A 2D/1D TiO2 nanosheet/CdS nanorods heterostructure with enhanced photocatalytic water splitting performance for H2 evolution Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Junmei Wang, Zhijian Wang, Peng Qu, Qinchao Xu, Jianfeng Zheng, Suping Jia, Jiazang Chen, Zhenping Zhu
TiO2 with exposed (001) facets were composited with CdS nanorods to construct 2D/1D heterojunction. As comparison, P25 with mainly exposed (101) facets were employed to combine with CdS nanorods. The 2D/1D heterojunction of TiO2 nanosheets and CdS nanorod displayed 3.7 times higher hydrogen generation than that of P25/CdS composites. The results indicated that TiO2 with exposed (001) facets were favorable for enhancing the photocatalytic activity of CdS via optimizing the heterojunction between TiO2 and CdS. Photoluminescence and photoelectrochemical characteristics results demonstrated that the 2D-TiO2/1D-CdS heterojunction exhibits higher separation efficiency of photoinduced carriers and superior electron transfer ability. This work exemplifies that heterojunction modification is an effective strategy to improve the efficiency of the photocatalyst composites.
Stable SrCo0.7Fe0.2Zr0.1O3-δ cathode material for proton conducting solid oxide fuel cell reactors Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Lin Shao, Fengzhan Si, Xian-Zhu Fu, Jing-Li Luo
SrCo0.7Fe0.2Zr0.1O3-δ (SCFZ) perovskite is prepared using a combustion method. SCFZ exhibits high stability while SrCo0.8Fe0.2O3-δ without Zr doping decomposes in CO2 and H2O- containing atmosphere at elevated temperature. SCFZ also displays excellent chemical compatibility with BaCe0.7Y0.2Zr0.1O3-δ (BCYZ) proton conductor. A ceramic membrane fuel cell reactor is assembled with SCFZ + BCYZ composite cathode, porous Pt anode and BCYZ electrolyte. High selective ethylene and electrical energy are co-generated from ethane in the proton conducting solid oxide fuel cell reactor.
Catalytic dehydrogenation study of dodecahydro-N-ethylcarbazole by noble metal supported on reduced graphene oxide Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Bin Wang, Tie-yan Chang, Zhao Jiang, Jin-jia Wei, Yong-hai Zhang, Sen Yang, Tao Fang
Electrooxidation study of pure ethanol/methanol and their mixture for the application in direct alcohol alkaline fuel cells (DAAFCs) Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Uday Kumar Gupta, Hiralal Pramanik
Aliphatic alcohol mainly, ethanol, methanol and their mixture were subjected to electrooxidation study using cyclic voltammetry (CV) technique in a three electrodes half cell assembly (PGSTAT204, Autolab Netherlands). A single cell set up of direct alcohol alkaline fuel cell (DAAFC) was fabricated using laboratory synthesized alkaline membrane to validate the CV results. The DAAFC conditions were kept similar as that of CV experiments. The anode and cathode electrocatalysts were Pt-Ru (30%:15% by wt.)/Carbon black (C) (Alfa Aesar, USA) and Pt (40% by wt.)/High Surface Area Carbon (CHSA) (Alfa Aesar, USA) respectively. The CV and single cell experiments were performed at a temperature of 30 °C. The anode electrocatalyst was in the range of 0.5 mg/cm2 to 1.5 mg/cm2 for half cell CV analysis. The cell voltage and current density data were recorded for different concentrations of fuel (ethanol or methanol) and their mixture mixed with different concentration of KOH as electrolyte. The optimum electrocatalyst loading in half cell study was found to be 1 mg/cm2 of Pt-Ru/C irrespective of fuel used. The single cell was tested using optimum anode loading of 1 mg/cm2 of Pt-Ru/C which was found in CV experiment. Cathode loading was kept similar, in the order of 1 mg/cm2 Pt/CHSA. In single cell experiment, the maximum open circuit voltage (OCV) of 0.75 V and power density of 3.57 mW/cm2 at a current density of 17.76 mA/cm2 were obtained for the fuel of 2 M ethanol mixed with 1 M KOH. Whereas, maximum OCV of 0.62 V and power density of 7.10 mW/cm2 at a current density of 23.53 mA/cm2 were obtained for the fuel of 3 M methanol mixed with 6 M KOH. The mixture of methanol and ethanol (1:3) mixed with 0.5 M KOH produced the maximum OCV of 0.66 V and power density of 1.98 mW/cm2 at a current density of 11.54 mA/cm2.
Ultrashort-pulse laser structured titanium surfaces with sputter-coated platinum catalyst as hydrogen evolution electrodes for alkaline water electrolysis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Andreas Gabler, Christian I. Müller, Thomas Rauscher, Thomas Gimpel, Robert Hahn, Michael Köhring, Bernd Kieback, Lars Röntzsch, Wolfgang Schade
For the first time, we report on micro- and nanostructured Ti surfaces produced by ultrashort-pulse laser processing followed by sputter deposition of Pt aiming at efficient cathode electrodes for alkaline water electrolysis. We studied the laser processing-induced surface morphology, the elemental composition of the surface, the specific surface increase, the wetting behavior as well as the activity of the hydrogen evolution reaction. It is demonstrated that ultrashort-pulse laser structuring in combination with thin layer catalyst deposition can dramatically boost the performance of cathodes for the hydrogen evolution reaction due to the enormous increase in specific surface in combination with superhydrophilic and superwetting properties leading to a rapid gas bubble detachment.
Multiwalled Carbon Nanotubes anode with low oxygen content for ascorbic acid fuel cells design Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Andrés A. Arrocha-Arcos, M. Miranda-Hernández
A new catalyst of AlCu@ZnO for hydrogen evolution reaction Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Bulut Hüner, Murat Farsak, Esra Telli
Thin films of undoped ZnO, Al-doped ZnO, Cu-doped ZnO, and AlCu@ZnO deposited on indium tin oxide were performed by the sol-gel spin coating method. The prepared ZnO thin films were investigated for their structural and electrical properties after annealing at 500 °C for 1 h. ZnO thin films were characterized by electrochemical impedance spectroscopy, linear sweep voltammetry, scanning electron microscopy, Fourier transform infrared spectroscopy and Mott Schottky. According to the results obtained from the Nyquist diagrams of the ZnO thin films, the resistance value was found to decrease with binary doping and the resistance value was found to be lowest in AlCu@ZnO doped thin film containing 0.01 M Al and 0.1 M Cu. As ZnO thin films go to cathodic potentials, it is seen that the cathodic current value of ZnO with undoped is the lowest. It has been found that only Al and Cu doping showed less cathodic current than double doping.
