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  • A Robust Aqueous-Processable Polymer Binder for Long-Life, High-Performance Lithium Sulfur Battery
    Energy Storage Mater. (IF 0) Pub Date : 2018-12-11
    Huan Yi, Tu Lan, Yu Yang, Hongbo Zeng, Tian Zhang, Tian Tang, Chaoyang Wang, Yonghong Deng

    The development of lithium sulfur batteries (LSBs) has significantly suffered from the shuttle of lithium polysulfides (LiPS) and drastic volume change of the active materials during cycling processes. The eco-friendly manufacturing of electrodes based on aqueous slurries is highly desirable for practical applications. To address these challenging issues, a novel aqueous-processable polymer, chitosan sulfate ethylamide glycinamide (CSEG), has been developed as the binder for sulfur cathode. The dual-amide structures endow the CSEG with superior LiPS-trapping capability to impede the diffusion and shuttle of LiPS in electrolyte. The CSEG-based sulfur cathodes demonstrate remarkable cycling performances at 1 C for 700 cycles and 6 C for 450 cycles, with only 0.049%, 0.0895% capacity fading per cycle, respectively. More importantly, the cathode achieves excellent rate performance with a capacity of 194.4 mAh g-1 at an ultrahigh current density of 40.26 mA cm-2 (20 C), which takes only 21 seconds for one charge or discharge process. The electrochemical performance of the novel CSEG binder, as demonstrated in this work, is superior to all previously reported aqueous-processable binders for sulfur cathode. Such a breakthrough will greatly improve the development of eco-friendly sulfur cathode, paving new ways for the practical application of next-generation LSBs.

    更新日期:2018-12-11
  • A numerical study of dust deposition effects on photovoltaic modules and photovoltaic-thermal systems
    Renew. Energy (IF 4.9) Pub Date : 2018-12-10
    Ali Salari, Ali Hakkaki-Fard

    Dust deposition on the surface of solar systems is one of the main parameters that significantly affects the performance of such systems. In this study, the effect of dust deposition density on the performance of photovoltaic modules (PV) and photovoltaic-thermal systems (PVT) is numerically investigated. Accordingly, all layers of a monocrystalline silicon PV module for both systems are simulated. Moreover, the effect of various system parameters on the performance of both clean and dusty PV module and PVT system are studied. The studied parameters included: solar radiation intensity, ambient temperature, coolant inlet temperature, and coolant inlet velocity. The obtained results indicate that by increasing the dust deposition density on the surface of the PV module from 0 g/m2 to 8 g/m2, its electrical efficiency reduces by 26.36%. In addition, by increasing the dust deposition density on the surface of the PVT system from 0 g/m2 to 8 g/m2, its electrical and thermal efficiencies reduce by 26.42% and 16.11%, respectively. Moreover, the simulation results show that the effect of considered parameters on the clean solar system is more significant than the dusty system. Furthermore, two correlations for electrical and thermal output reduction as a function of dust deposition density are proposed.

    更新日期:2018-12-11
  • Wind shear effect induced by the platform pitch motion of a Spar-type floating wind turbine
    Renew. Energy (IF 4.9) Pub Date : 2018-12-10
    Binrong Wen, Xinliang Tian, Qi Zhang, Xingjian Dong, Zhike Peng, Wenming Zhang, Kexiang Wei

    The platform pitch motion of a Floating Wind Turbine (FWT) introduces additional relative wind speed to the rotor. This additional relative wind speed distributes linearly along the vertical altitude, which is similar to the linear wind shear, thus it is addressed as the platform-pitch-induced (PPI) wind shear effect. In this paper, the PPI wind shear is investigated numerically with the Free Vortex Method (FVM). Firstly, the typical wind shear and the PPI wind shear are separately analyzed and then compared with each other. The wind profile of the typical wind shear is stationary. However, the wind profile of the PPI wind shear is time-varying, which complicates the aerodynamics of the FWT. Subsequently, the influencing factors of the PPI wind shear are thoroughly discussed. Results show that the PPI wind shear is related to the FWT structures, and it is increased with the increases of the platform pitch amplitude, frequency and the tip speed ratio. The PPI wind shear introduces significant fluctuations to the aerodynamic loads, which smear the power quality and result in potential fatigue damages to the FWT structures. To mitigate the adverse effects of the PPI wind shear, advanced control strategies and optimized structure designs should be developed.

    更新日期:2018-12-11
  • Impact of Policy Mix Concerning Renewable Portfolio Standards and Emissions Trading on Electricity Market
    Renew. Energy (IF 4.9) Pub Date : 2018-12-10
    Xiongjiantao Bao, Wenhui Zhao, Xiaomei Wang, Zhongfu Tan

    Few studies of policy mix concerning renewable portfolio standards (RPS) and emissions trading (ET) investigate a scenario in which the retailer is required to comply with quota obligations. This paper focuses on the impact of RPS, with an ET counterpart, on the electricity market when RPS are imposed on the state grid companies. The evolution game is employed to model transactions between multiple buyers and multiple sellers. The results show that ET enhances the price competitiveness of electricity from renewable energy source (RES-E) and reduces power generating companies’ profit at the same time. On the other hand, when the RPS level goes up, the state grid companies gain a windfall created by the difference between the lower wholesale price of thermal power and the unchanging retail price. The windfall will be used to pay for the increasing cost of supporting RES-E. Thus, the thermal power generating companies are confronted with the double cost when introducing ET and RPS, but the state grid companies do not pay for the cost of supporting RES-E. This paper appeals to the Chinese government for the assessment of policy effects from a policy mix perspective.

    更新日期:2018-12-11
  • Comparative study of air and argon gases between cover and absorber coil in a cylindrical solar water heater: An experimental study
    Renew. Energy (IF 4.9) Pub Date : 2018-12-11
    Gholamabbas Sadeghi, Habibollah Safarzadeh, Mehdi Bahiraei, Mehran Ameri, Mohsen Raziani

    In this study, the effect of various gases filling the space between the cover and the absorber coil on the thermal performance of a cylindrical solar water heater (CSWH) is experimentally investigated. Since the Prandtl number for argon gas is less than that for the air, the thermal performance of the CSWH increases. The experiments are conducted for mass flow rates of 2.5, 3, 3.5 and 4 kg/h. The results show that an increase in the flow rate leads to a decrease in the temperature difference the of water between the inlet and outlet of the coil due to reduction of the residence time of the fluid. The energy efficiency of the collector reaches its maximum at the mass flow rate until 3.5 kg/h, and then reduces at higher values of mass flow rate because the water temperature difference decreases dramatically. Hence, the optimum mass flow rate for a cylindrical collector is reported as 3.5 kg/h. The maximum energy efficiencies for argon and air are 52.14% and 48.17%, respectively. Finally, the constructed cylindrical solar water heater is also economically compared to a flat plate collector (FPC) and an electric water heater with similar thermal efficiency.

    更新日期:2018-12-11
  • Investigation of gas slippage effect and matrix compaction effect on shale gas production evaluation and hydraulic fracturing design based on experiment and reservoir simulation
    Fuel (IF 4.908) Pub Date : 2018-12-10
    Courtney Rubin, Mehrdad Zamirian, Ali Takbiri-Borujeni, Ming Gu

    Recent core-lab study of Marcellus Shale illustrated that effect of gas slippage and matrix compaction are significant on gas production because of substantial reservoir pressure depletion, especially during the late time of gas production. However, the impact of gas slippage and matrix compaction on gas recovery evaluation and hydraulic fracturing design is still not clearly understood and systematically investigated. Additionally, such impact varies with production time and completion/production circumstances. Therefore, it is critical to develop a laboratory-modeling based approach that properly characterizes the two permeability effects and evaluates their impact on well production evaluation and hydraulic fracturing design. In this study, a comprehensive parametric study is conducted by running reservoir simulations using empirical permeability correlations developed from core-lab tests under different confining stress and pore pressure conditions. Simulations of different case scenarios are run in two contrast groups. One group considers the effect of gas slippage and matrix compaction on gas production and the other group ignores the two effects. By comparing the simulated gas production, critical conductivity, and proppant pumping amount/cost of the two contrast groups, a better understanding of the effect of gas slippage and geomechanics on shale gas well performance and hydraulic fracturing design can be developed for operators. The results show that ignoring the two permeability effect in reservoir simulation leads to an overestimation of gas production evaluation, which is up to 11% for Marcellus Shale. It also leads to an over-design of proppant pumping amount, resulting in early staging, screening-out, and excessive pumping cost. Calculations further show that, an average of over 2 million dollars can be wasted for fracturing a single horizontal well in Marcellus Shale if excluding the two effect from a fracturing design. The two effects are more significant for lower BHP, longer hydraulic fracture, and larger stage spacing conditions.

    更新日期:2018-12-11
  • Rapid fabrication of KTa0.75Nb0.25/g-C3N4 composite via microwave heating for efficient photocatalytic H2 evolution
    Fuel (IF 4.908) Pub Date : 2018-12-10
    Zhiqiang Chen, Pengfei Chen, Pingxing Xing, Xin Hu, Hongjun Lin, Leihong Zhao, Ying Wu, Yiming He

    A novel KTa0.75Nb0.25O3 (KTN)/g-C3N4 composite photocatalyst was fabricated through microwave heating for realizing the efficient photocatalytic H2 evolution. The energy-efficient preparation method allowed g-C3N4 to be formed in-situ on KTN surface in thirty five minutes. The binary constitution of the KTN/g-C3N4 composite was verified by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) experiments. UV–visible diffuse reflection spectroscopy (DRS) experiments suggested that the photoabsorption performance was increased after the introduction of KTN. N2-adsorption analysis indicated that the addition of KTN slightly increased the surface area of g-C3N4. Photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS) and transient photocurrent response (PC) analyses confirmed that the KTN/g-C3N4 composite displayed longer lifetime of photoexcited charge carriers than g-C3N4, owing to the suitable band potentials and the close contact of KTN and g-C3N4. This property was believed to the key characteristic of the composite, which led to its excellent photocatalytic performance. Under simulated sunlight irradiation, the optimal KTN/g-C3N4 catalyst presented a photocatalytic H2-generation rate of 1673 μmol·g−1·h−1, 2.5 and 2.4 times higher than that of KTN and pure g-C3N4, respectively. Under visible light irradiation, the value was determined to be 86.2 μmol·g−1·h−1, which achieved 9.3 times that of g-C3N4.

