by the CuO/TNTs electrode without reductive doping.

    更新日期:2018-07-18
  • TiO2 nanosheets anchoring on carbon nanotubes for fast sodium storage
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Yan Zhang, Wanwan Hong, Yu Zhang, Wei Xu, Zidan Shi, Xifei Li, Hongshuai Hou, Xiaobo Ji

    The ultrathin TiO2 nanosheets doped by nitrogen tightly attaching on carbon nanotubes are designed and evaluated as anode for sodium ion batteries. The TiO2 nanosheets attaching on carbon nanotubes composite shows a high specific capacity of 248.5 mAh g−1 at the rate of 0.5 C, and it can still deliver a specific capacity of 100.9 mAh g−1 at a high rate of 20 C, which verifies an outstanding sodium storage capacity and an excellent rate capability. More encouragingly, at a rate of 10 C, the specific capacity can be still kept at 154.2 mAh g−1 after 3500 cycles, displaying a remarkable long-term cyclic stability. Note that the corresponding kinetics analysis suggests that the pseudocapacitive behavior is responsible for the updating sodium storage performances of TiO2 nanosheets composite. Additionally, the cooperation effects of carbon nanotubes preservation and nitrogen modification can provide fast electronic pathways, and the TiO2 nanosheets can promote sodium ions transport and increase the active sites for sodium storage. The merits of multiple functional and tailor-designed strategies make contributions to develop high-performance TiO2 anodes in sodium ion batteries.

    更新日期:2018-07-18
  • Sandwich-like NiO/rGO nanoarchitectures for 4 V solid-state asymmetric-supercapacitors with high energy density
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Ao Liu, Haitao Zhang, Gao Wang, Jiahe Zhang, Suojiang Zhang

    Hierarchical NiO/reduced graphene oxide (rGO) nanohybrids with tunable microstructures were fabricated via the thermal decomposition of Ni(OH)2/rGO formed by the electrostatic attraction between exfoliated Ni(OH)2 and GO nanosheets. Characterization study revealed that the size of intercalated NiO nanocrystals could be tuned from 2 nm to 10 nm, and the specific surface area of optimized nanohybrids reached to 255 m2/g. Ionogel polymer electrolyte was prepared by entrapping ionic liquid (EMImBF4) and lithium salt (LiTFSI) into copolymer (PVdF-HFP). Effect of NiO particle size on the electrochemical performances was evaluated systemically. Asymmetric supercapacitors with as-prepared nanohybrids as anode and commercial activated carbon as cathodes were assembled. Aqueous 6 M KOH solution, organic LiPF6 solution and ionogel polymer were utilized as electrolytes to check their compatibility with nanohybrids. Our study shows that supercapacitors exhibit energy densities of 31.6 Wh/kg, 49 Wh/kg and 146 Wh/kg, respectively, with the above mentioned electrolytes. These results clearly demonstrate that high performance can be actualized by the subtle combination of hybridized electrodes with high voltage formulated ionogel polymer electrolytes.

    更新日期:2018-07-18
  • An integrated theoretical-experimental approach to understand facilitated proton transfer-electron transfer coupled reactions at thick-film modified electrodes
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Franco Martín Zanotto, Tamara Ayelén Hernández, Ricardo Ariel Fernández, Sergio Alberto Dassie

    The main purpose of the current work is to generalize the analytical model for the facilitated proton transfer-electron transfer coupled reactions at thick organic film-modified electrodes, including ion pairing in the organic phase and considering non-ideal electrolyte solutions in both phases. The main equations to calculate half-wave potentials developed in this model allow the simulation of different chemical systems, comprising hydrophilic and hydrophobic neutral weak bases, at different experimental conditions such as pH, organic phase to aqueous phase volume ratio, and concentration ratios between the redox probe and the transferring protonated species. The model was checked against experimental voltammetric responses measured with the transfer of Tylosin A at the water|1,2-dichloroethene interface. Consequently, we present here an integrated theoretical-experimental approach in order to compare the results of our previous model [Zanotto et al. Electrochim. Acta 258 (2017) 727–734] with experimental data from Tylosin A and predicted half-wave potentials.

    更新日期:2018-07-18
  • Cotton yarns modified with three-dimensional metallic Ni conductive network and pseudocapactive Co-Ni layered double hydroxide nanosheet array as electrode materials for flexible yarn supercapacitors
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Hai-Tao Wang, Chun Jin, Ya-Nan Liu, Xiao-Hui Kang, Shao-Wei Bian, Quan Zhu

    A novel cotton/Ni/Co-Ni layered double hydroxide (CT/Ni/Co-Ni LDH) hybrid yarn electrode material is prepared by constructing a three-dimensional (3D) metallic Ni conductive network on the cotton fiber surface for rapid electron transportation and subsequently in situ growing Co-Ni LDH nanosheet array layers with high electrochemically active surface area for faradic reactions. The 3D porous electrode structure facilitates the effective electrolyte ion diffusion. The obtained yarn electrode material shows a high areal capacitance of 1.26 F/cm2 (121571.1 C/cm2) at a scan rate of 5 mV/s, as well as a stable electrochemical performance under various mechanical deformations. An all-solid-state yarn supercapacitor device is further assembled based on the obtained yarn electrode materials, which exhibits a high energy density of 9.3 μWh/cm2 at a power density of 43.99 μW/cm2.

    更新日期:2018-07-18
  • Distinction in anodic dissolution behavior on different planes of laser solid formed Ti-6Al-4V alloy
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Jiaqiang Li, Xin Lin, Min Zheng, Jian Wang, Pengfei Guo, Tuo Qin, Minghui Zhu, Weidong Huang, Haiou Yang

    Microstructure, electrochemical impedance, and Tafel and potentiodynamic polarizations were characterized to investigate the electrochemical anodic dissolution behavior of Ti-6Al-4V alloy produced by the laser solid forming (LSF) additive manufacturing process with a specific focus on the distinction on different planes. Electrochemical measurements show that the anodic dissolution characteristic of LSFed Ti-6Al-4V reveals anisotropic behavior on different planes. The horizontal-plane (XOY plane) is more resistant to corrosion than the vertical-plane (XOZ plane) in 15 wt% NaCl solution. Additionally, the vertical-plane shows a lower initial machining potential for the process of electrochemical machining compared to the horizontal-plane. The microstructure of Ti-6Al-4V alloy deposit is composed of dominant α-laths and small amounts of β phase, and its horizontal-plane has higher content of the β phase, lower content of the α phase, slightly finer α-laths, and more uneven α-lath width distribution compared to the vertical-plane. These differences in the microstructural characteristics produce the distinctions observed in the electrochemical anodic dissolution behavior of LSFed Ti-6Al-4V alloy on the vertical- and horizontal-planes.