Dilution of hazardous vapor cloud in liquid hydrogen spill process under different source conditions Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Yuanliang Liu, Jianjian Wei, Gang Lei, Yuqi Lan, Hong Chen, Tao Jin
Dilution of hydrogen vapor cloud formed by the liquid hydrogen spills under different spill amounts, spill rates and liquid mass fractions at the exit were numerically investigated. Three dimensional CFD simulations were performed with ANSYS FLUENT using Realizable k-ε turbulence model. Time variation of the maximum hydrogen concentration (t = 0 s at the end of the spill) is most sensitive to the liquid mass fraction, followed by the spill rate, and finally the spill amount. The dilution process is nearly unaffected by the spill amount. With the increment of spill rates, the dilution speed first decreases and then remains approximately unchanged, which can be attributed to the combined effects of the gaseous hydrogen generated per unit time and the source disturbances generated by the spill and evaporation process. In addition, the dilution accelerates with the increment of liquid mass fraction at the exit. The turbulence induced by the evaporation of liquid hydrogen promotes the mixing and dilution processes, while the temperature drop in the ground and the ambient air due to liquid evaporation has little influence on the overall dilution of the vapor cloud. The durations of detonation and flammability when the liquid mass fraction is 0% are 1.65 and 1.88 times of those when liquid mass fraction is 100%, respectively.
Zn-doped hematite modified by graphene-like WS2: A p-type semiconductor hybrid photocathode for water splitting to produce hydrogen Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Dongmei Chu, Kezhen Li, Aijuan Liu, Jie Huang, Chunyong Zhang, Ping Yang, Yukou Du, Cheng Lu
A p-type Zn-doped hematite (α-Fe2O3(Zn)) in spindle-shape with an acceptor density of ca. 4.21 × 1018 cm−3 were synthesized by a facile hydrothermal method. After α-Fe2O3(Zn) was modified with graphene-like WS2 (α-Fe2O3(Zn)/WS2), the photoelectrochemical performances of the composite can be further enhanced. A photocell composed of the p-type α-Fe2O3(Zn)/WS2 nanocomposite as photocathode and n-type α-Fe2O3 as photoanode was assembled to estimate the photocatalytic activity of α-Fe2O3(Zn)/WS2. The amount of the hydrogen and oxygen produced from this tandem cell with the optimal electrodes under 2 h simulated solar light irradiation is 12.5 μmol and 4.3 μmol, respectively.
Highly active screen-printed Ir Ti4O7 anodes for proton exchange membrane electrolyzers Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Tiago Lagarteira, Feng Han, Tobias Morawietz, Renate Hiesgen, Daniel Garcia Sanchez, Adélio Mendes, Aldo Gago, Rémi Costa
Electroceramic support materials can help reducing the noble-metal loading of iridium in the membrane electrodes assembly (MEA) of proton exchange membrane (PEM) electrolyzers. Highly active anodes containing Ir-black catalyst and submicronic Ti4O7 are manufactured through screen printing technique. Several vehicle solvents, including ethane-1,2-diol; propane-1,2-diol and cyclohexanol are investigated. Suitable functional anodic layer with iridium loading as low as 0.4 mg cm−2 is obtained. Surface properties of the deposited layers are investigated by atomic force microscopy (AFM). The most homogeneous coating with the highest electronic conductivity is obtained using cyclohexanol. Tests in PEM electrolyzer operating at 1.7 V and 40 °C demonstrate that the CCM with anode coated with cyclohexanol presents a 1.5-fold higher Ir-mass activity than that of the commercial CCM.
Study on combustion and emission characteristics of a n-butanol engine with hydrogen direct injection under lean burn conditions Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Fanbo Meng, Xiumin Yu, Ling He, Yahui Liu, Ye Wang
The n-butanol fuel, as a renewable and clean biofuel, could ease the energy crisis and decrease the harmful emissions. As another clean and renewable energy, hydrogen properly offset the high HC emissions and the insufficient of dynamic property of pure n-butanol fuel in SI engines, because of the high diffusion coefficient, high adiabatic flame velocity and low heat value. Hydrogen direct injection not only avoids backfire and lower intake efficiency but also promotes to form in-cylinder stratified mixture, which is helpful to enhance combustion and reduce emissions. This experimental study focused on the combustion and emissions characteristics of a hydrogen direct injection stratified n-butanol engine. Three different hydrogen addition fractions (0%, 2.5%, 5%) were used under five different spark timing (10° ,15° ,20° ,25° ,30° CA BTDC). Engine speed and excess air ratio stabled at 1500 rpm and 1.2 respectively. The direct injection timing of the hydrogen was optimized to form a beter stratified mixture. The obtained results demonstrated that brake power and brake thermal efficiency are increased by addition hydrogen directly injected. The BSFC is decreased with the addition of hydrogen. The peak cylinder pressure and the instantaneous heat release rate raises with the increase of the hydrogen addition fraction. In addition, the HC and CO emissions drop while the NOx emissions sharply rise with the addition of hydrogen. As a whole, with hydrogen direct injection, the power and fuel economy performance of n-butanol engine are markedly improved, harmful emissions are partly decreased.
Numerical investigation on combustion characteristics of methane/air in a micro-combustor with a regular triangular pyramid bluff body Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 Yunfei Yan, Hongyu Yan, Li Zhang, Lixian Li, Junchen Zhu, Zhien Zhang
Combustion characteristics of methane/air in a micro-combustor with a regular triangular pyramid bluff body were numerically investigated. Results reveal that the blow-off limit of the micro-combustor with a regular triangular pyramid bluff body is 2.4 times of that in the micro-combustor without bluff body. With the increase of inlet velocity, the recirculation zone expands and preferential transport effect behind the bluff body is intensified. Therefore, the local equivalence ratio in the recirculation zone increases when Φ = 0.8, but the growth trend of local equivalence ratio is not obvious when the inlet velocity exceeds 10 m/s. When Φ < 1.0, adding small amount of hydrogen into gas mixture can speed up the significant elementary reaction, leading to an increase of methane conversion. It's found that both the methane conversion rate and the temperature behind the bluff body reaches the highest when blockage ratio increase to 0.22.
Thermal desorption spectrometer for measuring ppm concentrations of trapped hydrogen Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-22 C.V. Tapia-Bastidas, A. Atrens, E. MacA. Gray
This paper describes an ultra-high-vacuum thermal desorption spectrometer, designed to study hydrogen in steels at ∼1 wt ppm (∼50 atomic ppm) concentration. The high sensitivity achieved also facilitates the analysis of surface phenomena. The instrument was evaluated with model materials and provided good measurements of diffusible hydrogen. A hydrogen peak at ∼350 °C was identified for steels exposed to water during hydrogen charging, and attributed to water molecules adsorbed on the sample surface for samples exposed to the laboratory atmosphere for times as short as 1 min. Recommendations are made for precautions to be taken when handling the samples.