    更新日期:2018-12-11
  • Fuel adhesion characteristics under non-evaporation and evaporation conditions: Part 1-effect of injection pressure
    Fuel (IF 4.908) Pub Date : 2018-12-10
    Hongliang Luo, Keiya Nishida, Youichi Ogata, Wu Zhang, Tatsuya Fujikawa

    Spray-wall impingement has been proved unavoidable in direct-injection spark-ignition (DISI) engines, which affects the fuel-air formation as well as combustion and exhaust emissions, making it difficult to meet the regulation of particle number (PN) in the future standards. In this study, the characteristics of fuel adhesion injected by a mini-sac gasoline injector with a single hole were investigated in a constant high-pressure chamber. The fuel spray and adhesion were measured via Mie scattering and refractive index matching (RIM) methods, respectively. The effect of injection pressure on the spray-wall interaction under room and high temperature condition were tested. The results showed that under room temperature, the injection pressure promotes better atomization, resulting in longer spray tip penetration, larger impinging spray height, and more fuel adhesion on the wall. However, when evaporation occurs, higher injection pressure favors the fuel evaporation due to the small droplets size, leading to shorter spray tip penetration, smaller impinging spray height, and less fuel adhesion on the wall. Moreover, under non-evaporation condition, high injection pressure has less effect on the uniformity of the fuel adhesion on the wall, while under evaporation condition, it improves the uniformity of the fuel adhesion. Owing to the different mechanisms of the fuel adhesion formation in the primary impingement (Region I) and secondary impingement (Region II) regions, injection pressure has more influence on the fuel adhesion in Region I, especially under evaporation condition.

    更新日期:2018-12-11
  • Unique ion diffusion properties in lead-free halide double perovskites: A first-principles study
    J. Power Sources (IF 6.945) Pub Date : 2018-12-11
    Jian Xu, Jian-Bo Liu, Bai-Xin Liu, Bing Huang

    Pb-free halide double perovskites (HDPs) are proposed as potential candidates for various optoelectronic applications to replace the mainstream hybrid organic-inorganic halide perovskites, e.g., CH3NH3PbI3. While it is known that ion diffusion is a critical problem to affect the structural and electronic stability of CH3NH3PbI3, the mechanism of ion diffusions in HDPs is still unclear and highly desired to be revealed. In this study, taking Cs2AgInX6 (X = Cl, Br) HDPs as prototypes, for the first time we suggest that the fast ion diffusion of the dominant defects may play an important role in the performance stability of HDPs. Importantly, we find that the Agi+ diffusion in a multi-ion concerted fashion has a much faster diffusion rate, compared to the VAg− and VX+ diffusion in a single-ion fashion. It is revealed that HDPs exhibit quite different diffusion properties from CH3NH3PbI3. Furthermore, we demonstrate that the diffusion rate of Agi+ in HDPs can be effectively suppressed by applying an epitaxial strain, which opens a promising way to enhance the performance stability of perovskite materials for various device applications.

    更新日期:2018-12-11
  • Feasibility of activated carbon derived from anaerobic digester residues for supercapacitors
    J. Power Sources (IF 6.945) Pub Date : 2018-12-11
    Ce Wang, Jin Wang, Wentao Wu, Jiang Qian, Shaomin Song, Zhengbo Yue

    The question of how to recycle anaerobic digester residue is a critical issue for the anaerobic digestion process of lignocellulosic biomass. In the current study, anaerobic digester residue from a biogas plant for the treatment of cattle manure was utilized to prepare the activated carbon for supercapacitors. The effect of activation temperature on the specific surface area, pore size distribution, and electrochemical performance of activated carbon was investigated. Results show that activated carbon derived from anaerobic digester residue is feasible for supercapacitors. With an increase in activation temperature, the specific surface area of activated carbon first increases and then gradually decreases. Activated carbon obtained at 700 °C shows both high specific capacitance and excellent electrochemical cycle stability. The good capacitive performance confirms that anaerobic digested manure residue can act as an excellent carbonaceous material for high-performance supercapacitors.

    更新日期:2018-12-11
  • High-mass loading electrodes with exceptional areal capacitance and cycling performance through a hierarchical network of MnO2 nanoflakes and conducting polymer gel
    J. Power Sources (IF 6.945) Pub Date : 2018-12-10
    Zhaokun Yang, Jun Ma, Sherif Araby, Dongjian Shi, Weifu Dong, Ting Tang, Mingqing Chen

    Engineering electroactive materials onto 3D conductive scaffolds holds promise to the development of high-performance energy storage devices. In comparison with the existing scaffolds made of metals or carbon nanomaterials, we herein report a unique scaffold of 3D nanostructured polyaniline (PANi) network, where MnO2 nanoflakes of 10 nm in thickness grow vertically to create a hierarchically structured composite. Through two simple sequential processes, a binder-free electrode with a high areal density of 8.3 mg cm−2 (7.3 for MnO2 and 1.0 for PANi) is readily fabricated by using a piece of carbon cloth as the current collector. Measured with three-electrode configuration at 5 mV s−1, the network delivers capacitance of 423.7 F g−1, 3516.7 mF cm−2 and 106.6 F cm−3, with retention of 98.5% over 10,000 cycles. The high capacitance especially areal capacitance is attributed to the maximum utilization of high-specific area MnO2 nanoflakes through efficient electron and ion transfer which is enabled by two intimate interfaces respectively between MnO2 and PANi and between PANi and carbon cloth. The superior cycling performance is mainly enabled by the volume-change accommodation of the hierarchically porous network. This composite network would provide a new methodology to maximize the electrochemical performance of metal oxides.

    更新日期:2018-12-11
  • Investigation of oxide ion flux at cathode/electrolyte interface in solid oxide fuel cell
    J. Power Sources (IF 6.945) Pub Date : 2018-12-11
    Tsuyoshi Nagasawa, Katsunori Hanamura

    Oxide ion flux at cathode/electrolyte interface of solid oxide fuel cell (SOFC) is investigated through quenching reaction and oxygen isotope labeling. A YSZ (yttria-stabilized zirconia) electrolyte-supported cell with LSM (strontium-doped lanthanum manganite)/YSZ porous cathode is operated by supplying 18O2 at 973 K and abruptly quenched to room temperature by a direct helium gas-impinging jet to the cell. The 18O concentration distribution in the cross section of the cathode/electrolyte interface is obtained by secondary ion mass spectrometry (SIMS) with a spatial resolution of 50 nm. From the analysis of oxygen isotope diffusion profiles in YSZ electrolyte, oxide ion flux incorporated from a cathode/electrolyte interface to an electrolyte is first estimated. The obtained flux 1.01–1.43 × 10−3 mol m−2 s−1 at a current density of 0.09 A cm−2 indicates that 22–31% of the overall electrochemical reaction occurs at the cathode/electrolyte interface, while the remaining 69–78% of those proceeds inside the porous cathode under the present experimental condition.

    更新日期:2018-12-11
  • Fabrication of high-performance proton-conducting electrolytes from microwave prepared ultrafine powders for solid oxide fuel cells
    J. Power Sources (IF 6.945) Pub Date : 2018-12-11
    Bin Wang, Xuehua Liu, Lei Bi, X.S. Zhao

    The microwave sintering method is found to have advantages over the conventional thermal treatment method for preparing BaZr0.1Ce0.7Y0.2O3-δ powder. Comparing with the conventional thermal treatment, the microwave sintering method allows the solid material to be self-heated, enabling the formation of pure phase BaZr0.1Ce0.7Y0.2O3-δ powder at a relatively low temperature (900 °C) with a short dwell time of 1 h, while the same pure phase can only be formed at 1000 °C in an electric furnace. Importantly, the grain size for the microwave prepared BaZr0.1Ce0.7Y0.2O3-δ powder is much smaller than that of the conventionally thermal treated BaZr0.1Ce0.7Y0.2O3-δ powder. The small powder grain size is found to be beneficial for the densification and grain growth of the resultant electrolyte membrane during the electrolyte sintering procedure. A fuel cell fabricated using this electrolyte membrane with a conductivity of 7 × 10−3 S cm−1 delivers a power output of 791 mW cm−2 at 700 °C.

    更新日期:2018-12-11
  • In-situ and selectively laser reduced graphene oxide sheets as excellent conductive additive for high rate capability LiFePO4 lithium ion batteries
    J. Power Sources (IF 6.945) Pub Date : 2018-12-11
    Jun Tang, Xiongwei Zhong, Haiqiao Li, Yan Li, Feng Pan, Baomin Xu

    We report an ultrafast in-situ laser reduction process of graphene oxides (GO) in LiFePO4 electrodes, where the selective laser reduction of GO sheets is conducted after coating LiFePO4 on current collector. This novel process technique avoids the solvophobicity and agglomeration problems of graphene in 1-methyl-2-pyrrolidinone (NMP) or other solvents for the electrode material slurry preparation because of GO's solvophilicity in various solvents. Under the optimized laser reduction condition, a hierarchical structure of graphene conductive network is formed without wrapping the LiFePO4 surface, which can greatly improve the rate capability and cycle performance. The battery capacity remains 84.5% after 1000 cycles and 72.9% when the charge/discharge current density increases from 0.5C to 20C. The method developed in this work is also applicable for other material systems to selectively reduce GO for performance enhancement.