    更新日期:2018-07-18
  • Fabrication of Fe-doped Co2P nanoparticles as efficient electrocatalyst for electrochemical and photoelectrochemical water oxidation
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Guang Liu, Na Li, Yong Zhao, Rui Yao, Muheng Wang, Dongying He, Jinping Li

    Fe-doped Co2P nanoparticles (Fe-Co2P) are successfully synthesized using a facile and scalable solid reaction method and demonstrate highly efficient oxygen evolution reaction (OER) activity towards water splitting. Benefiting from the synergistic effect of Fe, Co and P as well as enlarged electrochemical active surface area (ECSA), the resultant Fe-Co2P nanoparticles yield extraordinary OER performance with an overpotential as low as 289 mV at 10 mA cm−2, a small Tafel slope of 40 mV dec−1, and excellent OER stability, which are superior to the individual Co2P, Fe2P as well as the commercial RuO2 electrocatalyst. Moreover, Fe-Co2P nanoparticles are also shown to be a resultful co-catalyst to promote the photoelectrochemical (PEC) water oxidation performance of α-Fe2O3 photoanode, leading to a cathodic potential shift of ∼200 mV at 1.0 mA cm−2 and a significantly promoted photocurrent density of 1.40 mA cm−2 at 1.23 VRHE with respect to that of bare α-Fe2O3. The effective synthesis method and electronic modulate-induced enhancement of OER by hetero-atom doping highlight the promising design and fabricate of various efficient bimetallic or polymetallic phosphides for photo-/electrochemical water splitting.

    更新日期:2018-07-18
  • Facile electrochemical synthesis of three dimensional flowerlike gold microstructure for electrochemical oxidation of hydrogen peroxide
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Alagan Muthurasu, Hak Yong Kim

    In the present work, we report a simple and facile templateless electrodeposition of hierarchical flowerlike gold microstructure which was synthesized by using an chronoamperometric (CA) i–t curve technique at a constant applied potential of E = 0.5 V with respect to sat Ag/AgCl (KCl) on indium tin oxide electrode (ITO) substrate. The surface morphology, elemental composition and the preferred orientation of gold microflowers (AuMFs) were characterized using scanning electron microscopy (SEM) and X–ray photoelectron spectroscopy (XPS) analyses. The SEM images of the as-prepared AuMFs resembled nanoflakes which are building block for the formation of a three dimensional hierarchical flower–like morphology. Surface elemental composition and valence state of AuMFs is further examined by X–ray photoelectron spectroscopy (XPS). The electrochemical oxidation behavior of AuMFs was investigated by using Cyclic Voltammetry (CV) and chronoamperometric CA techniques with the H2O2 analyst in 0.1 M phosphate buffer solution (pH 7.4). The AuMFs deposited ITO electrodes exhibited excellent electrocatalytic reactivity towards H2O2 oxidation due to the increase of in adsorption of H2O2 on gold–oxide surfaces and it was enhancing the amperometric sensing of H2O2 in neutral solutions.

    更新日期:2018-07-18
  • Polypyrrole thin film on electrochemically modified graphite surface for mechanically stable and high-performance supercapacitor electrodes
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    C. Justin Raj, Ramu Manikandan, Won-Gil Lee, Won-Je Cho, Kook Hyun Yu, Byung Chul Kim

    A few-layer graphene oxide-based supercapacitor electrode was fabricated via direct and controlled electrochemical exfoliation of graphite in 0.1 M H2SO4 electrolyte. The graphite electrode exfoliated for a 5 min reaction shows the presence of a few layers of graphene oxide on the surface and exhibited excellent electrochemical performance with maximum areal capacitance of 993 mF cm−2. However, the electrode failed to retain its surface state under continuous charge/discharge cycles due to the subsequent exfoliation of graphene layers from the graphite surface. But, the deposition of a thin polypyrrole layer effectively reinforces the surface states of the electrode with better mechanical stability as well as electrochemical performances. The fabricated graphite/graphene oxide/polypyrrole electrode showed an improved areal capacitance of 1320 mF cm−2. Moreover, the electrode exhibited ∼83% cyclic stability after 5000 charge/discharge cycles, which is higher than the stability of graphite/graphene oxide electrode (67%).

    更新日期:2018-07-18
  • Probing the nucleation, growth, and evolution of hydrogen nanobubbles at single catalytic sites
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Rukshan T. Perera, Christopher E. Arcadia, Jacob K. Rosenstein

    We present measurements of the nucleation, growth and evolution of single hydrogen nanobubbles containing zeptomoles of molecular hydrogen and likely originating from a single catalytic site. These bubbles are measured using nanoscale platinum and gold meniscus-contacted electrodes, whose picoliter volumes facilitate rapid supersaturation and evolution of bubbles. Observed periodic current transients were utilized to understand the nucleation, growth, coalescence, and evolution of single nanobubbles at different overpotentials and pHs. This provides a novel platform to understand factors governing bubble nucleation and evolution. These measurements offer exciting possibilities to connect experiments with computational models in important energy applications.

    更新日期:2018-07-18
  • Layer-by-layer assembly of iron oxide-decorated few-layer graphene/PANI:PSS composite films for high performance supercapacitors operating in neutral aqueous electrolytes
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Gonzalo E. Fenoy, Benoit Van der Schueren, Juliana Scotto, Fouzia Boulmedais, Marcelo R. Ceolín, Sylvie Bégin-Colin, Dominique Bégin, Waldemar A. Marmisollé, Omar Azzaroni

    The layer-by-layer assembly of polyaniline-PSS (PANI:PSS) complexes and iron oxide nanoparticles-decorated few-layer graphene (Fe-FLG) from aqueous dispersions, yielding an electrode material with excellent electrochemical capacitive performance in simple neutral aqueous electrolyte is presented. The simple dip-coating procedure allows the effective incorporation of both materials and the control of the film nanoarchitectonics. The resulting composite coating was characterized by XPS and Raman spectroscopies. A linear dependence of the capacitance on the film mass indicates that both building blocks are efficiently (and electrochemically) connected within the films. The electrochemical performance of the film-coated electrodes was tested in both acidic (0.1 M HCl) and neutral (0.1 M KCl) aqueous electrolytes. Electrodes constituted of 15 self-assembled bilayers showed the best performance with a high capacitance of 768.6 F g−1 and 659.2 F g−1 in 0.1 M HCl and 0.1 M KCl, respectively, at the current density of 1 A g−1. Moreover, a high stability to continuous cycling was observed, even in aqueous neutral solution (86% capacitance retention after 1600 cycles at 3 A g−1). This ternary material then constitutes a promising candidate for the construction of environmentally friendly supercapacitors.