Hydrogen production by water-gas shift reaction over Co-promoted MoS2/Al2O3 catalyst: The intrinsic activities of Co-promoted and unprompted sites Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 Jianjun Chen, Jincheng Zhang, Jinxing Mi, Elizabeth Dominguez Garcia, Yanning Cao, Lilong Jiang, Laetitia Oliviero, Françoise Maugé
Co-promoted MoS2/Al2O3 is the industrial-widely used catalyst for hydrogen production by water-gas shift (WGS) reaction under sulfur-containing condition. Despite of the intensive physicochemical characterizations, the intrinsic activities of Co-promoted and unprompted sites on this catalyst are still unreported, mainly owning to the lack of quantification method of catalytic sulfide sites. With low temperature CO adsorption followed by IR spectroscopy, a distinguish technique developed by our group, this short communication reports the temperature-dependent TOFs (turnover frequencies) of these two sites, and reveals that Co-promoted site is intrinsically much more active than unprompted site at low temperatures, while these two sites are catalytically comparable at higher reaction temperatures. The catalytically different performances are related to the different apparent activation energies of WGS reaction on these two sites. This work fills in the long-standing gaps in hydrogen production by WGS reaction over sulfided CoMo/Al2O3 catalyst.
Power quality enhancement of grid connected fuel cell using evolutionary computing techniques Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 Mohamed I. Mosaad, H.S. Ramadan
Fuel Cell (FC), as a type of new renewable energy sources grid-connected at Point of Common Coupling (PCC), is introduced in this study. This article presents the power quality improvement of the FC integrated to the power network through a chopper and an inverter using the conventional PI controller. Two PI controllers, tuned by three recent different evolutionary computing techniques namely Harmony Search (HS), Modified Flower Pollination Algorithm (MFPA) and Electromagnetic Field Optimization (EFO) methods are considered. The two PI controllers are used for driving the inverter connected the on-grid FC in order to govern the PCC voltage between the FC and the power network. These two controllers are exploited to drive the power and the current regulators at different voltage sag and swell conditions. The three optimization methods are compared to the Particle Swarm Optimization (PSO) with regards to voltage profile, powr quality and execution time. Simulation results, using Matlab/Simulink™, show the significance of the three optimization techniques in regulating the voltage at PCC with reduced harmonics during the system voltage sag and swell conditions when compared to the PSO. Through the numerical analysis, the superiority of MFPA method among the different optimization metaheuristic techniques is highlighted particularly for enhanced dynamic voltage response purposes.
Syngas production from dry methane reforming over yttrium-promoted nickel-KIT-6 catalysts Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 Katarzyna Świrk, Maria Elena Gálvez, Monika Motak, Teresa Grzybek, Magnus Rønning, Patrick Da Costa
Dry reforming of methane was studied over Ni,Y-promoted KIT-6 ordered mesoporous silicas, prepared by incipient impregnation (nickel content 12 wt%, yttrium content of 4 wt%, 8 wt% or 12 wt%). The catalysts were characterized by XRF, FT-IR, TGA/DSC-MS, N2-adsorption, TEM, HRTEM, XRD and TPR-H2. The promotion with 8 wt% Y (Y/Si = 0.05) resulted in the highest activity and H2/CO molar ratio closer to the stoichiometric value at temperatures from 600 to 750 °C. The characterization results of the yttrium promoted materials showed higher reducibility of the bulk NiO, bigger Ni crystallite size after reduction and DRM test, and better dispersion of nickel in the channels of the KIT-6 support. Additionally, larger Ni particles were observed on the external surface of the support, which may be related to catalytic selectivity towards carbon forming reactions. Upon dry methane reforming the segregated phases of Niº, Y2O3, and possibly Y2Si2O7 were registered. No presence of a Ni,Y alloy was observed.
Bismuth doped TiO2 as an excellent photocathode catalyst to enhance the performance of microbial fuel cell Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 G.D. Bhowmick, Md.T. Noori, Indrasis Das, B. Neethu, M.M. Ghangrekar, A. Mitra
Bismuth impregnation on pure TiO2 (Bi TiO2) was carried out and tested in microbial fuel cell (MFC) as photocathode catalyst. UV–Visible spectral observation confirmed higher catalytic activity of Bi TiO2 under visible light irradiation with reduced band gap of 2.80 eV as compared to pure TiO2 (3.26 eV). Electrochemical impedance spectroscopy also showed two times higher exchange current density with lower charge transfer resistance for Bi TiO2 (1.90 Ω) than pure TiO2 (3.95 Ω), thus confirming it as superior oxygen reduction reaction catalyst. MFC operated with Bi TiO2 could generate a maximum power density of 224 mW m−2, which was higher than MFC with Pt as cathode catalyst (194 mW m−2) and much higher than MFCs with TiO2 catalyzed cathode (68 mW m−2) and without any cathode catalyst (60 mW m−2). The results thus promote Bi doped TiO2 as a superior low-cost alternative to the costly Pt catalyst to take this MFC technology forward for field application.
Hydrogen-fueled detonation ramjet model: Wind tunnel tests at approach air stream Mach number 5.7 and stagnation temperature 1500 K Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 S.M. Frolov, V.I. Zvegintsev, V.S. Ivanov, V.S. Aksenov, I.O. Shamshin, D.A. Vnuchkov, D.G. Nalivaichenko, A.A. Berlin, V.M. Fomin, A.N. Shiplyuk, N.N. Yakovlev
The mode of continuous spinning detonation (CSD) combustion of hydrogen in the annular combustor of a model of a hydrogen-fueled detonation ramjet under conditions of approach air stream Mach number 5.7 and stagnation temperature 1500 K is registered experimentally in a short-duration (pulsed) wind tunnel at the overall air-to-hydrogen equivalence ratio (ER) ranging from 0.7 to 1.4. The maximum values of thrust and specific impulse of the ramjet model are attained at ER = 1.25 and are estimated as 1550 N and 3300 s, respectively. At 1.4 < ER < 1.6, the mode of longitudinally pulsating detonation (LPD) combustion is registered with somewhat lower values of thrust and specific impulse.
Improvement in the durability of carbon black-supported Pt cathode catalysts by silica-coating for use in PEFCs Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 Sakae Takenaka, Masaki Goto, Yasuyuki Masuda, Shoichiro Emura, Masahiro Kishida
Commercially available Pt metal catalysts supported on carbon black (Pt/CB) for polymer electrolyte fuel cell (PEFC) cathodes were covered with silica layers to improve their durability under the severe cathode operating conditions. The Pt metal particles in the Pt/CB catalyst grew in size during the accelerated durability tests (potential cycling between 0.6 and 1.0 V vs. RHE in an aqueous HClO4 electrolyte). Thus, the Pt/CB catalyst was seriously deactivated for the oxygen reduction reaction over the course of the durability tests. In contrast, the silica layers, which wrapped around the Pt metal particles in the silica-coated Pt/CB catalyst, prevented the migration of the Pt metal particles on the carbon supports and the diffusion of Pt cations out of the silica layers. Thus, the silica-coated Pt/CB catalysts maintained a high activity for the oxygen reduction reaction over the course of the durability tests. In addition, the silica-coated Pt/CB prepared from methyltriethoxysilane showed a higher activity than that prepared from tetraethoxysilane. The porous structures and hydrophobicity of silica prepared from methyltriethoxysilane promoted the diffusion of oxygen and water molecules in the silica layers of the silica-coated Pt catalysts.