    更新日期:2018-12-11
  • Sulfurized−poly(acrylonitrile) wrapped carbonsulfur composite cathode material for high performance rechargeable lithiumsulfur batteries
    J. Power Sources (IF 6.945) Pub Date : 2018-12-11
    Chung−Feng Jeffrey Kuo, Misganaw Adigo Weret, Hui−Yu Hung, Meng−Che Tsai, Chen−Jui Huang, Wei−Nien Su, Bing−Joe Hwang

    Sulfurized−poly(acrylonitrile) composite cathode materials provide high specific capacity, deprive the dissolution of polysulfides and shuttling effect. However, these materials have intrinsic problems such as low sulfur loading and poor rate capability at high C−rate due to the moderate conductivity of the composites. Here, we synthesize a wrapped S/rSP@SPAN composite using a dissolution−reprecipitation method followed by the thermal treatment. The idea is that the dissolution−reprecipitation of SP@PAN augments the surface area of the composite, which provides high sulfur loading and improves the composite−electrolyte contact, and conductivity of cathode material. As a result, the electrochemical performance of the as−fabricated S/rSP@SPAN cathode material yields excellent cyclability and high rate capability of 492 mAh g−1 even at a high C−rate (10 C) with high sulfur loading (54.5%).

    更新日期:2018-12-11
  • Nanostructured ternary metal chalcogenide-based binder-free electrodes for high energy density asymmetric supercapacitors
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Vimal Kumar Mariappan, Karthikeyan Krishnamoorthy, Parthiban Pazhamalai, Surjit Sahoo, Swapnil Shital Nardekar, Sang -Jae Kim

    An essential way to enhance the energy density of a supercapacitor(SC) is to use high capacitance electrode materials via developing binder-free electrode with porous and hierarchical nanostructures. Herein, we demonstrated the use of copper antimony sulfide (Cu3SbS4) nanowires directly grown on Ni foam (using a microwave-irradiation process) as a binder-free positive electrode for SCs. The growth mechanism and effect of microwave irradiation time on the morphology and electrochemical properties of Cu3SbS4 on Ni foam were discussed in detail. The cyclic voltammetric studies (using three-electrode test) of Cu3SbS4/Ni-5 electrode showed the presence of Type-C battery-like charge-storage properties. The Cu3SbS4/Ni-5 electrode delivered a high specific capacity (835.24 mAh g−1) as obtained from the charge-discharge analysis (at a current density of 2.5 mA cm−2). Further, the device specific properties of the Cu3SbS4/Ni-5 positive electrode was examined via fabricating asymmetric supercapacitors (ASCs) using two different negative electrodes viz. (i) planar-graphene, and (ii) binder-free copper molybdenum sulfide anchored on Ni foam (Cu2MoS4/Ni) electrodes, respectively. The electrochemical analyses of the fabricated ASCs revealed that the Cu3SbS4/Ni-5║Cu2MoS4/Ni ASC possess almost 3.0-fold higher energy density compared to the Cu3SbS4/Ni-5║graphene ASC. The Cu3SbS4/Ni-5║Cu2MoS4/Ni ASC delivered a high specific device capacitance of 213.6 F g−1 with a remarkable energy density (58.15 Wh kg−1), maximum power density (6363.63 W kg−1), and better cycle-life. The use of two different binder-free electrodes in the Cu3SbS4/Ni-5║Cu2MoS4/Ni ASC results in their superior performance metrics over the reported ASCs, thus, highlighting their potential applications towards next-generation supercapacitors.

    更新日期:2018-12-11
  • Synergistically Well-Mixed MOFs Grown on Nickel Foam as Highly Efficient Durable Bifunctional Electrocatalysts for Overall Water Splitting at High Current Densities
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Duraisamy Senthil Raja, Hao-Wei Lin, Shih-Yuan Lu

    Metal-organic framework (MOF), possessing versatile catalytic activities, remarkable structural diversity, high surface areas, and tunable pore sizes, was recently demonstrated an outstanding catalyst for electrolytic water splitting. The electrolytic performances can be much enhanced with a synergistic design of the MOFs, which was realized as uniformly well-mixed and dispersed Fe- and Ni-MOFs (termed as MFN-MOFs) in-situ grown on backbones of nickel foam (NF). The electrocatalyst thus developed exhibited ultra-high activities at high current densities for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH, delivering 10 and 500 mA cm−2 at ultralow overpotentials of 79 and 234 mV, respectively with a small Tafel slope of 30.1 mV dec−1 for the HER and achieving ultralow overpotentials of 235 and 294 mV for the OER at 50 and 500 mA cm−2, respectively with a small Tafel slope of 55.4 mV dec−1. The inter-molecular synergistic interactions between the well-mixed and dispersed Fe- and Ni-MOFs not only facilitate the critical charge transfer for the redox reactions but also disperse the active metal ion sites to enhance their degree of utilization to achieve exceptional OER and HER performances. The MFN-MOFs/NF//MFN-MOFs/NF couple exhibited ultralow cell voltages of 1.495 V@10 mA cm−2 and 1.80 V@500 mA cm−2 with a Tafel slope of only 79.5 mV dec−1 in 1 M KOH, outperforming most of the state-of-the-art bifunctional electrode couples and benchmark couple of Pt-C/NF//IrO2/NF. More importantly, the MFN-MOFs/NF electrode exhibited ultrastability at high current densities, with a minor decay of 3.7% in a chronopotentiometric stability test conducted at a commercially viable high current density of 500 mA cm−2 for overall water-splitting over 100 h. This synergistic effect boosting design concept for electrocatalysts was successfully demonstrated, opening up a new way for catalyst design toward large-scale H2 production.

    更新日期:2018-12-11
  • Surface potential tailoring of PMMA fibers by electrospinning for enhanced triboelectric performance
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Tommaso Busolo, Daniel P. Ura, Sung Kyun Kim, Mateusz M. Marzec, Andrzej Bernasik, Urszula Stachewicz, Sohini Kar-Narayan

    Triboelectric generators rely on contact-generated surface charge transfer between materials with different electron affinities to convert mechanical energy into useful electricity. The ability to modify the surface chemistry of polymeric materials can therefore lead to significant enhancement of the triboelectric performance. Poly(methyl methacrylate) (PMMA) is a biocompatible polymer commonly used in medical applications, but its central position on the triboelectric series, which empirically ranks materials according to their electron-donating or electron accepting tendencies, renders it unsuitable for application in triboelectric generators. Here, we show that the surface potential of PMMA fibers produced by electrospinning can be tailored through the polarity of the voltage used during the fabrication process, thereby improving its triboelectric performance, as compared to typically spin-coated PMMA films. The change in surface chemistry of the electrospun PMMA fibers is verified using X-ray photoelectron spectroscopy, and this is directly correlated to the changes in surface potential observed by Kelvin probe force microscopy. We demonstrate the enhancement of triboelectric energy harvesting capability of the electrospun PMMA fibers, suggesting that this surface potential modification approach can be more widely applied to other materials as well, for improved triboelectric performance.

    更新日期:2018-12-11
  • Au@HgxCd1-xTe Core@Shell Nanorods by Sequential Aqueous Cation Exchange for Near-Infrared Photodetectors
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Xinyuan Li, Muhammad Ahsan Iqbal, Meng Xu, Yi-Chi Wang, Hongzhi Wang, Muwei Ji, Xiaodong Wan, Thomas J.A. Slater, Jia Liu, Jiajia Liu, Hongpan Rong, Wenxing Chen, Stephen V. Kershaw, Sarah J. Haigh, Andrey L. Rogach, Liming Xie, Jiatao Zhang

    We have explored the synthesis of Au@HgxCd1-xTe core@shell nanorods by sequential aqueous cation exchange (ACE) for near-infrared photodetector application. A number of related Au@telluride core/shell nanorod structures were put forwarded, taking advantage of multi-step transformations through a binary and then a ternary phase for the telluride shells. The latter have a high degree of crystallinity thanks to the step-wise ACE method. The use of only trace amounts of Cd2+ coordinated with tri-n-butylphosphine, assisted the phase transformation from an amorphous Ag2Te shell to a highly crystalline Ag3AuTe2 shell in the first stage; this was followed by a further cation exchange (CE) step with far higher Cd2+ levels to fabricate a highly crystalline CdTe shell, and with an additional CE with Hg2+ to convert it to a HgxCd1-xTe shell. The composition of the shell components and the well-controlled thickness of the shells enabled tunable surface plasmon resonance properties of the Au@telluride nanorods in the NIR region. Utilizing the enhanced NIR absorption, a hybrid photodetector structure of Au@HgxCd1-xTe nanorods on graphene was fabricated, showing visible to NIR (vis-NIR) broadband detection with high photoresponsivity (~106 A/W).