    更新日期:2018-07-18
  • Superelastic active graphene aerogels dried in natural environment for sensitive supercapacitor-type stress sensor
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Ning Wei, Qiang Wang, Yue Ma, Limin Ruan, Wei Zeng, Dong Liang, Chao Xu, Linsheng Huang, Jinling Zhao

    A superelastic and active graphene aerogel with nitrogen and boron co-modification is developed by a simple naturally drying post-process. The resulting aerogel owns a robust three-dimensional architecture which exhibits highly repeatable compressibility even under 80% strain. In addition, the aerogel material offers a high specific capacitance of 336 F g−1 at 0.25 A g−1, the energy density of 13.99 Wh kg−1 at the power density of 47.25 W kg−1, and 90.74% specific capacitance retention even after 2000 cycles. Based on the symmetrical aerogel electrodes in a supercapacitor-type device structure, a facile novel self-powered stress sensor is developed. In the external stress load ranging from 0.05 to 10 N, the charged sensor demonstrates rapid current response, good linear relationship between log(I) and log(T), and outstanding cycle stability. The unique preparation and sensor application may lead to new exploitation for graphene aerogel in future electronic device.

    更新日期:2018-07-18
  • Nanostructured nitrogen doped diamond for the detection of toxic metal ions
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Sujit Deshmukh, Kamatchi Jothiramalingam Sankaran, Svetlana Korneychuk, Johan Verbeeck, James Mclaughlin, Ken Haenen, Susanta Sinha Roy

    This work demonstrates the applicability of one-dimensional nitrogen-doped diamond nanorods (N-DNRs) for the simultaneous electrochemical (EC) detection of Pb2+ and Cd2+ ions in an electrolyte solution. Well separated voltammetric peaks are observed for Pb2+ and Cd2+ ions using N-DNRs as a working electrode in square wave anodic stripping voltammetry measurements. Moreover, the cyclic voltammetry response of N-DNR electrodes towards the Fe(CN)6/4-/Fe(CN)6/3- redox reaction is better as compared to undoped DNR electrodes. This enhancement of EC performance in N-DNR electrodes is accounted by the increased amount of sp2 bonded nanographitic phases in N-DNR electrodes, enhancing the electrical conductivity at the grain boundary (GB) regions. These findings are supported by transmission electron microscopy and electron energy loss spectroscopy studies. Consequently, the GB defect induced N-DNRs exhibit better adsorption of metal ions, which makes such samples promising candidates for next generation EC sensing devices.

    更新日期:2018-07-18
  • The high Tafel slope and small potential dependence of activation energy for formic acid oxidation on a Pd electrode
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Nestor Uwitonze, Da Zhou, Jing Lei, Wei Chen, Xia Qing Zuo, Jun Cai, Yan-Xia Chen

    Formic acid oxidation (FAO) on Pd electrode at various temperatures is investigated by cyclic voltammetry, potential step chronoamperometry and electrochemical in situ infrared spectroscopy (IRS). With increasing potential, FAO activity first increases, then decreases at higher potentials, the peak potential increases from 0.65 V to ca. 0.9–1.0 V with increasing temperature from 298 K to 343 K. The Tafel slope for FAO on Pd is found to be ca.260 ± 40mV/dec at around 0.25 V, it increases with the electrode potential and reaches ca. 470 ± 20 mV/dec at around 0.5 V. The apparent activation energies (Ea,app) and pre-exponential factors (Aapp) are estimated from the cyclic voltammograms or current transients recorded at different temperatures. Ea,app decreases slightly with increasing reaction potential from 0.25 V to ca. 0.6 V with a slope of ca. 0.27 eV/V. The H/D kinetic isotope effect is found to be ca. 2 in the potential region from 0.2 V to 0.4 V, it increases with potential at E > 0.4 V and reaches ca. 6 at 0.6 V. Only bridge-bonded bicarbonate and formate are detected by IRS during FAO on Pd, the role of these species for FAO on Pd are discussed. Possible origins for the large Tafel slope, and the correlation between the large Tafel slope and the small potential-dependent change of the activation energy are discussed.

    更新日期:2018-07-18
  • The oxophilic and electronic effects on anchored platinum nanoparticles on sp2 carbon sites: The hydrogen evolution and oxidation reactions in alkaline medium
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    C.A. Campos-Roldán, R.G. González-Huerta, N. Alonso-Vante

    The impact of sp2 sites of amorphous carbon and carbon nanotubes toward the hydrogen evolution/oxidation reactions on Pt nanoparticles, in alkaline medium, is described. The kinetic enhancement is given through the induced UV-photons of selectively photo-deposited platinum nanoparticles (Pt NPs) onto sp2 domains. The, henceforth, induced sp2 strong metal support interaction favors the electronic, and the oxophilic effects boosting the kinetics of hydrogen reactions.

    更新日期:2018-07-18
  • Half-cell and full-cell applications of sodium ion batteries based on carbon-coated Na3Fe0.5V1.5(PO4)3 nanoparticles cathode
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Renming Zhan, Bolei Shen, Qiuju Xu, Youquan Zhang, Yushan Luo, Heng Liu, Hao Chen, Feng Liu, Changming Li, Maowen Xu

    Pristine Na3Fe0.5V1.5(PO4)3 and carbon-coated Na3Fe0.5V1.5(PO4)3 nano-particles are synthesized by one-step solid-phase reaction method. The full battery based on Na3Fe0.5V1.5(PO4)3@C nano-particles as cathode and commercial hard carbon as anode outputs a high working voltage about 3.3 V and exhibits superior-rate performance. While the rate increases from 0.5 to 1, 2 and 5 C, the discharge capacity of full battery slightly decreases from 110 to 94, 88, 79 mA h g−1 gradually. Moreover, it shows excellent cycle stability with a capacity retention of 93.8% after 200 cycles at 0.5 C.