Effect of hydrogen supplementation on engine performance and emissions Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-21 Priybrat Sharma, Atul Dhar
Vehicular Pollution and environmental degradation are on the rise with increasing vehicles and to stop this strict regulation have been put on vehicular emissions. Also, the depleting fossil fuels are of great concern for energy security. This has motivated the researchers to invest considerable resources in finding cleaner burning, sustainable and renewable fuels. However renewable fuels independently are not sufficient to deal with the problem at hand due to supply constraints. Hence, advanced combustion technologies such as homogeneous charge compression ignition (HCCI), low-temperature combustion (LTC), and dual fuel engines are extensively researched upon. In this context, this work investigates dual fuel mode combustion using a constant speed diesel engine, operated using hydrogen and diesel. The engine is operated at 25, 50 and 75% loads and substitution of diesel energy with hydrogen energy is done as 0, 5, 10 and 20%. The effect of hydrogen energy share (HES) enhancement on engine performance and emissions is investigated. In the tested range, slightly detrimental effect of HES on brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) is observed. Comparision of NO and NO2 emissions is done to understand the non-thermal influence of H2 on the NOx emissions. Hence, HES is found beneficial in reducing harmful emissions at low and mid loads.
Mechanism of improving oxygen transport resistance of polytetrafluoroethylene in catalyst layer for polymer electrolyte fuel cells Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-20 Zhaohui Wan, Sufen Liu, Qing Zhong, Aiping Jin, Mu Pan
Oxygen transport resistance of catalyst layer (CL) has significant impact on the performance for polymer electrolyte fuel cells (PEFCs). Nano-Polytetrafluoroethylene (PTFE) particles are added into CL to improve the oxygen transport resistance. The CV curves indicate that PTFE do not reduce the utilization of Pt. The I V polarization curves suggest that the performance incorporated PTFE in CL gradually improve at high current densities and the output is 0.57 V at 1.8 A cm−2, 70 mV higher than that without PTFE. The water contact angle for CL with 20 wt% PTFE shows that continuous hydrophobic network may not be formed at 150 °C heat treatment temperature. The total transport resistance of CL with PTFE decreases about 2.5% at 70 °C and 250 kPa, mainly caused by the reduction of pressure-independent resistance (Rother). In the Rother reduction, the Knudsen diffusion resistance reduction in CL account for 74%. The pore size distributions reveal that the porosity increases 29% and the proportion of pores at around 100 nm increases for primary pores in CL with PTFE. This finding indicates that not the hydrophobicity of PTFE but the porous structure conducive to Knudsen diffusion for CL plays the predominant role in improving the performance.
Effects of steam dilution on laminar flame speeds of H2/air/H2O mixtures at atmospheric and elevated pressures Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Yajin Lyu, Penghua Qiu, Li Liu, Chenchen Yang, Shaozeng Sun
The laminar flame speeds of H2/air with steam dilution (up to 33 vol%) were measured over a wide range of equivalence ratio (0.9–3.0) at atmospheric and elevated pressures (up to 5 atm) by an improved Bunsen burner method. Burke, Sun, HP (High Pressure H2/O2 mechanism), and Davis mechanisms were employed to calculate the laminar flame speeds and analyze different effects of steam addition. Four studied mechanisms all underestimated the laminar flame speeds of H2/air/H2O mixtures at medium equivalence ratios while the Burke mechanism provided the best estimates. When the steam concentration was lower than 12%, increasing pressure first increased and then decreased the laminar flame speed, the inflection point appeared at 2.5 atm. When the steam concentration was greater than 12%, increasing the pressure monotonously decrease the laminar flame speed. The chemical effect was amplified by elevated pressure and it played an important role for the inhibiting effect of the pressure on laminar flame speed. The fluctuations of the chemical effect at 1 atm were mainly caused by three-body reactions, while the turn at 5 atm was mainly caused by the direct reaction effect. Elevated pressure and steam addition amplified the influences of uncertainties in the rate constants for elementary reactions, which might leaded to the disagreement between experimental and simulation results.
Preparation of carbon nanotube and graphene doped polyphenylene sulfide flexible film electrodes and the electrodeposition of Cu2O nanocrystals for hydrogen-generation Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Yaxin Zhou, Lingpu Jia, Tingxia Wang, Yongling Du, Chunming Wang
Through annealing and electrochemical reduction methods, we successfully fabricates reduced graphene oxide layer (RGOL) modified carbon nanotube and reduced graphene oxide (CNT + RGO) doped polyphenylene sulfide (PPS) flexible thin film electrodes. These composite structure films can not only overcome the brittle nature of PPS, but also make good use of the thermal stability of PPS. Furthermore, carbon nanotube and reduced graphene oxide enhance the electrical conductivity of the composite films. Truncated octahedral and cuboctahedral Cu2O nanocrystals are synthesized on RGOL modified CNT + RGO doped PPS (RGOL@PPS/CNT + RGO) composite film by a facile electrodeposition method without using any surfactants or external heating. RGOL on the PPS/CNT + RGO substrate facilitates the formation of Cu2O morphology. The obtained Cu2O composite film shows a superior ability for the hydrogen evolution reaction (HER) compared with other Cu2O electrocatalysts. The Cu2O with a smaller loading less than 0.04 mg cm−2 on the composite film exhibits excellent HER activities with a low onset potential of 0.05 V and large current densities. The results of the HER performance indicates that the RGOL@PPS/CNT + RGO composite film has a potential application in flexible hydrogen-producing devices.
Mg-based composites for enhanced hydrogen storage performance Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Mi Tian, Congxiao Shang
Hydrogen storage in solids of hydrides is advantageous in comparison to gaseous or liquid storage. Magnesium based materials are being studies for solid-state hydrogen storage due to their advantages of high volumetric and gravimetric hydrogen storage capacity. However, unfavorable thermodynamic and kinetic barriers hinder its practical application. In this work, we presented that kinetics of Mg-based composites were significantly improved during high energy ball milling in presence of various types of carbon, including plasma carbon produced by plasma-reforming of hydrocarbons, activated carbon, and carbon nanotubes. The improvement of the kinetics and de-/re-hydrogenation performance of MgH2 and TiC-catalysed MgH2 by introduction of carbon are strongly dependent on the milling time, amount of carbon and carbon structure. The lowest dehydrogenation temperature was observed at 180 °C by the plasma carbon–modified MgH2/TiC. We found that nanoconfinement of carbon structures stabilised Mg-based nanocomposites and hinders the nanoparticles growth and agglomeration. Plasma carbon was found to show better effects than the other two carbon structures because the plasma carbon contained both few layer graphene sheets that served as an active dispersion matrix and amorphous activated carbons that promoted the spill-over effect of TiC catalysed MgH2. The strategy in enhancing the kinetics and thermodynamics of Mg-based composites is leading to a better design of metal hydride composites for hydrogen storage.