    更新日期:2018-12-11
  • Fundamental research on the effective contact area of micro-/nano-textured surface in triboelectric nanogenerator
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Weixu Yang, Xiaoli Wang, Hanqing Li, Jun Wu, Yanqiang Hu, Zhihao Li, Hui Liu

    The triboelectric nanogenerator (TENG) is a new energy technology to convert mechanical energy into electricity based on contact electrification and electrostatic induction. An effective way to improve power generation of TENG is to increase the effective contact area through introducing micro-/nano-textures onto the contact surface. However, the definition and quantitative analysis on the “effective” contact area of micro-/nano-textures is still in doubt so that the design of surface texture to improve the output of TENG is lack of theoretical basis. In this paper, an adhesive contact model considering textures is established, and the computational methods such as inexact Newton method, bi-conjugate stabilized (Bi-CGSTAB) method and fast Fourier transform (FFT) technique are employed to quantitatively analyze the effects of applied force and texture size on the effective contact area and open-circuit voltage. On the other hand, the pyramid textured surfaces of TENG are fabricated through lithography, wet etching and replication techniques, the test platforms of contact area and electrical output for TENGs are constructed as well, and results from simulation and experiment are compared at last. It is shown that, firstly, the four sides of pyramid texture are involved in the contact electrification and therefore the effective contact area should be the sum of the pyramid lateral area involved in contact when contact only happens in texture region, or the sum of pyramid lateral area and flat area involved in contact when contact happens in both texture and flat regions. Secondly, under lighter loading, the open-circuit voltage of TENGs with pyramid textures increases due to the increase of contact area, while under heavier loading, the open-circuit voltage remains stable due to the unchanged contact area. In addition, the contact area and open-circuit voltage of TENGs will increase with increased texture pitch under lighter applied force while decrease with increased texture pitch under heavier applied force. This study reveals the correlation between the contact area and electrical performance of TENG with textured surfaces and provides theoretical basis for texture design of TENG.

    更新日期:2018-12-11
  • Enhanced Photocurrent in InGaN/GaN MQWs Solar Cells by Coupling Plasmonic with Piezo-Phototronic effect
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Chunyan Jiang, Yan Chen, Jiangman Sun, Liang Jing, Mengmeng Liu, Ting Liu, Yan Pan, Xiong Pu, Bei Ma, Weiguo Hu, Zhong Lin Wang

    InGaN-based photovoltaics (PV) devices have attracted great attentions because of the excellent photoelectric performance over the past decades. The photocurrent of the InGaN/GaN MQWs solar cells could be further improved by coupling plasmonic with piezo-phototronic effect. Here, we fabricated an InGaN/GaN MQWs solar cells with Ag nanoparticles and the short circuit current of the solar cell was improved by 40% with a static external strain applied. The transmission spectrum and the electromagnetic field distributions of the nanoparticles array were simulated with a finite element analysis model. The physical mechanism for light absorption enhancement by the coupling effect in the quantum well structures was illuminated through a self-consistent numerical calculation with non-linear piezoelectricity polarization. This work demonstrated the coupling between the plasmonic and piezo-phototronic effect achieves significant increase in InGaN/GaN MQWs solar cell power conversion efficiency without any complicated process involved.

    更新日期:2018-12-11
  • Efficient Quantum Dots Anchored Nanocomposite for Highly Active ORR/OER Electrocatalyst of Advanced Metal-Air Batteries
    Nano Energy (IF 13.12) Pub Date : 2018-12-11
    Nengneng Xu, Yanxing Zhang, Tao Zhang, Yuyu Liu, Jinli Qiao

    High activity bifunctional non-noble electrocatalysts, targeting both ORR and OER, are rationally designed by integrating the merits of both NiFe2O4 quantum dots and carbons nanotubes (CNTs) (NiFe2O4(QDs)/CNTs), which possesses large specific surface area (584 m2 g-1), abundant NiFe2O4 quantum dots and superior conductivity. Specially, the mechanism for the formation of quantum dots in relation to Fe/Ni ratio and the corresponding activity of ORR and OER are studied carefully. Consequently, NiFe2O4(QDs)/CNTs exhibits superior bifunctional oxygen electrocatalytic activities with the lowest the potential difference (ΔE) of 0.9 V, outperforming well-known commercial Pt/C and IrO2, directly demonstrating the advantages of quantum dots catalysts on providing more effective actives sites and adsorption-desorption sites to promote oxygen reaction kinetics. NiFe2O4(QDs)/CNTs, as high-performance catalyst used in liquid and flexible metal-air batteries, realize high power density, high specific capacity, long-term rechargeability (over 800 hours), and extremely low charge-discharge voltage gaps (only 0.62 V) in ambient atmosphere. Furthermore, the metal-air batteries with flexible configuration effectively prevent the migration of Zn2+/Mg2+, the production of carbonate and the hydrogen evolution reaction. Density functional theory calculations further illustrate that the NiFe2O4(QDs) on CNT has a very active ORR and OER site at the interface Ni site. The work offers prospects for the rational design of quantum dots containing composites to achieve their practicalities in next generation of metal-air batteries.

    更新日期:2018-12-11
  • Resilience in numbers
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10
    Fouad Khan

    Resilience in numbers Resilience in numbers, Published online: 10 December 2018; doi:10.1038/s41560-018-0302-1 Resilience in numbers

    更新日期:2018-12-11
  • Technological, economic and environmental prospects of all-electric aircraft
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10
    Andreas W. Schäfer, Steven R. H. Barrett, Khan Doyme, Lynnette M. Dray, Albert R. Gnadt, Rod Self, Aidan O’Sullivan, Athanasios P. Synodinos, Antonio J. Torija

    Ever since the Wright brothers’ first powered flight in 1903, commercial aircraft have relied on liquid hydrocarbon fuels. However, the need for greenhouse gas emission reductions along with recent progress in battery technology for automobiles has generated strong interest in electric propulsion in aviation. This Analysis provides a first-order assessment of the energy, economic and environmental implications of all-electric aircraft. We show that batteries with significantly higher specific energy and lower cost, coupled with further reductions of costs and CO2 intensity of electricity, are necessary for exploiting the full range of economic and environmental benefits provided by all-electric aircraft. A global fleet of all-electric aircraft serving all flights up to a distance of 400–600 nautical miles (741–1,111 km) would demand an equivalent of 0.6–1.7% of worldwide electricity consumption in 2015. Although lifecycle CO2 emissions of all-electric aircraft depend on the power generation mix, all direct combustion emissions and thus direct air pollutants and direct non-CO2 warming impacts would be eliminated.

    更新日期:2018-12-11
  • Turn up the heat
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10

    Turn up the heat Turn up the heat, Published online: 10 December 2018; doi:10.1038/s41560-018-0305-y Mounting calls for action on low-carbon heating and cooling systems are welcome, but we must move beyond only talking about it.

    更新日期:2018-12-11
  • Hydrogen generation from solid state NaBH4 by using FeCl3 catalyst for portable proton exchange membrane fuel cell applications
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-10
    Aslı Boran, Serdar Erkan, Inci Eroglu

    Being a boron-based compound, sodium borohydride, NaBH4, is a convenient hydrogen storage material for applications like unmanned air vehicles. There are several concerns behind commercialization of hydrogen gas generator by NaBH4 hydrolysis systems. This study aims to contribute to the solution of the problems of NaBH4 hydrolysis system in three main ways. First, the usage of solid state NaBH4 enables to increase the durability and the gravimetric H2 storage capacity of the system in order to meet US DOE targets. Second, solid NaBH4 usage decreases the system's weight since it does not require a separate fuel storage tank, which is very important for portable, on demand applications. Finally, the system's cost is decreased by using an accessible and effective non-precious catalyst such as ferric chloride, FeCl3. The maximum hydrogen generation rate obtained was 2.6 L/min and the yield was 2 L H2/g NaBH4 with an efficiency of 76% at its most promising condition. Moreover, the novel solid NaBH4 hydrogen gas generator developed in the present work was integrated into a proton exchange membrane fuel cell and tested at the optimum operating conditions.

    更新日期:2018-12-11
  • Carbon supported PdM (M = Fe, Co) electrocatalysts for formic acid oxidation. Influence of the Fe and Co precursors
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    L. Juárez-Marmolejo, S. Pérez-Rodríguez, M.G. Montes de Oca-Yemha, M. Palomar-Pardavé, M. Romero-Romo, A. Ezeta-Mejía, P. Morales-Gil, M.V. Martínez-Huerta, M.J. Lázaro

    Pd and PdM (M = Fe or Co) nanostructured electrocatalysts were synthesized by the impregnation method and supported on carbon black Vulcan XC-72R for the formic acid oxidation reaction, FAOR, in acid medium. Nitrates or chlorides were used as Fe and Co precursors to study the counter ion role on the physicochemical features and electrochemical performance of the electrocatalysts. TEM analysis showed that PdM was deposited on the carbon material with a particle size around 2–3 nm. From XRD, peaks associated with the fcc palladium planes were observed along with evidence of PdM alloy formation, particularly when the nitrate salts were used as metal precursors. Furthermore, XPS analyses indicated that nitrates promote the metal oxide formation to a greater extent than chlorides, mainly for Pd. PdCo electrocatalyst obtained from nitrates exhibited the highest performance for FAOR with a steady state current density of 451 and 313 μA cm−2 at 200 and 400 mV respectively, which is in both cases, 3 times larger than that developed for a commercial Pd/C catalyst.