    更新日期:2018-07-18
  • Novel nanostructured indium tin oxide electrode for electrochemical immunosensors: Suitability for the detection of TNF-α
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Raquel Pruna, Abdoullatif Baraket, Anne Bonhommé, Nadia Zine, Abdelhamid Errachid, Manel López

    The need for new and innovative point of care (POC) systems providing a feasible alternative to costly and time consuming standard laboratory techniques is becoming more evident every day, particularly in the case of cardiovascular diseases. Coupling optical and electrochemical principles for highly specific and sensitive detection of biomarkers could boost the successful implementation of POC systems in biomedical environments. We suggest indium tin oxide (ITO) as a promising material for working electrodes in optoelectrochemical sensors, owing to the rare combination of high electrical conductivity and optical transparency it presents. Moreover, the nanostructured nature of the electrodes' surface is crucial for an eventual miniaturization of the POC system. In this work, we describe the construction and characterization of a nanostructured ITO electrode modified with aryl diazonium salt as transparent substrate for electrochemical immunosensors. The developed electrode was tested for the detection of tumour necrosis factor α (TNF-α), a cardiac biomarker playing an important role in the prevention of heart failure. Macro and microscopic evidences (gathered from electrochemical and spectral techniques) of covalent bonding and high surface coverage are provided. Specific interaction between antigen (TNF-α) and monoclonal antibody (Ab-TNF-α) was verified by fluorescence patterning, confirming the proper bio-recognition of the cytokine. As a proof-of-concept, results of electrochemical impedance spectroscopy (EIS) show stabilized semi-quantitative label-free detection of TNF-α at several concentrations (from 10 pg/mL to 100 pg/mL). These preliminary results demonstrate the feasibility of using transparent substrates for the detection of cytokines at low concentrations, and the consequent application in POC systems for the monitoring of cardiovascular diseases.

    更新日期:2018-07-18
  • Electrochemical biosensing platform based on molecularly imprinted polymer reinforced by ZnO–graphene capped quantum dots for 6-mercaptopurine detection
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Behnaz Hatamluyi, Zarrin Es'haghi

    A new quantum dot consisting of a ZnO core wrapped in a shell of graphene (ZnO@GQD) was synthesized and applied for the construction of an innovative electrochemical sensor for sensitive and selective determination of 6-mercaptopurine (6-MP). The sensor was fabricated based on the pencil graphite electrode (PGE) coated with a sol-gel binder reinforced with polypyrrole (PPy) based molecularly imprinted polymer (MIP), and ZnO@GQD core-shell nanoparticles with a homogeneous environment. The procedure was carried out through a facile one-step electropolymerization stage. The synthesized quantum dots were studied by Fourier transform infrared (FT-IR) spectrometry, X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX). Electrochemical characterization of the sensor was performed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). To clarify the oxidation mechanism of 6-MP, various voltammetry techniques were used. Electrochemical measurements using differential pulse voltammetry (DPV) method showed a wide linear relationship between 6-MP concentration and peak height within the range 0.01–50.0 μM and 50.0–700.0 μM with a lower detection limit (5.72 nM). The imprinted sensor was highly sensitive and was successful to detect 6-MP in real spiked samples.

    更新日期:2018-07-18
  • Nitrogen doped carbon coating of PbLi2Ti6O14 as high electrochemical performance anode towards long-life lithium storage
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Haoxiang Yu, Yafen Zhang, Xing Cheng, Haojie Zhu, Runtian Zheng, Tingting Liu, Jundong Zhang, Miao Shui, Jie Shu

    To fulfill the requirement for large-scale energy-storage systems, lithium ions batteries have been attracted great attentions. It is necessary to develop the anode material with high rate capability, long cycling life and outstanding safety. Here, N-doped carbon been successfully synthesized and estimated as an anode material for lithium ions batteries. PbLi2Ti6O14 is isostructural with SrLi2Ti6O14. After nitrogen-doped carbon coating, PbLi2Ti6O14@NC delivers a high capacity of 143.2 mAh g−1 at a current density of 100 mA g−1 and remains 104.8 mAh g−1 even at 700 mA g−1. In addition, PbLi2Ti6O14@NC also possesses excellent cyclic stability. The reversible capacity of PbLi2Ti6O14@NC can keep at 99.7 mAh g−1 after 1500 cycles. Such results are also proved by CV tests and EIS measurements. Meanwhile, the lithium storage mechanism of PbLi2Ti6O14@NC is investigated by an in situ XRD technique. It indicates that PbLi2Ti6O14@NC has a stable structural host. These aforementioned results suggest that PbLi2Ti6O14@NC has great potential working as an anode material for lithium ions batteries.

    更新日期:2018-07-18
  • Metal-doped molybdenum nitride films for enhanced hydrogen evolution in near-neutral strongly buffered aerobic media
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Arun Prasad Murthy, Durai Govindarajan, Jayaraman Theerthagiri, Jagannathan Madhavan, Kuppusami Parasuraman

    A series of molybdenum nitride films, viz., Mo3N2, Ag-Mo3N2, V-Mo3N2 and Cu-Mo3N2 have been fabricated by magnetron co-sputtering technique and evaluated as HER electrocatalysts in near-neutral pH (pH 5) buffer medium. An optimal HER activity has been observed at about 1.8 M phosphate buffer with Cu-Mo3N2 showing highest activity. Under strongly buffered and oxygen saturated conditions the molybdenum nitride films have consistently shown very high HER selectivity in the presence of oxygen. The stability of the molybdenum nitride films has been enhanced retaining almost 100% of the initial activity in a durability test, whereas, a significant loss in the stability has been observed for the same catalysts in 0.5 M H2SO4 solution.

    更新日期:2018-07-18
  • Electrochemical properties of NASICON-structured glass-ceramics of the Li1+xCrx(GeyTi1-y)2-x(PO4)3 system
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-17
    Rafael B. Nuernberg, Ana C.M. Rodrigues, Michel Ribes, Annie Pradel

    The electrochemical stability window of NASICON-structured glass-ceramics of the Li1+xCrx(GeyTi1-y)2-x(PO4)3 system is investigated by a combination of cyclic voltammetry, electrochemical impedance, and X-ray photoelectron spectroscopy techniques. Cyclic voltammetry analyses are performed using a three-electrode setup cell where Ag3SI/Ag is applied as a reference electrode. Cyclic voltammetry measurements are followed by in situ electrochemical impedance spectroscopy, enabling the effect of oxidation and reduction reactions on the electrical properties of the glass-ceramics in question to be determined. X-ray photoelectron spectroscopy, in turn, is applied to determine which chemical species undergo reduction/oxidation. Our findings reveal that the electrochemical stability of this material is limited by the reduction of Ti+4 cations in low potentials (around 2.1 V vs. Li+/Li) and by the oxidation of O−2 anions in high potentials (4.8 V vs. Li+/Li). After the first cycle, the electrolytes seem to be stable within a much broader electrochemical window than in the first cycle. However, the results indicate not only that the reduction at low potential is not deleterious to the electrical properties of the electrolytes but also that the oxidation reaction at high potentials is highly detrimental. These findings contradict the common perception about the outstanding stability of NASICON-structured electrolytes in oxidation potentials.