Sodium borohydride and propylene glycol, an effective combination for the generation of 2.3 wt% of hydrogen Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Hanane Ould-Amara, Damien Alligier, Eddy Petit, Pascal G. Yot, Umit B. Demirci
Sodium borohydride NaBH4 (SB) readily and completely reacts with four equivalents of propylene glycol HOCH2CH(OH)CH3 (PG), resulting in the liberation of four equivalents of H2 at temperatures starting from 25 °C. Alcoholysis (or glycolysis) takes place. The system SB-4PG is then an attractive H2 generator thanks to an effective gravimetric hydrogen storage capacity of 2.3 wt%. It offers several other advantages: there is no need of catalyst; there is no precipitation of by-product; PG is among the safest alcohols (much safer than e.g. methanol). The potential of SB-4PG as H2 generator is thus illustrated and discussed herein.
Mo remarkably enhances catalytic activity of Cu@MoCo core-shell nanoparticles for hydrolytic dehydrogenation of ammonia borane Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Cong Wang, Hongli Wang, Zhili Wang, Xiaoju Li, Yue Chi, Minggang Wang, Dawei Gao, Zhankui Zhao
Ammonia borane (AB) has been identified as one of the most promising candidates for chemical hydrogen storage. However, the practical application of AB for hydrogen production is hindered by the need of efficient and inexpensive catalysts. For the first time, we report that the incorporation of Mo into Cu@Co core-shell structure can significantly improve the catalytic efficiency of hydrogen generation from the hydrolysis of AB. The Cu0.81@Mo0.09Co0.10 core-shell catalyst displays high catalytic activity towards the hydrolysis dehydrogenation of AB with a turnover frequency (TOF) value of 49.6 molH2 molcat−1 min−1, which is higher than most of Cu-based catalysts ever reported, and even comparable to those of noble-metal based catalysts. The excellent catalytic performance is attributed to the multi-elements co-deposition effect and electrons transfer effect of Cu, Mo and Co in the tri-metallic core-shell NPs.
The effect of Nafion membrane fouling on the power generation of a microbial fuel cell Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Sami G.A. Flimban, Sedky H.A. Hassan, Md. Mukhlesur Rahman, Sang-Eun Oh
Microbial fuel cells (MFCs) are the most useful technologies for energy production and wastewater treatment due to their low cost and support of the environment. In this study, the membrane fouling and their effects on power generation were investigated using scanning electron microscope (SEM). Results demonstrate that proton exchange membrane (PEM) was affected by biofouling in a two-chamber H-type MFC, which would significantly affect coulombic efficiencies (CEs), and maximum power densities leading to reduced power generation. The power densities of both rice straw and potato peels were 119.35 mW/m2 and 152.55 mW/m2, respectively. Scanning Electron Microscope (SEM) showed substantial accumulation of bacteria and their end-products forming a thick biofilm on the surface of PEM leading to a decrease, if not, preventing the passage of protons from the anode side toward the cathode side. The decline in power generation may result mainly from the biofouling, not of electrodes but, of PEM membrane from both sides (Anode and Cathode) because of improper regular PEM cleaning.
Fe-Cu coated nickel mesh usage as cathode catalyst for hydrogen evolution reaction Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Esra Telli, Denizhan Özer
Nickel mesh electrodes were used as the working electrode. Iron and copper were electrochemically deposited on the nickel mesh in different amounts. When electrochemical coatings had been carried out, different currents were passed from the circuit at different times and coatings were accumulated at constant load. The prepared electrodes called as FexCux, FexCu3x and FexCu9x and these electrodes have been used for hydrogen evolution reaction (HER). The surface morphologies were investigated by scanning electron microscopy. The HER activity is assessed by recording cathodic current–potential curves, cyclic voltammetry, electrochemical impedance spectroscopy. The results show that FexCu9x catalysts have a compact and porous structure as well as good electrocatalytic activity for the HER in alkaline media.
Effect of addition of Zr, Ni, and Zr-Ni alloy on the hydrogen absorption of Body Centred Cubic 52Ti-12V-36Cr alloy Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Amol Kamble, Pratibha Sharma, Jacques Huot
Novel nanocomposite materials for oxygen and hydrogen separation membranes Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Vladislav A. Sadykov, Alexey V. Krasnov, Yulia E. Fedorova, Anton I. Lukashevich, Yulia N. Bespalko, Nikita F. Eremeev, Pavel I. Skriabin, Konstantin R. Valeev, Oleg L. Smorygo
Design of oxygen and hydrogen separation membranes is the point of current interest in producing syngas from biofuels. Nanocomposites with a high mixed ionic-electronic conductivity are known to be promising materials for these applications. This work aims at studying performance of oxygen and hydrogen separation membranes based on nanocomposites PrNi0.5Co0.5O3-δ + Ce0.9Y0.1O2-δ and Nd5.5WO11.25-δ + NiCu alloy, respectively. A high and stable performance promising for the practical application was demonstrated for these membranes. For oxygen separation membrane CH4 conversion is up to 50% with H2 content in the outlet feed being up to 25% at 900 °C. For reactor with hydrogen separation membrane complete EtOH conversion was achieved at T ∼ 700 °C even at the highest flow rate, and a high hydrogen permeation (≥1 ml H2 cm−2 min−1) was revealed.
Effect of CeO2 on oxidation and electrical behaviors of ferritic stainless steel interconnects with Ni Fe coatings Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Peng Fei You, Xue Zhang, Hai Liang Zhang, Hui Jun Liu, Chao Liu Zeng
Ferritic stainless steels are promising materials for application in interconnects of solid oxide fuel cells (SOFC). The present problems to be solved urgently for using ferritic stainless steels as interconnects are their rapid increase in electrical resistance and the cathode poisoning caused by evaporation of chromia. In the present study, the Ni Fe and NiFe CeO2 alloy coatings have been electro-deposited onto 430 stainless steels (430SS). During oxidation at 800 °C in air, an outer dense NiFe2O4 layer and an inner protective Cr2O3 layer have thermally grown on the coated samples. The NiFe2O4 layer retards the outward migration of chromium effectively. The addition of CeO2 reduces the growth rate of Cr2O3 and decreases the number of pores near the oxide scale/alloy interface. Moreover, a higher electrical conductivity has been achieved by the addition of CeO2.