    更新日期:2018-12-11
  • An improved thermal control of open cathode proton exchange membrane fuel cell
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Chaima Mahjoubi, Jean-Christophe Olivier, Sondes Skander-mustapha, Mohamed Machmoum, Ilhem Slama-belkhodja

    Proton exchange membrane fuel cell is a well-known technology that has shown high efficiency and performance as a power system compared to conventional sources such as internal combustion engines. Especially, open cathode proton exchange membrane is growing more popular thanks to its simple structure, low cost and low parasitic losses. However, the open cathode fuel cell performance is highly related to the operating temperature variation and the airflow rate which is adjusted through the fan voltage. In this regard, the present study investigates the thermal management of an open cathode proton exchange membrane fuel cell. The objectives are the stack performance improvement and the stack degradation prevention. Indeed, a safety and optimal operating zone governed by the load current, the stack temperature and the air stoichiometry, is designed. This optimal operating zone is defined based on the system thermal balance and the operating constraints. Hence, the proposed control strategy deals concurrently with the stack temperature regulation and the air stoichiometry adjustment to guarantee the goals achievement. The performance of the proposed control strategy is verified through experimental studies with different operating conditions and results prove its efficiency. To properly design an appropriate control strategy, a multiphysic fuel cell model is developed based on acausal approach by mean of Matlab/Simscape and experimentally validated.

    更新日期:2018-12-11
  • Optimization of fermentative hydrogen production by Enterococcus faecium INET2 using response surface methodology
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Yanan Yin, Jianlong Wang

    A newly isolated strain Enterococcus faecium INET2 was used as inoculum for biohydrogen production through dark fermentation. The individual and interactive effect of initial pH, operation temperature, glucose concentration and inoculation amount on the accumulation of hydrogen during fermentation was examined by a Box–Behnken Design (BBD), and hydrogen production process was analyzed at the optimal condition. A significant interactive effect between glucose concentration and pH was observed, the optimal condition was initial pH 7.1, operation temperature 34.8 °C, glucose concentration 11.3 g/L and inoculation amount 10.4%. Hydrogen yield, maximum hydrogen production rate and hydrogen production potential were determined to be 1.29 mol H2/mol glucose, 86.7 L H2/L/h and 1.35 L H2/L. Metabolites analysis showed that E. faecium INET2 followed the pyruvate: formate lyase (Pfl) pathway in first 16 h, followed by the acetate-type fermentation and then shifted to butyrate-type fermentation. Maximum hydrogen production rate was accompanied with a quick formation of acetic acid.

    更新日期:2018-12-11
  • Modeling the development of hydrogen vapor cloud considering the presence of air humidity
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Yuanliang Liu, Jianjian Wei, Gang Lei, Tianxiang Wang, Yuqi Lan, Hong Chen, Tao Jin

    A three-dimensional CFD model for large-scale liquid hydrogen spills is developed and validated by the experiments carried out by NASA. The effect of humidity on the development of hydrogen vapor cloud is emphasized, with the modified expressions of Lee model accounting for the phase changes of water and hydrogen. The results show that the numerical prediction is more consistent with the experiment considering the presence of air humidity. The condensation of water in the atmosphere increases the buoyancy of the vapor cloud, and promotes the diffusion of the cloud in vertical direction. The dimension of the cloud in streamwise direction changes little under different humidity, due to the balance between the height-dependent wind speed and the induced buoyancy. The scope of visible cloud indicated by the condensed water vapor expands with the increasing air humidity, and still lies within the flammable domain when the relative humidity approaching to 75%. Water vapor condensation induces the cloud temperature rise under the same concentration, and the leeward part is more influenced compared with the upwind part.

    更新日期:2018-12-11
  • Nano composite composed of MoOx-La2O3Ni on SiO2 for storing hydrogen into CH4 via CO2 methanation
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Shuangshuang Li, Shaoxia Guo, Dandan Gong, Na Kang, Ke-Gong Fang, Yuan Liu

    The crucial problems for the catalysts of CO2 methanation are the low activity at low temperature and deactivation caused by metal sintering. In order to overcome the problems or to improve the shortages, a new scheme has been put forward by loading LaNi1-xMoxO3 with perovskite-type structure on SiO2. After reduction, Ni nanoparticles, MoOx and La2O3 would be all stay together and highly dispersed on SiO2 (Ni/MoOx-La2O3/SiO2). The techniques of BET, XRD, H2-TPR, HRTEM, ICP, H2 chemisorption and XPS were used to characterize the prepared samples. Through effectively combining MoOx which is active for the reaction of reverse water gas shift and Ni which can catalyze CO methanation, the resultant Ni/MoOx-La2O3/SiO2 catalyst exhibited pretty good performance for CO2 methanation, especially showing very good resistance to metal sintering. NiLa2O3/SiO2 catalyst without adding Mo was investigated for comparison. Since many metallic ions can enter into the lattice of a perovskite-type oxide, therefore, many combined catalysts for sequential reactions may be designed via this scheme.

    更新日期:2018-12-11
  • Electrochemical properties of Sr2.7-xCaxLn0.3Fe2-yCoyO7-δ cathode for intermediate-temperature solid oxide fuel cells
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Karinjilottu P. Padmasree, Ke-Yu Lai, Antonio F. Fuentes, Arumugam Manthiram

    The influence of Ca and Co doping in the Ruddlesden ‒ Popper series of oxide Sr2.7-xCaxLn0.3Fe2-yCoyO7-δ with x = 0 and 0.3, y = 0 and 0.6, and Ln = La and Nd on the electrical and thermal properties, catalytic activity for the oxygen reduction reaction (ORR) in solid oxide fuel cells (SOFC), and phase stability has been investigated. The Co-substituted samples display an increase in oxygen vacancies, electrical conductivity, thermal expansion coefficient, and electrocatalytic activity for both Ln = La and Nd. Although Ca doping in the Sr site slightly reduces the oxygen loss and thermal expansion coefficient, the symmetric cell performance is improved for both lanthanides at high temperatures. Among the cathode materials in this study, the highest catalytic activity for the ORR is achieved with Sr2.7Ca0.3Nd0.3Fe1.4Co0.6O7-δ + Gd0.2Ce0.8O1.9 (GDC) composite cathode with an area specific resistance of 0.034 Ω cm2 at 800 °C. Long-term thermal stability test shows that no impurity forms when Sr2.7-xCaxLn0.3Fe2-yCoyO7-δ oxides were heated at 800 °C for 150 h in air.

    更新日期:2018-12-11
  • Surface defect and rational design of TiO2−x nanobelts/ g-C3N4 nanosheets/ CdS quantum dots hierarchical structure for enhanced visible-light-driven photocatalysis
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Tianyu Zhao, Zipeng Xing, Ziyuan Xiu, Zhenzi Li, Shilin Yang, Qi Zhu, Wei Zhou

    TiO2-x/g-C3N4/CdS ternary heterojunctions are fabricated through thermal polymerization-chemical bath deposition combined with in-situ solid-state chemical reduction approach. The prepared materials are characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and X-ray photoelectron spectroscopy. The results show that the ternary heterojunctions are formed successfully and CdS quantum dots (QDs) and TiO2 are anchored on surface of g-C3N4 nanosheets simultaneously. The visible-light-driven photocatalytic degradation ratio of Bisphenol A and hydrogen production rate are up to 95% and ∼254.8 μmol h−1, respectively, which are several times higher than that of pristine TiO2. The excellent visible-light-driven photocatalytic activity can be ascribed to the synergistic effect of TiO2−x, g-C3N4 and CdS QDs which extend the photoresponse to visible light region and favor the spatial separation of photogenerated charge carriers.

    更新日期:2018-12-11
  • Enhancing under-rib mass transport in proton exchange membrane fuel cells using new serpentine flow field designs
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    F.B. Baz, Shinichi Ookawara, Mahmoud Ahmed

    New flow field configurations are developed to improve the performance of polymer electrolyte membrane fuel cells (PEMFCs). The developed designs aim to uniformly distribute the reactants over the reaction area of the catalyst layer surface, boost the under-rib convection mass transport through the gas diffusion layer, decrease the water flooding effect in the gas diffusion layer-catalyst layer interface, and maintain the membrane water content within the required range to augment protonic conductivity. To evaluate the performance parameters of a PEMFC, a comprehensive three-dimensional, two-phase mathematical model has been developed. The model includes the charge transport, electrochemical reactions, mass conservation, momentum, energy, and water transport equations. The results signify that the improved flow field patterns attain a considerable boosting of the output power, the under-rib convection mass transport, improvement of the reactant distribution over the catalyst layer surface and decline of the liquid water saturation in the gas diffusion layer-catalyst layer interface. The developed configurations achieve a higher power density of 0.82 W/cm2 at a current density of 1.74 A/cm2, compared to the standard serpentine configuration, which attains about 0.67 W/cm2 at a current density of 1.486 A/cm2.Accordingly, the develop configurations demonstrate a 22.6% enhancement in power density.

    更新日期:2018-12-11
  • Spinel CoFe2O4 supported by three dimensional graphene as high-performance bi-functional electrocatalysts for oxygen reduction and evolution reaction
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Tingwei Zhang, Zhongfang Li, Likai Wang, Zhixu Zhang, Suwen Wang

    Spinel CoFe2O4 supported on three dimensional graphene (3DG) is prepared by hydrothermal reaction, which is denoted as CoFe2O4/3DG. The 3DG is prepared by the templated method, where coal tar pitch (CTP) and MgO are used as the carbon source and the template, respectively. The microstructure and composition of the resultant have been investigated by X-ray diffraction as well as X-ray photoelectron spectroscopy indicating the formation of spinel CoFe2O4 and composite of CoFe2O4/3DG. The multilayer structure of 3DG and CoFe2O4/3DG is also examined by the Raman spectra. Electrochemically, CoFe2O4/3DG shows high-performance half-wave potential is 0.80 V vs. RHE in O2-saturated 0.1 M KOH, which is compared to 20 wt% Pt/C. When evaluated for OER activity, CoFe2O4/3DG obtains a low overpotential 1.63 V vs. RHE (at j = 10 mA cm−2), which is 180 mV better than 20 wt% Pt/C. Moreover, it possesses excellent durability superior to 20 wt% Pt/C.