    更新日期:2018-07-18
  • Carbonous metallic framework of multi-walled carbon Nanotubes/Bi2S3 nanorods as heterostructure composite films for efficient quasi-solid state DSSCs
    Electrochim. Acta (IF 5.116) Pub Date : 2018-04-21
    Anam Ali Memon, Supriya A. Patil, Kyung Chul Sun, Naveed Mengal, Alvira Ayoub Arbab, Iftikhar Ali Sahito, Sung Hoon Jeong, Hak Sung kim

    Bismuth sulfide (Bi2S3); is a non-toxic metal chalcogenide and a promising semiconductor in energy storage devices, but it has not received much attention in the regime of dye sensitized solar cells (DSSCs). The present research describes the synthesis of highly electro-catalytic active counter electrode (CE) material for quasi-solid state dye sensitized solar cells (QDSSCs), namely carbonous metallic heterostructure composite (CMHC), composed of solution processed bismuth sulfide nanorods and modified Multi walled carbon nanotubes (MWCNTs). Due to the positive synergistic effect of conductive MWCNT network and rod-like morphology of bismuth sulfide, the composite exhibits multifunctional characteristics of high conductivity, superior electro-catalytic activity and optimal porosity. The carbonous composite with a dominant oxygen rich surface shows enhanced electro-catalytic activity, low charge transfer resistance (RCT), and exceptional cyclic stability as compared with pristine bismuth sulfide. The as-synthesized composite exhibit a very low charge transfer resistance of 0.9 Ω which signifies a fast electron transport mechanism. The suggested composite CE with 3% polymer gel electrolyte achieves a high efficiency of 8.24% comparable to Pt (8.47%). Based on the facile synthesis of composites and excellent performance of CE, the designed quasi-solid state dye sensitized solar cells stand out as an efficient next generation solar cells.

    更新日期:2018-07-14
  • Thermodynamic stability mapping and electrochemical study of La1-xSrxCo0.2Fe0.8O3 ± δ (x=0.2–0.4) as a cathode of solid oxide fuel cells in the presence of SO2
    Electrochim. Acta (IF 5.116) Pub Date : 2018-04-27
    Shadi Darvish, Cheng Cheng Wang, San Ping Jiang, Yu Zhong

    Thermodynamic predictions and electrochemical analysis of secondary phase formation in SO2 containing atmosphere on the surface of La1-xSrxCo0.2Fe0.8O3±δ (x = 0.2–0.4) electrodes of solid oxide fuel cells have been carried out utilizing the CALculation of Phase Diagram (CALPHAD) approach. Impact of temperature, SO2 partial pressure, O2 partial pressure as well as the cathode composition on the formation of secondary phases have been investigated and correlated with the previous investigations in the literature. The results predict that SrSO4, CoFe2O4, La2O2SO4 and La2(SO4)3 has the possibility to form on the surface and at the cathode/electrolyte interface as a result of SO2 existence in the system. It is also investigated that degradation occurs more severe for La0.6Sr0.4Co0.2Fe0.8O3±δ (LSCF-6428) comparing to LSCF-7328 and LSCF-8228, due to the formation of higher amount of secondary phases, specifically SrSO4. The results demonstrate the effectiveness of the computational thermodynamic modeling in the prediction of interaction and performance stability of SOFC cathodes in the presence of contaminants.

    更新日期:2018-07-14
  • Hierarchical Cu doped SnSe nanoclusters as high-performance anode for sodium-ion batteries
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-10
    Rusong Chen, Shenzhou Li, Jianyun Liu, Yuyu Li, Feng Ma, Jiashun Liang, Xian Chen, Zhengpei Miao, Jiantao Han, Tanyuan Wang, Qing Li

    Tin selenide (SnSe) has been explored as a promising anode material for sodium ion batteries (SIBs) but its electrochemical performance is strictly limited by the large volume variation during charge/discharge process and relatively low electronic conductivity. In this work, hierarchical Cu doped SnSe nanoclusters were prepared by a cost-efficient and nontoxic method and demonstrated as a high-performance anode for SIB. Under optimized Cu doping degree (10 wt% Cu), the developed Cu-SnSe anode exhibits excellent rate performance with a high capacity of 330 mAh/g at 20 A/g and outstanding stability with a capacity of 304 mAh/g after 1000 cycles at 5 A/g (0.1–3.0 V vs. Na/Na+). The enhanced electronic conductivity, facilitated sodiation/desodiation process, and relieved volume change during cycling in Cu doped SnSe benefited from Cu doping and the unique hierarchical structure should account for its extraordinary SIB performance.

    更新日期:2018-07-12
  • Synthesis and conductivity behaviour of Mo-doped La2Ce2O7 proton conductors
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-10
    Taiping Tu, Bo Zhang, Jian Liu, Kewen Wu, Kaiping Peng

    Mo-doped La2Ce2O7 with varied concentrations are prepared by the traditional citrate-nitrate combustion method. The effects of the phase structure of Mo-doped La2Ce2O7 are investigated by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and conductivity measurements. X-ray diffraction patterns reveal that all La2-xMoxCe2O7+δ samples have a cubic structure. Neverly, hole can be found on the surface of the samples from scanning electron microscopy. Raman spectra show that the different vibrating structures of pellets can be changed by introducing Mo into La2Ce2O7. Detailed X-ray photoelectron spectroscopy studies on the oxidation states of La2Ce2O7 and La1.85Mo0.15Ce2O7+δ indicate ratios of OC to OT (OT = OC + OL) are between 32.21% and 46.24%. The conduction behavior of Mo doped La2Ce2O7 electrolyte is seriously researched under air and 5%H2-95%Ar conditions at 350–700 °C, and the highest conductivity of 7.36 × 10−3 and 1.65 × 10−2 Scm−1, respectively, are obtained with La1.85Mo0.15Ce2O7+δ pellets at 700 °C. The highest power density of single cells with the La1.85Mo0.15Ce2O7+δ electrolyte is approximately 0.643 Wcm−2 at 700 °C, suggesting that Mo-doped La2Ce2O7 can be used to substantially improve the electrochemical performance of low-temperature solid oxide fuel cells.