Techno-economic feasibility of fleets of far offshore hydrogen-producing wind energy converters Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Aurélien Babarit, Jean-Christophe Gilloteaux, Gaël Clodic, Maxime Duchet, Alexandre Simoneau, Max F. Platzer
Innovative solutions need to be developed for harvesting wind energy far offshore. They necessarily involve on-board energy storage because grid-connection would be prohibitively expensive. Hydrogen is one of the most promising solutions. However, it is well-known that it is challenging to store and transport hydrogen which may have a critical impact on the delivered hydrogen cost. In this paper, it is shown that there are vast areas far offshore where wind power is both characterized by high winds and limited seasonal variations. Capturing a fraction of this energy could provide enough energy to cover the forecast global energy demand for 2050. Thus, scenarios are proposed for the exploitation of this resource by fleets of hydrogen-producing wind energy converters sailing autonomously. The scenarios include transportation and distribution of the produced hydrogen. The delivered hydrogen cost is estimated for the various scenarios in the short term and in the longer term. Cost estimates are derived using technical and economic data available in the literature and assumptions for the cost of electricity available on-board the wind energy converters. In the shorter term, delivered cost estimates are in the range 7.1–9.4 €/kg depending on the scenario and the delivery distance. They are based on the assumption of on-board electricity cost at 0.08€/kWh. In the longer term, assuming an on-board electricity cost at 0.04€.kWh, the cost estimates could reduce to 3.5 to 5.7 €/kg which would make the hydrogen competitive on several hydrogen markets without any support mechanism. For the hydrogen to be competitive on all hydrogen markets including the ones with the highest GHG emissions, a carbon tax of approximately 200 €/kg would be required.
A strategy for regulating the performance of DCFC with semi-coke fuel Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Guoyang Liu, Yating Zhang, Jiangtao Cai, Anning Zhou, Yongqiang Dang, Jieshan Qiu
Facile synthesis of MoS2/N-doped macro-mesoporous carbon hybrid as efficient electrocatalyst for hydrogen evolution reaction Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-19 Xiaoling Chen, Kangning Zhang, Zhenzhen An, Lina Wang, Yan Wang, Sen Sun, Tong Guo, Dongxia Zhang, Zhonghua Xue, Xibin Zhou, Xiaoquan Lu
(In, Cu) Co-doped ZnS nanoparticles for photoelectrochemical hydrogen production Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Gang-Juan Lee, Hui-Chuan Chen, Jerry J. Wu
Crosswise stream of hydrogen-oxide (H2O) through a porous media containing copper nanoparticles Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Rashid Mehmood, R. Tabassum, O. Pourmehran, D.D. Ganji
Transport theories in porous media are quite operative to analyse heat transferral phenomenon in biological tissues, reducing bio convective flow instabilities by means of porous media and many more. Inspired by these remarkable features, the present study is conducted to analyse heat transfer phenomenon for obliquely striking nanofluid through a porous media. Copper (Cu) nanoparticles are suspended in traditional Hydrogen Oxide based fluid. Scaling group of transformations is conveniently employed to reduce governing transport equations and is tackled numerically afterwards. Influence of nanoparticles volume fraction, stretching ratio and porosity parameter on physical measures of concern such as normal and tangential skin friction and corresponding heat flux at wall is portrayed. Streamline patterns are traced out to discover the influence of porosity factor on actual flow behavior. It was observed that solid volume fraction of copper nanoparticles enhanced the skin friction coefficients and heat flux. Increasing the porosity parameter leads to greater heat flux and tangential skin friction co-efficient.
Ni supported on CaO-MgO-Al2O3 as a highly selective and stable catalyst for H2 production via the glycerol steam reforming reaction Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 N.D. Charisiou, K.N. Papageridis, L. Tzounis, V. Sebastian, S.J. Hinder, M.A. Baker, M. AlKetbi, K. Polychronopoulou, M.A. Goula
A comparative study of the GSR performance for Ni/CaO-MgO-Al2O3 and Ni/Al2O3 catalysts is reported. Catalysts were synthesized applying the wet impregnation method at a constant metal loading (8 wt %). Synthesized samples were characterized by N2 adsorption/desorption, ICP, BET, XRD, NH3-TPD, CO2-TPD, H2-TPR, XPS, TEM, STEM-HAADF and EDS. The carbon deposited on their surface under reaction conditions was characterized by TPO, Raman and TEM. It was proven that the use of CaO-MgO as alumina modifiers leads to smaller nickel species crystallite size, increased basicity and surface amount of Ni0 phase. Thus, it increases the conversion to gaseous products favoring H2 and CO2 production to the detriment of CO formation, by enhancing the water gas-shift (WGS) reaction. No liquid products were produced by the Ni/modAl catalyst over 550 °C, whereas time on stream results confirmed that deactivation can be prevented, as apart from decreasing the amount of coke deposition the nature of carbon was altered towards less graphitic and more defective structures.
PtRu nanoalloys loaded on graphene and TiO2 nanotubes co-modified Ti wire as an active and stable methanol oxidation electrocatalyst Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Jingsong Han, Liming Yang, Lixia Yang, Wenjing Jiang, Xubiao Luo, Shenglian Luo
Exploring a novel ceramic (Ti,W)3SiC2 for interconnect of intermediate temperature solid oxide fuel cell Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Lili Zheng, Qingsong Hua, Xichao Li, Meishuan Li, Yuhai Qian, Jingjun Xu, Zuoqiang Dai, Hongxin Zhang, Tiezhu Zhang, Junwei Wu
A solid solution (Ti,W)3SiC2 possessing good oxidation resistance and low area-specific resistance (ASR) after oxidation has been synthesized by an in-situ hot pressing process. The oxidation rate constant at 800 °C in air is 6.29 × 10−14 g2 cm−4 s−1 for (Ti,W)3SiC2. The formed single-layer oxide is composed of W doped rutile TiO2 and amorphous SiO2. SiO2 is evenly inlaid in the communicative body frame of TiO2. W doped in TiO2 mainly exists as W6+. W doping not only hinders the outward diffusion of Ti by decreasing the concentration of native Ti interstitials in TiO2, but also restrains the inward diffusion of oxygen by decreasing the concentration of O vacancies. Furthermore, W dopant in TiO2 enhances the electrical conductivity of TiO2 by increasing the concentration of semi-free electron. Therefore, the low ASR of (Ti,W)3SiC2 after oxidation owes to high electrical conductivity of TiO2 as well as the reduced thickness of oxide scale. All the results render (Ti1-xWx)3SiC2 promising as interconnects for the intermediate temperature solid oxide fuel cell.