    更新日期:2018-12-11
  • Enhancing the performance of photo-bioelectrochemical fuel cell using graphene oxide/cobalt/polypyrrole composite modified photo-biocathode in the presence of antibiotic
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Jian Sun, Wenjing Xu, Ping Yang, Nan Li, Yong Yuan, Hongguo Zhang, Xunan Ning, Yaping Zhang, Kenlin Chang, Yenping Peng, Kufan Chen

    Photo-bioelectrochemical fuel cell (PBFC) holds a great potential to harvest sustainable electrical energy from wastewater, but low power output limits its applications due to poor electrochemical performance of photo-biocathode. Additionally, antibiotics are ubiquitous in wastewater streams, but little is known regarding their effects on photo-biocathode performance of the PBFC. This study attempted to increase power output of PBFC through improvement of the photo-biocathode performance by modifying the biocathode with graphene oxide/cobalt/polypyrrole (GO/Co/PPy) composite in the presence of oxytetracycline. The GO/Co/PPy composite modified electrode fabricated by one-step electropolymerization method exhibited more excellent catalytic activity toward oxygen reduction compared to Co-alone and Co/PPy modified electrode. The PBFC with GO/Co/PPy composite modified biocathode produced a maximum power density of 19 mW/m2, which was almost 4-fold higher than that produced with the bare biocathode (4.9 mW/m2) due to improved bio-electrocatalytic performance of the bicathode by the GO/Co/PPy composite. The maximum power density of the PBFC was further increased 4.6 (105.5 mW/m2), 3.7 (88.7 mW/m2), 2.9 (74.6 mW/m2) and 1.9 (56 mW/m2) fold by exposure to 5, 10, 20, and 50 mg/L OTC, respectively. The further increases in power was due to reduced cathode's charge transfer resistance using degradation products of OTC as mediators and OTC-stimulated growth of species with extracellular electron transfer ability. However, the photosynthesis and growth of alga was negatively affected by OTC concentration higher than 10 mg/L, resulting performance deterioration of bicathode.

    更新日期:2018-12-11
  • Application of nanotechnology (nanoparticles) in dark fermentative hydrogen production
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Arivalagan Pugazhendhi, Sutha Shobana, Dinh Duc Nguyen, J. Rajesh Banu, Periyasamy Sivagurunathan, Soon Woong Chang, Vinoth Kumar Ponnusamy, Gopalakrishnan Kumar

    An enhanced dark fermentative hydrogen production via the introduction of nanotechnology, utilizing inorganic/organic nanoparticles (NPs) in the membrane of the bioreactors has been renowned these days. Such a nanotechnology includes metal and metal oxides like copper, gold, palladium, silver, iron-iron oxide, nickel-nickel oxide, silica, titanium oxide and carbon nanoparticles (CNTs) respectively have been revealed a noteworthy development in the dark fermentative hydrogen productivity. The pure/mixed cultures can generate dark fermentative hydrogen from biowastes feedstocks with pure sugars derived NPs and the efficiencies in the productivity depends on the nature and concentration of which the NPs employed. In this review, the prospective responsibilities of the inorganic/organic NPs in the enrichment of dark fermentative hydrogen production have been considered for the utilization of the feedstocks like sugars and biowastes materials. Additionally, certain commercial applications in supportive of the integrative approach of inorganic/organic NPs in the case of dark fermentative hydrogen productivity have been discussed.

    更新日期:2018-12-11
  • Syngas production by BFB gasification: Experimental comparison of different biomasses
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    Susanna Maisano, Francesco Urbani, Francesco Cipitì, Fabrizio Freni, Vitaliano Chiodo

    The potential use of waste feedstocks (beached Posidonia Oceanica and Citrus peels) as fuels for energy recovery by gasification process in a BFB reactor was explored. A direct comparison between two biomasses with a traditional woody biomass (White pine) was carried out through TG-DTG analysis and gasification experiments at 1023 K, 1 bar, Equivalence Ratio equal to 0.3, and different Steam to Biomass inlet ratio (0.5–1.0). Thermo-gravimetric measurements highlighted that under air-steam gasification conditions Posidonia Oceanica and Citrus peels decompose at temperatures lower than White pine due to the presence of high ash content (9–14 wt%) in the produced bio-chars. An increasing of syngas and H2 yields, increasing Steam to Biomass inlet stream, was obtained for all the biomasses investigated. Posidonia Oceanica gasification showed the best yield rates for both syngas (2.64 Nm3/kgbiomass) and hydrogen (0.65 Nm3/kgbiomass) at Steam to Biomass equal to 1 wt/wt, however it exhibited lower Cold Gas Efficiency, Carbon Conversion Efficiency and Lower Heating Value syngas values than Citrus peels gasification in all range of Steam to Biomass ratio.

    更新日期:2018-12-11
  • Hydrogen production from a model bio-oil/bio-glycerol mixture through steam reforming using Zeolite L supported catalysts
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    K. Bizkarra, V.L. Barrio, L. Gartzia-Rivero, J. Bañuelos, I. López-Arbeloa, J.F. Cambra

    Zeolite L featuring different size and shape (nanocrystals and discs), with and without alkaline metal exchange (Cs or Na), was used as catalyst support in bio-oil/bio-glycerol mixture Steam Reforming (SR). Zeolites were modified with CeO2 to improve support properties before the impregnation of nickel. Then, prepared catalysts were tested in SR of a multi-component synthetic bio-oil/bio-glycerol mixture at 1073 and 973 K, under atmospheric pressure and using a Steam to Carbon (S/C) ratio of 5.0. Activity tests showed that catalysts deactivated during the experiments at 973 K. In addition, the sodium exchange produced the sintering of the Zeolite L crystals. Thus, Na containing catalysts produced low conversions and hydrogen yields lower than 30%. On the other hand, Cs containing catalysts resulted in slightly lower hydrogen yields than the supports without this metallic cation. Regarding the morphology of the zeolites, the ones with disc shape were the most active for bio-oil SR purposes producing hydrogen yields close to 80% in the first reaction stage at 1073 K and hydrogen yields close to the 50% at the last reaction stage at 1073 K.

    更新日期:2018-12-11
  • Review: Enhancement of composite anode materials for low-temperature solid oxide fuels
    Int. J. Hydrogen Energy (IF 4.229) Pub Date : 2018-12-11
    K.H. Ng, H.A. Rahman, M.R. Somalu

    Solid oxide fuel cell (SOFC) technology is attractive for its high-energy efficiency and expanded fuel flexibility. It is also more environmentally benign than conventional power generation systems. Recently, increasing attention has been paid to intermediate-to-low-temperature solid oxide fuel cells, which operating at 400–800 °C. Reducing its operating temperature can render SOFC more competitive with other types of fuel cells and portable energy storage system (EES) over a range of applications (eg: transportation, portable, stationary) and more conducive for commercialization. The high-performance composite anode requirements for low operating temperature (400–600 °C) demand microstructural and chemical stability, high electronic conductivity, and good electrochemical performance. The current high-temperature anode, Ni-YSZ (nickel-yttria stabilized zirconia) is generally reported with high interfacial resistance at reduced temperatures. This review highlights several potential composite anode materials (Ni-based and Ni-free) that have been developed for low-temperature SOFCs within the past 10 years. This literature survey shows that most of these anodes still exhibit relatively high polarization resistance. Focus is also given on reducing polarization resistance to maintain the cell power density. In literature, common approaches that have been adopted to enhance the performance of anodes are (i) selecting high-performance electrolyte, (ii) exploiting nanopowder properties, and (iii) adding noble metals as electrocatalysts.

    更新日期:2018-12-11
  • Electrons stay hot
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10
    Giulia Tregnago

    Electrons stay hot Electrons stay hot, Published online: 10 December 2018; doi:10.1038/s41560-018-0303-0 Electrons stay hot

    更新日期:2018-12-11
  • Multi-site electrocatalysts for hydrogen evolution in neutral media by destabilization of water molecules
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10
    Cao-Thang Dinh, Ankit Jain, F. Pelayo García de Arquer, Phil De Luna, Jun Li, Ning Wang, Xueli Zheng, Jun Cai, Benjamin Z. Gregory, Oleksandr Voznyy, Bo Zhang, Min Liu, David Sinton, Ethan J. Crumlin, Edward H. Sargent

    High-performance hydrogen evolution reaction (HER) catalysts are compelling for the conversion of renewable electricity to fuels and feedstocks. The best HER catalysts rely on the use of platinum and show the highest performance in acidic media. Efficient HER catalysts based on inexpensive and Earth-abundant elements that operate in neutral (hence biocompatible) media could enable low-cost direct seawater splitting and the realization of bio-upgraded chemical fuels. In the challenging neutral-pH environment, water splitting is a multistep reaction. Here we present a HER catalyst comprising Ni and CrOx sites doped onto a Cu surface that operates efficiently in neutral media. The Ni and CrOx sites have strong binding energies for hydrogen and hydroxyl groups, respectively, which accelerates water dissociation, whereas the Cu has a weak hydrogen binding energy, promoting hydride coupling. The resulting catalyst exhibits a 48 mV overpotential at a current density of 10 mA cm−2 in a pH 7 buffer electrolyte. These findings suggest design principles for inexpensive, efficient and biocompatible catalytic systems.