    更新日期:2018-07-12
  • Facile solid-state synthesis of eco-friendly sodium iron silicate with exceptional sodium storage behaviour
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-10
    Karthikeyan Kaliyappan, Zhongwei Chen

    It is crucial to develop stable energy sources for rechargeable sodium-ion batteries using simple synthesis methods. Herein, we report a facile route for synthesizing phase-pure carbon-coated Na2FeSiO4 polyanionic cathodes using conventional solid-state methods at 700 °C under inert atmosphere. X-ray diffraction results reveal that there are no impurities in the highly crystalline Na2FeSiO4 particles, resulting from the heat of combustion provided by the organic chelating agent. The electrochemical behaviour of Na2FeSiO4 particles is tested within 1.5–4.5 V at 0.25 C. The Na2FeSiO4 cathode delivered 119 mAh g−1 at 0.25 C and maintained ∼85% of its initial capacity after 200 cycles after activation process. Even at high current densities of 3.5 C, the material outperforms other orthosilicates-based cathodes reported with capacities of 55 mAh g−1 discharge capacity along with ∼80% retention after 1000 cycles. The enhanced performance of carbon-coated Na2FeSiO4 particles is ascribed to the improved electronic conductivity by the incorporation of carbon and the presence of void space between the particles. This void space contains more electrolytes and eliminates the stress formed during the cycling process, thus improving stability even at high rates. This is the first report on obtaining phase pure metal orthosilicate material with negligible impurities using simple solid-state method along with such exponential electrochemical performances.

    更新日期:2018-07-12
  • Two dimensional holey carbon nanosheets assisted by calcium acetate for high performance supercapacitor
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-10
    Chenglong Cai, Qingli Sui, Zhe She, Heinz-Bernhard Kraatz, Cuili Xiang, Pengru Huang, Hailiang Chu, Shujun Qiu, Fen Xu, Lixian Sun, Afzal Shah, Yongjin Zou

    Nanostructured carbon materials are the first preference for fabricating electrodes as they have intrinsic conductivity, excellent chemical stability and high surface area. In this report, a novel two dimensional (2D) holey carbon nanosheet was prepared by pyrolysis of a composite of resorcinol–formaldehyde resin (RF) and calcium acetate (CA), followed by acid etching and base activation. The results reveal that CA plays a crucial role in the formation of the 2D holey carbon nanosheet. The CaO originated from the decomposition of CA was found not only to act a template for the holes, but a catalyst for the graphitic carbon. The obtained carbon nanosheet exhibited uniformly distributed holes with an average diameter of 60 nm. The hierarchical micro/mesoporous structure has a high surface area of 1258.2 m2 g−1, which is great for the fabrication of electrode materials in supercapacitor. It delivered a specific capacitance of 360.1 F g−1 at the current density of 1.0 A g−1 in 6.0 M KOH solution. Furthermore, a two-electrode symmetric supercapacitor based on the carbon material displayed an energy density of 13.3 Wh kg−1 at a high power density of 7125 Wkg–1. The supercapacitor also showed superior rate capability, cycle stability and great potential for use in practical applications.

    更新日期:2018-07-12
  • A high-performance dual-ion cell utilizing Si nanosphere@graphene anode
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-10
    Shuai Wang, Xiang Xiao, Yanping Zhou, Chaopeng Fu, Shuqiang Jiao

    The growing global demands of high-safety, low-cost and high working voltage energy storage devices trigger great interests in novel batteries beyond state-of-the-art lithium-ion battery. Herein, we firstly fabricate a novel rechargeable dual-ion cell with graphite cathode and Si nanosphere@graphene (Si-NS@G) composite anode in a LiPF6-based organic electrolyte. The graphene layers anchored onto Si nanospheres surface can accommodate the volume expansion and improve the electrical conductivity of Si nanospheres. The cell shows stable long-term cycling and excellent rate performance with a high discharge capacity of 100 mA h g−1 at the current density of 100 mA g−1 after 1000 cycles. Moreover, the cell operates a high working voltage of >4.2 V, enabling a higher energy density. Our result may open a new paradigm for novel electrochemical cell technologies and applications.

    更新日期:2018-07-12
  • Nickel-manganese structured and multiphase composites as electrodes for hybrid supercapacitors
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-10
    L. Soserov, A. Stoyanova, T. Boyadzhieva, V. Koleva, M. Kalapsazova, R. Stoyanova

    Hybrid supercapacitors with the composite electrode materials display high energy density at the expense of the reduced cycle stability. Herein, we provide new data on the electrochemical performance of hybrid electrodes based on mixed nickel hydroxides/manganese oxides in the form of structured and multiphase composites. As structured composites, two types of less known structure modifications are examined: interstratified modification of Ni(OH)2 (i.e. α/βIS-Ni(OH)2) and ε-modification of MnO2. The multiphase hydroxide/oxide composites are prepared by the conventional grinding of α/βIS-Ni(OH)2 and ε-MnO2 and by the in-situ formation after the reaction of layered Na0.5Ni0.5Mn0.5O2 with mixed LiOH-KOH electrolyte. The structure, morphology and porous texture properties of composites are analyzed by means of powder X-ray diffraction, scanning electron microscopy (SEM) and low-temperature nitrogen adsorption, respectively. The electrochemical performance of composites electrodes is determined by galvanostatic experiments in concentrated individual KOH and mixed LiOH-KOH electrolytes. The ex-situ X-ray diffraction is used to monitor the changes in composite electrodes during electrochemical cell function. It has been found that α/βIS-Ni(OH)2 participates in electrochemical reaction concomitantly with H2O and Li+ intercalation, while the electrochemical performance of ε-MnO2 is determined by surface adsorption of electrolyte alkaline ions. The best electrochemical performance (in terms of discharge capacity, rate capability and cycling stability) is achieved for α/βIS-Ni(OH)2 especially when it works in mixed LiOH-KOH electrolyte. In alkaline electrolyte solution, layered Na0.5Ni0.5Mn0.5O2 is transformed into a phase mixture between slightly sodium deficient oxide Na0.5-xNi0.5Mn0.5O2 and α-type nickel hydroxide. Thus generated multiphase composite demonstrates the highest areal capacitance and a rate capability comparable with that for α/βIS-Ni(OH)2.