Effect of additive distribution in H2 absorption and desorption kinetics in MgH2 milled with NbH0.9 or NbF5 Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Santiago A. Pighin, Bruno Coco, Horacio Troiani, Facundo J. Castro, Guillermina Urretavizcaya
This paper presents a comparative study of H2 absorption and desorption in MgH2 milled with NbF5 or NbH0.9. The addition of NbF5 or NbH0.9 greatly improves hydriding and dehydriding kinetics. After 80 h of milling the mixture of MgH2 with 7 mol.% of NbF5 absorbs 60% of its hydrogen capacity at 250 °C in 30 s, whereas the mixture with 7 mol.% of NbH0.9 takes up 48%, and MgH2 milled without additive only absorbs 2%. At the same temperature, hydrogen desorption in the mixture with NbF5 finishes in 10 min, whereas the mixture with NbH0.9 only desorbs 50% of its hydrogen content, and MgH2 without additive practically does not releases hydrogen. The kinetic improvement is attributed to NbH0.9, a phase observed in the hydrogen cycled MgH2 + NbF5 and MgH2 + NbH0.9 materials, either hydrided or dehydrided. The better kinetic performance of the NbF5-added material is attributed to the combination of smaller size and enhanced distribution of NbH0.9 with more favorable microstructural characteristics. The addition of NbF5 also produces the formation of Mg(HxF1-x)2 solid solutions that limit the practically achievable hydrogen storage capacity of the material. These undesired effects are discussed.
Application of microwave synthesized Ag-Rh nanoparticles in cyclohexane dehydrogenation for enhanced H2 delivery Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Jayshri V. Pande, Ankush B. Bindwal, Yogesh B. Pakade, Rajesh B. Biniwale
The catalytic dehydrogenation of liquid organic hydrides (LOH) is a promising route to deliver H2 for various mobile and stationary applications. However, an efficient and low-cost dehydrogenation catalyst, as an alternative to Pt, is a key for the success of LOH-based H2 supply. In a quest for such catalysts, we synthesized stable Ag-Rh bimetallic nanoparticles (BNP) supported on activated carbon cloth (ACC) and Y2O3 using the microwave-assisted polyol technique. The performance of these catalysts during dehydrogenation of LOH viz., cyclohexane, was evaluated at 300 °C using an advanced spray-pulse reactor system. The Ag:Rh ratio was optimized to maximize the cyclohexane conversion and H2 evolution. The effect of Ag:Rh ratio, catalyst support, and synthesis method was investigated, too. The most stable H2 evolution performance was exhibited by microwave-synthesized 1:4 Ag-Rh/Y2O3 catalyst with the cyclohexane conversion, dehydrogenation rate and H2 evolution rate of 35.8%, 17.2 mmol/gMet/min and 400 mmol/gMet/min, respectively. Finally, the performance of catalysts used in this study was compared with the Pt-based catalysts.
Ternary nickel iron phosphide supported on nickel foam as a high-efficiency electrocatalyst for overall water splitting Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Chi Zhang, Yunchao Xie, Heng Deng, Cheng Zhang, Jheng-Wun Su, Yuan Dong, Jian Lin
Electrochemical water splitting is a promising technology for mass hydrogen production. Efficient, stable, and cheap electrocatalysts are keys to realizing this strategy. However, high price and preciousness of commonly used noble metal based catalysts severely hinder this realization. Herein, we report nickel iron phosphide (Ni-FexP) bifunctional electrocatalyst via the in-situ growth of Ni Fe(OH)x on nickel foam (Ni Fe(OH)x/NF) followed by low-temperature phosphidation. As a hydrogen evolution reaction (HER) catalyst, the Ni-FexP/NF only needs an overpotential of 119 mV to drive a current density of −10 mA/cm2 in a base media. It also shows excellent activity toward oxygen evolution reaction (OER) with low overpotentials of 254 mV, 267 mV, and 282 mV at 50, 100 and 200 mA/cm2, respectively. Moreover, when this bifunctional catalyst is used for overall water splitting, a low cell voltage of 1.62 V is needed to deliver a current density of 10 mA/cm2, which is superior to commercial electrolyzer and it also shows remarkable stability.
Improved electrochemical hydrogen storage performance of Ti49Zr26Ni25 quasicrystal alloy by doping with mesoporous α-Fe2O3 particles Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Heng Liu, Xiaojie Zhai, Zhe Li, Xing Tao, Wanqiang Liu, Jianxun Zhao
A Ti49Zr26Ni25 quasicrystal alloy was prepared by mechanical alloying and subsequent annealing. Mesoporous α-Fe2O3 particles were obtained via a hydro-thermal procedure using chitosan as the template. Composites of Ti49Zr26Ni25 mixed with different amounts of mesoporous α-Fe2O3 were synthesized to enhance the electrochemical properties of Ti49Zr26Ni25. The structural characteristics of the alloy and composites were investigated using XRD, SEM, TEM and BET analysis. The electrochemical properties of the composite electrodes were tested using a three-electrode battery system at room temperature. The discharge capacities for the composites were higher than those for the Ti49Zr26Ni25 alloy and reached a maximum (259.6 mAh/g) for 5% additive content of α-Fe2O3. Moreover, the composites showed enhanced high-rate dischargeability. The capacity decay rate and charge-transfer resistance decreased after α-Fe2O3 loading. The preferable performance of the composite alloys may be attributed to the doping of mesoporous α-Fe2O3, which may play a catalytic effect in the kinetics of the electrochemical reactions. The large surface area and mesoporous structure of α-Fe2O3 may also be advantageous for rapid transmission of hydrogen in the interior of the alloy, thus improving the discharge capacity of the alloy electrode.
Surface modification of aligned TiO2 nanotubes by Cu2O nanoparticles and their enhanced photo electrochemical properties and hydrogen generation application Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Pawan Kumar Dubey, Rajesh Kumar, Radhey Shyam Tiwari, Onkar Nath Srivastava, Avinash Chandra Pandey, Prabhakar Singh
On the effect of gas channels-electrode interface area on SOFCs performance Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Julio Moreno-Blanco, Francisco Elizalde-Blancas, Jose M. Riesco-Avila, Juan M. Belman-Flores, Armando Gallegos-Muñoz
In this work a detailed analysis of the overpotentials inherent during the operation of a solid oxide fuel cell (SOFC) is presented. The study is performed in order to evaluate the effect of the design of the current collectors on SOFCs performance. The analysis is carried out by means of numerical simulations in different current collector configurations consisting of straight channels in which their width is varied. Special attention is paid in the ohmic and concentration losses which are directly related with the design of the current collectors. Polarization and power density curves are obtained for different current collector designs operating at the same conditions. The ohmic losses were directly affected by the ratio between the gas channels-electrode interface area and the active area. Increasing or decreasing the area ratio around a certain value causes the ohmic losses to increase exponentially. Moreover, the concentration losses showed an opposite behavior when compared with the ohmic losses. The best performance was obtained when the ratio between the gas channels-electrode interface area and the active area is about 0.36.