    更新日期:2018-12-11
  • Super pseudocapacitors
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10
    Changjun Zhang

    Super pseudocapacitors Super pseudocapacitors, Published online: 10 December 2018; doi:10.1038/s41560-018-0301-2 Super pseudocapacitors

    更新日期:2018-12-11
  • Hydrophobic help
    Nat. Energy (IF 46.859) Pub Date : 2018-12-10
    James Gallagher

    Hydrophobic help Hydrophobic help, Published online: 10 December 2018; doi:10.1038/s41560-018-0304-z Hydrophobic help

    更新日期:2018-12-11
  • 更新日期:2018-12-11
  • Reduced Chemical Kinetic Mechanism for a Waste Cooking Oil Biodiesel/n-Pentanol Mixture for Internal Combustion Engine Simulation
    Energy Fuels (IF 3.024) Pub Date : 2018-12-10
    C. V. Manojkumar, Justin Jacob Thomas, V. R. Sabu, G. Nagarajan

    With increasing pollution concerns and stringent emission regulations, it has become difficult to meet the emission standards with the use of a single fuel. Binary and ternary fuel mixtures are being investigated all over the globe to satisfy the emission norms. In the present work, a reduced reaction mechanism for a waste cooking oil (WCO) biodiesel/n-pentanol mixture is proposed for the chemical kinetic simulation of an internal combustion engine. The mechanism consists of 146 species and 506 reactions. WCO biodiesel and n-pentanol are biofuels with many advantages. WCO biodiesel has properties (cetane number, viscosity, etc.) that are similar to those of diesel fuel, whereas n-pentanol has a high boiling temperature, low heat of vaporization, high lower heating value, and low autoignition temperature compared to other shorter chain alcohols. Mixing of higher molecular weight alcohols (n-pentanol) with diesel/biodiesel lowers the knock resistance as a result of their high reactivity at low as well as high temperatures. This characteristic makes them suitable for a diesel engine and advanced engine combustion modes, such as homogeneous charge compression ignition and reactivity controlled compression ignition engines.

    更新日期:2018-12-11
  • Removal of Organic Sulfur in Hydrocarbon Liquid Model Fuel by Ni-Loaded Carbon Prepared from Lignite
    Energy Fuels (IF 3.024) Pub Date : 2018-12-10
    Yuuki Mochizuki, Junpei Watanabe, Naoto Tsubouchi

    The removal of dibenzothiophene (DBT) in a hydrocarbon liquid model fuel (MF) by Ni-loaded carbon (Ni/C) prepared from lignite has been studied with a flow-type fixed-bed reactor. The performance of Ni/C in the removal of 500 ppmw S in MF depends on the amount of Ni loaded. The highest ability is observed at 11 wt % dry Ni under the conditions of a reduction time of 0.5 h and a desulfurization temperature of 200 °C. In addition, the reduction time influences the breakthrough curves, and it is found that the optimum condition for DBT removal from MF by Ni/C is 1.0 h. When the desulfurization temperature for evaluating the DBT removal ability of Ni/C is increased, the breakthrough and saturation points also increase, and the greatest performance is observed at 200 °C. From the identification of MF treated by Ni/C, it was found that a part of DBT in the MF feed is removed by chemical adsorption via cleavage of the C–S bond in the DBT molecule to form biphenyl which can adsorb onto a carbonaceous material surface.

    更新日期:2018-12-11
  • Mineralogical Composition Evolution and Thermogravimetric Characteristics of Sewage Sludge Ash at Different Ashing Temperatures
    Energy Fuels (IF 3.024) Pub Date : 2018-12-10
    Lin Mu, Chen Zhao, Liang Zhao, Bowen Chen, Zhiling Xu, Zhuqiang Yang, Yan Shang, Hongchao Yin
    更新日期:2018-12-11
  • Experiment and Modeling on Thermal Cracking of n-Dodecane at Supercritical Pressure
    Energy Fuels (IF 3.024) Pub Date : 2018-12-10
    Dingrui Zhang, Lingyun Hou, Mingyu Gao, Xiaoxiong Zhang

    A comprehensive understanding of the thermal cracking behavior of hydrocarbon fuels is important for thermal protection applications and investigations into the combustion of thermally cracked fuels. In the present study, n-dodecane is selected as a surrogate for aviation kerosene and it is subjected to a series of thermal cracking experiments at supercritical pressure. According to variations in chemical heat sink, fuel-conversion rate, and gas-production rate, the thermal cracking of n-dodecane is divided into three regions: primary, secondary, and severe. In the primary cracking region, the fuel-conversion rate is lower than 13%, and the liquid products contain only chain alkanes and alkenes. Owing to the mass fraction of main products being proportional to the fuel-conversion rate, a one-step global reaction kinetics is constructed. The secondary cracking region is characterized by rapidly increasing chemical heat sink, fuel-conversion rates, and gas-production rates with increasing fuel temperature, and the appearance of monocyclic aromatic hydrocarbons (MAHs) and cycloalkenes. A kinetic model containing three reactions is proposed for this region. This also considers the thermal decomposition of chain alkanes and alkenes, which result in the formation of MAHs and cycloalkenes. Severe cracking is observed for fuel-conversion rates above 71% where a rapid increase in the concentration of monocyclic and polycyclic aromatic hydrocarbons (PAHs) occurs. The increasing rate of chemical heat sink slows in this region which is characterized by the formation of MAHs, PAHs, and coke. A three-dimensional numerical model is built for the primary and secondary cracking regions, taking the effects of the flow, heat transfer, and thermal cracking of n-dodecane into consideration. Predicted values for the outlet temperature, fuel-conversion rate, and distribution of the main species in all tested cases agree well with the experimental results, validating the numerical model and kinetics for the primary and secondary thermal cracking of n-dodecane.

    更新日期:2018-12-11
  • A new method for direct determination of char yield during solid fuel pyrolysis in drop-tube furnace at high temperature and its comparison with ash tracer method
    Energy Fuels (IF 3.024) Pub Date : 2018-12-10
    Sui Boon Liaw, Hongwei Wu

    A drop tube furnace with novel double-tube configuration was successfully developed to directly determine char yields during the pyrolysis of a wide range of solid fuels (mallee wood, mallee leaf, rice husk, biosolid and subbituminous, bituminous and anthracite coal) at a gas temperature of 1573 K. The char yield from pyrolysis of mallee wood and mallee leaf is <5%, ~13% for rice husk, ~16% for biosolid, ~44% for subbituminous and bituminous coal and ~75% for anthracite coal. The retentions of Na, K, Mg and Ca in biomass chars are < 50%. About 35% of Na and K and ~66–85% of P and refractory species in biosolid are retained in the char. On the contrary, the retentions of major inorganic species in coal chars are >85%. This study shows using total ash as ash tracer results in 45–220% overestimation of char yields for biomass fuels and 13–27% for coals due to partial evaporation of ash. Similarly, selecting Na and K result in overestimation of biomass char yield by at least 2.5 times while P lead to overestimation of biomass char yields by at least 80%, due to substantial release of these species during pyrolysis. Similarly, selecting Mg, Ca, Al, Fe, Ti and Si as tracer also result in inaccurate estimation of char yields due to partial release of these elements during pyrolysis. It is noted that for Si, which is often used as a tracer, the overestimation of char yields is 9-16% for coals but can be substantial (17-50%) for the case of biomass samples due to the substantial Si release during the pyrolysis of biomass (especially mallee wood with ~32% of Si released). Clearly, for the solid fuels studied, no single element can be reliably used as tracer for calculating char yield during pyrolysis at high temperature. The new experimental method developed in this study fill this critical gaps and enables directly determination of char yield during solid fuel pyrolysis in drop-tube furnace at high temperature.

    更新日期:2018-12-11
  • EFFECT OF REACTOR CONFIGURATION ON THE HYDROTREATING OF ATMOSPHERIC RESIDUE
    Energy Fuels (IF 3.024) Pub Date : 2018-12-10
    Fernando Alonso, Jorge Ancheyta, Guillermo Centeno, Gustavo Marroquin, REBECA SILVA RODRIGO

    To study the effect of reactor configuration on hydrotreating, a series of experiments was carried out in a pilot plant equipped with two reactors in series that can operate in two modes: fixed-bed reactor (FBR) or ebullated-bed reactor (EBR). The experiments were carried out with atmospheric residue as feedstock and commercial catalysts at pressure of 100 kg/cm2 and temperature of 380°C and 400°C. The highest conversions were obtained for the EBR-EBR (35.67-52.21%), and EBR-FBR (29.08-53.09%) configurations, unlike FBR-FBR configuration that exhibited lowest conversion (15.42-27.34%). At 400°C the EBR-FBR and FBR-FBR configurations showed higher hydrodemetalization (HDM) than the others (81.00% and 76.95%, respectively). It was confirmed that the formation of sediments increases at high temperatures, where at 400°C it begins to be significant for the EBR-FBR and EBR-EBR configurations (0.010-0.767 wt.% and 0.041-0.613 wt.%, respectively), in contrast to the FBR-FBR configuration that presented lesser formation of sediments (0.003-0.009 wt.%).