    更新日期:2018-07-12
  • The role of internal cathodic support during the crevice corrosion of Ni-Cr-Mo alloys
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    J.D. Henderson, N. Ebrahimi, V. Dehnavi, M. Guo, D.W. Shoesmith, J.J. Noël

    Coupling of metal oxidation in crevice corrosion to both O2 reduction on surfaces external to the crevice and H+ reduction occurring within the crevice, was studied using a galvanostatic crevice corrosion technique in conjunction with weight loss analyses. Results suggest internal H+ reduction is a significant contributor to the crevice corrosion of the studied alloys in 5 M NaCl at 120 °C. Repeat experiments suggest damage can be as much as doubled by H+ reduction. This process, however, can be minimized by alloying additions of Mo, which permit the deposition of Mo-rich corrosion products within an active crevice. Due to difficulties experienced during corrosion product removal, the results presented herein are anticipated to be underestimates of the actual extent of this process. Consequently, damage predictions based on the availability of O2 and other oxidants in the service environment may significantly underestimate the actual extent of corrosion on Ni-Cr-Mo alloys.

    更新日期:2018-07-12
  • The effect of wetting area in carbon paper electrode on the performance of vanadium redox flow batteries: A three-dimensional lattice Boltzmann study
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Duo Zhang, Qiong Cai, Oluwadamilola O. Taiwo, Vladimir Yufit, Nigel P. Brandon, Sai Gu

    The vanadium redox flow battery (VRFB) has emerged as a promising technology for large-scale storage of intermittent power generated from renewable energy sources due to its advantages such as scalability, high energy efficiency and low cost. In the current study, a three-dimensional(3D) Lattice Boltzmann model is developed to simulate the transport mechanisms of electrolyte flow, species and charge in the vanadium redox flow battery at the micro pore scale. An electrochemical model using the Butler-Volmer equation is used to provide species and charge coupling at the surface of active electrode. The detailed structure of the carbon paper electrode is obtained using X-ray Computed Tomography(CT). The new model developed in the paper is able to predict the local concentration of different species, over-potential and current density profiles under charge/discharge conditions. The simulated capillary pressure as a function of electrolyte volume fraction for electrolyte wetting process in carbon paper electrode is presented. Different wet surface area of carbon paper electrode correspond to different electrolyte volume fraction in pore space of electrode. The model is then used to investigate the effect of wetting area in carbon paper electrode on the performance of vanadium redox flow battery. It is found that the electrochemical performance of positive half cell is reduced with air bubbles trapped inside the electrode.

    更新日期:2018-07-12
  • A high-performance, all-textile and spirally wound asymmetric supercapacitors based on core–sheath structured MnO2 nanoribbons and cotton-derived carbon cloth
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Caichao Wan, Yue Jiao, Daxin Liang, Yiqiang Wu, Jian Li

    An increasing emphasis on green chemistry and high-efficient utilization of natural resources has raised more demands for more facile, rapid and cost-effective approaches for preparation of energy-storage equipment. Herein, we demonstrate a simple, fast and cheap approach to create a core–sheath structured textile electrode based on cotton-derived carbon cloth (CDCC, core) and MnO2 nanoribbons (sheath). A good interface bonding between the in-situ grown MnO2 and carbon fibers of CDCC aided electron transfer. The abundant MnO2 nanostructures increased electrochemically active areas accessed by electrolyte ions and the porous CDCC acted as an electrolyte reservoir to shorten ion-diffusion path and facilitate efficient infiltration of electrolyte ions. Because of these advantages, the MnO2/CDCC electrode exhibited a high areal capacitance of 202 mF cm−2. In addition, the flexible electrode was assembled into an all-textile and spirally wound asymmetric supercapacitor with an outstanding electrochemical activity, like a high areal energy density of 30.1 μW h cm−2 at 0.15 mW cm−2 and an excellent capacitance retention of 87.7% after 5000 cycles. Another meritorious contribution is the synthetic strategy realizing a more direct, eco-friendly and efficient utilization way of cellulose resource, which avoided pollutions from cellulose purification or pretreatment.

    更新日期:2018-07-12
  • Free-standing Ni-Co alloy nanowire arrays: Efficient and robust catalysts toward urea electro-oxidation
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Xuesen Gao, Yining Wang, Wen Li, Fei Li, Hamidreza Arandiyan, Hongyu Sun, Yan Chen

    Free-standing Ni-Co alloy nanowire arrays are synthesized via a modified template-assisted electrodeposition method. The structure and composition analysis have been performed by employing X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The highly ordered nanowire arrays show a strong adherence to an alloy transition layer. Herein, the alloy nanowire arrays show higher electrocatalytic activity in terms of lower onset potential and higher peak current density compared to the sample synthesized by conventional deposition route for urea electro-oxidation. Moreover, the electrocatalytic activity can be facilely optimized by selecting the length of nanowire arrays (or the deposition time). The best sample deposited with a time of 600 s possesses an onset oxidation potential of 0.372 V (vs. Hg/HgO) and a peak current density of 322.82 mA cm−2 in 1 M KOH and 0.33 M urea solutions. The sample also shows good stability and activity even after sonication treatment. The excellent electrocatalytic properties of urea oxidation are considered due to the one-dimensional free-standing nanoscale alloy structure, which can largely boost the active sites, facilitate charge transfer, and improve the duration of urea electro-oxidation.

    更新日期:2018-07-12
  • Excellent room-temperature performance of lithium metal polymer battery with enhanced interfacial compatibility
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Chuankai Fu, Shuaifeng Lou, Yi Cao, Yulin Ma, Chunyu Du, Pengjian Zuo, Xinqun Cheng, Weiping Tang, Yongmin Wu, Yunzhi Gao, Hua Huo, Geping Yin

    Recently, rechargeable lithium metal polymer battery (LMPB) attracts increasing attention because of its high safety and energy density properties. However, the high contact interfacial resistance of solid-state electrode and electrolyte is still an obstacle to satisfy the demand of high current density and long cycle stability, especially at room and lower temperature. Here, we develop a simple and efficient heat treatment method, to improve the interfacial compatibility between electrode and electrolyte in all-solid-state LMPB, successfully realizing workable LMPB at a reduced temperature (30 °C). The LMPB shows excellent cycling performance and rate capability in the voltage range of 2.5–4.2 V. The behavior of Li+ plating/stripping on the surface of lithium metal anode is greatly enhanced. Meanwhile, the interfacial resistance of the LMPB decrease significantly after the heat treatment process.

    更新日期:2018-07-12
  • Graphene wrapped self-assembled Ni0.85Se-SnO2 microspheres as highly efficient and stable electrocatalyst for hydrogen evolution reaction
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Wenqiang Hou, Binjie Zheng, Fei Qi, Jiarui He, Wanli Zhang, Yuanfu Chen

    For the first time, self-assembled graphene/Ni0.85Se-SnO2 (GNS) microspheres, which are constructed by homogenously distribution of Ni0.85Se-SnO2 nanoparticles wrapped by reduced graphene oxide nanosheets, have been synthesized by a facile and low-cost hydrothermal method. Due to the rationally designed nanoarchitecture and the high conductivity of SnO2 and graphene, the GNS electrocatalyst delivers excellent performance for hydrogen evolution reaction (HER): it exhibits a quite low Tafel slope of 35.8 mV dec−1 and a high cathode current density of 25 mA cm−2 at overpotential of 290 mV (vs RHE); it shows outstanding long-term stability even after 1000 CV cycles in acid solution. This study elucidates a rational construction design and a facile large-scale synthesis method of non-precious HER electrocatalysts with excellent HER performance to replace Pt-based electrocatalysts.

    更新日期:2018-07-12
  • Phase conversion of Pt3Ni2/C from disordered alloy to ordered intermetallic with strained lattice for oxygen reduction reaction
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Lingxuan Chen, Jing Zhu, Jie Wang, Weiping Xiao, Wen Lei, Tonghui Zhao, Ting Huang, Ye Zhu, Deli Wang

    Tuning the surface strain and atom arrangement to control the surface chemistry process is one of efficient strategies to enhance the electrocatalytic performance of nanomaterials. This research introduces an ordered Pt3Ni2/C intermetallic nanoparticle as a new type of the Pt-Ni system for the ORR, which is rarely reported at present. Besides, it focuses on the phase conversion of Pt3Ni2/C nanocatalysts from a disordered phase to an ordered phase. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements confirm the formation of ordered face-centered cubic (fcc) type Pt3Ni2/C nanocatalysts with homogeneous particle distribution and average crystallite size of 6.4 nm. The ordered fcc-Pt3Ni2/C exhibits improved electrocatalytic activities toward the oxygen reduction reaction (ORR) in 0.1 M HClO4 and 0.1 M KOH electrolyte when compared with Pt3Ni2/C disordered alloy. Besides, the robust ordered fcc-Pt3Ni2/C showed a smaller activity loss after durability tests in alkaline medium than acid electrolyte. The improved ORR activity and stability could be ascribed to the surface atom arrangement and reasonable surface strain originated from the ordered structure of Pt3Ni2/C nanoparticles relative to the disordered Pt3Ni2/C alloy, forcefully demonstrating that the Pt3Ni2/C intermetallic compound may act as highly efficient ORR electrocatalysts in energy conversion process.

    更新日期:2018-07-12
  • Highly porous polyimide-derived carbon aerogel as advanced three-dimensional framework of electrode materials for high-performance supercapacitors
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Youfang Zhang, Wei Fan, Hengyi Lu, Tianxi Liu

    The hybridization of highly porous carbon materials and battery-type materials is an effective method for achieving supercapacitors with both high energy density and good rate capability. The structure of the carbon substrate should be carefully designed to meet the requirement of good conductivity and good accessibility to electrolyte and ions. In this work, graphene nanoribbon crosslinked polyimide-derived carbon aerogels (a-GCA) with hierarchical porous structures and large specific surface area of 2413.0 m2 g−1 have been first constructed, and then applied as a conductive template for the uniform growth of ultrathin Ni(OH)2 nanosheets. In the obtained Ni(OH)2/a-GCA hybrids, a-GCA can provide open and interconnected channels for rapid diffusion of ions and electrons to access Ni(OH)2 nanosheets for fast Faradaic redox reactions, as well as enhance the stability of Ni(OH)2 nanosheets. Consequently, the optimized Ni(OH)2/a-GCA hybrid exhibits a high specific capacitance of 537.0 C g−1 at a charge/discharge current density of 1 A g−1, excellent rate capacitance retention of 78.4% at 10 A g−1. Moreover, the assembled Ni(OH)2/a-GCA//a-GCA hybrid supercapacitor device delivers a high energy density of 54.8 Wh kg−1 at a powder density of 816 W kg−1. Therefore, the Ni(OH)2/a-GCA hybrid shows great potential as high-performance electrode materials in applications in energy storage device.

    更新日期:2018-07-12
  • Construction of CuS/TiO2 nano-tube arrays photoelectrode and its enhanced visible light photoelectrocatalytic decomposition and mechanism of penicillin G
    Electrochim. Acta (IF 5.116) Pub Date : 2018-07-11
    Qiuling Ma, Huixuan Zhang, Ruonan Guo, Bo Li, Xinyi Zhang, Xiuwen Cheng, Mingzheng Xie, Qingfeng Cheng

    In this present work, a CuS/TiO2 nano-tube arrays photoelectrode employed in environment purification was successfully prepared by an anodization process, with galvanostatic electrodeposition strategy as following method. Meanwhile, morphologies and chemical structures of the resulting photoelectrodes were studied by series of measurements. The results indicated that CuS nanoparticles were successfully assembled on the surface of well-ordered TiO2 nano-tube arrays, which has significantly enhanced the photoelectrocatalyic activity by red-shifting the light absorption to visible region and increasing the photoinduced charge separation efficiency. What's more, when external potential was applied, CuS/TiO2 nano-tube arrays photoelectrode displayed superior photoelectrocatalyic performance for elimination of penicillin G (99.1%) within 150 min visible light illumination. Moreover, the visible light photoelectrocatalyic degradation pathways of PEN G were proposed based on the HPLC-MS/MS measurements, which included decarboxylation and oxidation of the target organic, and finally mineralization to H2O, CO2, NH4+ and NO3−. This study demonstrated that the novel CuS/TiO2 NTAs photoelectrode showed excellent PEC activity, which had great potential in applications of environmental remediation.

    更新日期:2018-07-12
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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