    更新日期:2018-12-11
  • C(sp3)–H Bond Activation by Perovskite Solar Photocatalyst Cell
    ACS Energy Lett. (IF 12.277) Pub Date : 2018-12-10
    Haowei Huang, Haifeng Yuan, Jiwu Zhao, Guillermo Solís-Fernández, Chen Zhou, Jin Won Seo, Jelle Hendrix, Elke Debroye, Julian A. Steele, Johan Hofkens, Jinlin Long, Maarten B. J. Roeffaers
    更新日期:2018-12-11
  • Anion Effects on Cathode Electrochemical Activity in Rechargeable Magnesium Batteries: A Case Study of V2O5
    ACS Energy Lett. (IF 12.277) Pub Date : 2018-12-10
    Ran Attias, Michael Salama, Baruch Hirsch, Reeta Pant, Yosef Gofer, Doron Aurbach
    更新日期:2018-12-11
  • Reducing Surface Recombination Velocities at the Electrical Contacts Will Improve Perovskite Photovoltaics
    ACS Energy Lett. (IF 12.277) Pub Date : 2018-12-10
    Jian Wang, Weifei Fu, Sarthak Jariwala, Irika Sinha, Alex K.-Y. Jen, David S Ginger

    We explore the effects of non-radiative recombination at the extracting contacts on the achievable performance of halide perovskite photovoltaic cells. First, we perform device simulations using standard drift-diffusion models with experimental semiconductor parameters matching those of methylammonium lead triiodide (MAPbI3). We quantify the range of surface recombination velocities (SRVs) that would allow this archetypal perovskite to reach power conversion efficiencies of 27%. In particular, for contacts with well-aligned energy levels, SRVs of ~1-10 cm/sec should enable open circuit voltages of 1.30V, within 96% of the Shockley-Quiesser limit. Next, we use time-resolved photoluminescence to experimentally determine the SRVs on 14 different common electron- and hole-extracting contacts, including TiO2, SnO2, ZnO, PCBM, ITIC, ICBA, TPBi, PEDOT:PSS, PTAA, PVK, NiO, MoO3, WO3, and spiro-OMeTAD. These results point the way to the selection and rational engineering of better contacts as a means to achieve higher efficiencies in perovskite solar cells.

    更新日期:2018-12-11
  • Tellurium-based Double Perovskites A2TeX6 with Tunable Bandgap and Long Carrier Diffusion Length for Optoelectronic Applications
    ACS Energy Lett. (IF 12.277) Pub Date : 2018-12-10
    Dianxing Ju, Xiaopeng Zheng, Jun Yin, Zhiwen Qiu, Bekir Turedi, Xiaolong Liu, Yangyang Dang, Bingqiang Cao, Omar F. Mohammed, Osman M. Bakr, Xutang Tao

    Lead-free hybrid perovskites have attracted immense interest as environmentally friendly light absorbers. Here, we report on tellurium (Te)-based double perovskites A2TeX6 (A= MA, FA or BA, X = Br- or I-, MA= CH3NH3, FA= CH(NH2)2, BA= benzylamine) as potentially active materials for optoelectronic devices. This perovskites exhibit a tunable bandgap (1.42 eV-2.02 eV), a low trap density (~1010 cm-3), and a high mobility (~ 65 cm2 V-1 s-1). Encouragingly, the MA2TeBr6 single crystal with a bandgap of 2.00 eV possesses a long carrier lifetime of ~6 μs and corresponding carrier diffusion lengths of ~38 μm, which are ideal characteristics for a material for photodetectors and tandem solar cells. Moreover, A2TeX6 perovskites are relatively robust in ambient conditions, being stable for at least two months without showing any signs of phase change. Our findings bring to the forefront a family of lead-free Te-based perovskites for non-toxic perovskite optoelectronics.

    更新日期:2018-12-11
  • Operation Mechanism of Perovskite Quantum Dot Solar Cells Probed by Impedance Spectroscopy
    ACS Energy Lett. (IF 12.277) Pub Date : 2018-12-10
    Zahra Zolfaghari, Ehsan Hassanabadi, Didac Pitarch-Tena, Seog Joon Yoon, Zahra Shariatinia, Jao van de Lagemaat, Joseph M. Luther, Ivan Mora-Seró

    We fabricated perovskite quantum dot solar cells (PQDSCs) varying the thickness of the QD layer by controlling the number of deposition cycles, that were systematically with impedance spectroscopy. Despite the evident structural differences with respect to standard perovskite solar cells (PSCs), similar impedance spectra were obtained for PQDSCs, pointing to similar working principles in terms of the active layer. We distinguish two different regimes: at low illumination, recombination is ruled by multiple trapping with trap distributions and/or shunting. However, at higher light intensities Shockley-Read-Hall recombination is observed. In addition, the low frequency capacitance, CLF, of PQDSCs increases several orders of magnitude by varying the illumination from dark to 1-sun conditions. This feature has not been observed in other kinds of photovoltaic devices and is characteristic of PSCs. Despite no consensus about the exact mechanism responsible for CLF the suggested models point to an ion migration origin. Its observation in thin film and PQDSCs devices implies a similar effect in both.

    更新日期:2018-12-11
  • Dyadic promotion of photocatalytic aerobic oxidation via the Mott-Schottky effect enabled by nitrogen-doped carbon from imidazolium-based ionic polymer
    Energy Environ. Sci. (IF 30.067) Pub Date : 2018-12-11
    Hong Zhong, Can Yang, Lizhou Fan, Zhi-hua Fu, Xue Yang, Xinchen Wang, Ruihu Wang

    Metal/semiconductor systems are one type of promising heterogeneous photocatalysts for solar conversion. The injection of hot electrons from photoactivated metals to semiconductors is a rate-determining step owing to Schottky barrier created at the interface. It is highly desirable to develop new approaches for promoting hot electron transfer. Herein, we present one type of new Mott-Schottky-type photocatalytic materials consisting of TiO2 nanosheets and Ru nanoparticles (NPs) encapsulated by nitrogen-doped carbon (TiO2@NC-Ru-T). They are readily available through the conformal encapsulation of TiO2 by main-chain imidazolium-based ionic polymer (ImIP), followed by anion exchange with perruthenate and subsequent pyrolysis, the sintering of Ru NPs is effectively inhibited by ImIP, generating small-size and well-dispersed Ru NPs. The nitrogen-doped carbon in TiO2@NC-Ru-T both strengthens the performance of Ru NPs and facilitates photoelectron transfer from photoactivated Ru NPs to TiO2 through Mott-Schottky contact. The dyadic effects greatly promote selective aerobic oxidation of alcohols with air as an oxidant under visible light irradiation. This work provides a feasible protocol for improving visible light absorption and charge/electron transfer in the photocatalytic reactions, and holds great promises for developing new type of soalr-to-chemical energy conversion reactions

    更新日期:2018-12-11
  • The nature of active centers catalyzing oxygen electro-reduction at platinum surfaces in alkaline media
    Energy Environ. Sci. (IF 30.067) Pub Date : 2018-12-04
    Yunchang Liang, David McLaughlin, Christoph Csoklich, Oliver Schneider, Aliaksandr S. Bandarenka
    更新日期:2018-12-11
  • A Manganese Hydride Molecular Sieve for Practical Hydrogen Storage under Ambient Conditions
    Energy Environ. Sci. (IF 30.067) Pub Date : 2018-12-10
    David M Antonelli, Michel Trudeau, Nikolas Kaltsoyannis, Juergen Eckert, Jan Peter Peter Embs, Leah Morris, James Hales, Peter Georgiev

    A viable hydrogen economy has thus far been hampered by the lack of an inexpensive and convenient hydrogen storage solution meeting all requirements, especially in the areas of long hauls and delivery infrastructure. Current approaches require high pressure and/or complex heat management systems to achieve acceptable storage densities. Herein we present a manganese hydride molecular sieve that can be readily synthesized from inexpensive precursors and demonstrates a reversible excess adsorption performance of 10.5 wt% and 197 kgH2m-3 at 120 bar at ambient temperature with no loss of activity after 54 cycles. Inelastic neutron scattering and computational studies confirm Kubas binding as the principal mechanism. The thermodynamically neutral adsorption process allows for a simple system without the need for heat management using moderate pressure as a toggle. A storage material with these properties will allow the DOE system targets for storage and delivery to be achieved, providing a practical alternative to incumbents such 700 bar systems, which generally provide volumetric storage values of 40 kgH2m-3 or less, while retaining advantages over batteries such as fill time and energy density. Reasonable estimates for production costs and loss of performance due to system implementation project total energy storage costs roughly 5 times cheaper than those for 700 bar tanks, potentially opening doors for increased adoption of hydrogen as an energy vector.

    更新日期:2018-12-11
  • Mixed phononic and non-phononic transport in hybrid lead halide perovskites: glass-crystal duality, dynamical disorder, and anharmonicity
    Energy Environ. Sci. (IF 30.067) Pub Date : 2018-12-10
    Taishan Zhu, Elif Ertekin

    In hybrid materials, a high-symmetry lattice is decorated by low-symmetry building blocks. The result is an aperiodic solid that hosts many nearly-degenerate disordered configurations. Using the perovskite methylammonium lead iodide (MAPbI3) as a prototype hybrid material, we show that the inherent disorder renders the conventional phonon picture of transport insufficient. Ab-initio molecular dynamics and analysis of the spectral energy density reveal that vibrational carriers simultaneously exhibit features of both classical phonons and of carriers typically found in glasses. The low frequency modes retain elements of acoustic waves but exhibit extremely short lifetimes of only a few tens of picoseconds. For higher frequency modes, strong scattering due to rapid motion and reconfiguration of the organic cation molecules induces a loss of definition of the wave vector. Lattice dynamics shows that these carriers are more akin to diffusons -- the nonwave carriers in vitreous materials -- and are the dominant contributors to thermal conduction near room temperature. To unify the framework of glassy diffusons with that of phonons scattered at the ultimate limit, three-phonon interactions resolved from first-principles expose anharmonic effects two orders of magnitude higher than in silicon. The dominant anharmonic interactions occur within modes of the PbI6 octahedral framework itself, as well as between modes of the octahedral framework and modes localized to the MA molecules. The former arises from long-range interactions due to resonant bonding, and the latter from polar rotor scattering of the MA molecules. This establishes a clear microscopic connection between symmetry-breaking, dynamical disorder, anharmonicity, and the loss of wave nature in MAPbI3.

    更新日期:2018-12-11
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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