Effects of congestion and confining walls on turbulent deflagrations in a hydrogen storage facility-part 1: Experimental study Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 L.C. Shirvill, T.A. Roberts, M. Royle, D.B. Willoughby, P. Sathiah
If the general public is to use hydrogen as a vehicle fuel, customers must be able to handle hydrogen with the same degree of confidence, and with comparable risk, as conventional liquid and gaseous fuels. Since hydrogen is stored and used as a high-pressure gas, a jet release in a confined or congested area can create an explosion hazard. Therefore, hazards associated with jet releases from leaks in a vehicle-refuelling environment must be considered. As there was insufficient knowledge of the explosion hazards, a study was initiated to gain a better understanding of the potential explosion hazard consequences associated with high-pressure leaks from hydrogen vehicle refuelling systems. Our first paper  describes the release and subsequent ignition of a high-pressure hydrogen jet in a simulated dispensing area of a hydrogen vehicle refuelling station. In the present paper, an array of dummy storage cylinders with confining walls (to represent isolation from the forecourt area) was used to represent high-pressure hydrogen cylinder storage congestion. Experiments with ignition of premixed 5.4 m × 6.0 m × 2.5 m hydrogen-air clouds and hydrogen jet releases up to 40 MPa pressures were performed. The results are presented and discussed in relation to the conditions giving the highest overpressures. We concluded from the study that the ignition of a jet release gives much higher local overpressure than in the case of ignition of a homogeneous mixture inside the cylinder storage congestion area. The modelling of these results will be presented in Part 2 of this paper.
Technical evaluation of post-combustion CO2 capture and hydrogen production industrial symbiosis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-17 Adeel Ghayur, T. Vincent Verheyen
The aim of this study is to develop an industrial ecosystem whereby wastes/products from a Post-combustion CO2 Capture (PCC) plant are utilised in a hydrogen biorefinery. Subsequently, five hydrogen biorefinery models are developed that use PCC's model amine i.e. monoethanolamine (MEA) as a nitrogen source during microbial hydrogen production and CO2 as a process chemical. Technical evaluations of the five case models are carried out to identify the ones that maximise value by multiproduct generation from biomass and fulfil total/partial parasitic energy demand. The case meeting these criteria, produces 3.1t of succinylated lignin adhesive, 4.9t of dry compost and 2744 kWh of electricity from 10t (dry) of sawdust feedstock, daily. Its daily power and heat duties stand at 3906 kWh and 52.1 GJ respectively. Simulations also demonstrate biohydrogen's potential as an energy storage vector for peak/backup power with an annual 1001.4 MWh of power storage capacity from 10t/d feedstock.
Investigation on energy storage and conversion properties of multifunctional PANI-MWCNT composite Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Atanu Roy, Apurba Ray, Samik Saha, Sachindranath Das
Polyaniline-multiwalled carbon nanotube (PANI-MWCNT) composite synthesized through chemical polymerization is investigated as a possible electrode material for supercapacitor as well as an electro-catalyst for hydrogen evolution reaction (HER) in acidic medium. UV–Vis spectroscopy, FTIR spectroscopy and field emission scanning electron microscopy (FESEM) have been used to characterize the electrode material. The binder-free electrodes were prepared and they exhibit a specific capacitance of 540.29 F g−1 at a scan rate of 2 mV s−1 in 1 M H2SO4 electrolyte. The material exhibits excellent pseudocapacitive behaviour due to the presence of PANI with long-term cyclic stability of 87.4% retention after 5000 cycles. PANI-MWCNT composite also shows good HER activity, with overpotential of −395 mV.
Hydrogen bioproduction with anaerobic bacteria consortium from brewery wastewater Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Renan Pachiega, Mayara Franco Rodrigues, Caroline Varella Rodrigues, Isabel Kimiko Sakamoto, Maria Bernadete A. Varesche, José Eduardo De Oliveira, Sandra Imaculada Maintinguer
Biohydrogen production is a cheap and clean way to obtain hydrogen gas. In subtropical countries such as Brazil the average temperatures of 27 °C can favor the hydrogen producing bacteria growth. A mixed culture was obtained from a subtropical sludge treating brewery wastewater and anaerobic batch reactors were fed with glucose, sucrose, fructose and xylose in low concentrations (2.0, 5.0 and 10.0 g L−1) at 37 °C, initial pH 5.5 and headspace with N2 (99%) to maintain the anaerobic conditions. The inoculum was a subtropical granulated sludge from UASB (Upflow Anaerobic Sludge Blanket) reactor treating brewery wastewater. The higher H2 yields were obtained in reactors operated with 2 and 5 g L−1 of fructose and they were 1.5 mol H2 mol−1 of fructose and 1.3 mol H2 mol−1 of sucrose, respectively. The volatile fatty acids (VFA) generated at the end of operation were, predominantly, butyric and acetic acid, indicating the favoring of the metabolic route of hydrogen generation by the consortium of anaerobic bacteria from the brewery wastewater. Biomolecular analyses revealed the predominance of hydrogen producing bacteria from Firmicutes phylum distributed in the families Streptococcaceae, Veillonellaceae and uncultured bacteria. These results confirm future applications of subtropical sludges with agroindustrial wastewaters containing low concentrations of sugars on hydrogen generation.
Texture dependence of hydrogen diffusion in nanocrystalline nickel by atomistic simulations Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Roghayeh Mohammadzadeh, Mina Mohammadzadeh
Atomistic simulations were performed to highlight the importance of the texture on the diffusion of hydrogen atoms in nanocrystalline nickel. Significant anisotropic diffusion is observed in longitudinal and through thickness directions. Our results show that the diffusion coefficient of hydrogen atoms through thickness in  textured nickel is larger than those values obtained for  and . The diffusivity along longitudinal and transverse directions in  textured samples is found to be higher than that along thickness direction. Additionally, it is determined that the presence of hydrogen atoms changes the vacancy formation of the substrate and the vacancy defects are responsible for the anisotropy of hydrogen diffusion. These findings improve our understanding of hydrogen diffusivity at the atomistic level for hydrogen storage in the materials.
Photoactive TiO2/MoS2 electrode with prolonged stability Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 A. Trenczek-Zajac, J. Banas, M. Radecka
Recent progress in hydrogen production from formic acid decomposition Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Xian Wang, Qinglei Meng, Liqin Gao, Zhao Jin, Junjie Ge, Changpeng Liu, Wei Xing
Formic acid, as the simplest carboxylic acid which can be obtained as an industrial by-product, is colorless, low toxicity, and easy to transport and storage at room temperature. Recently, Formic acid has aroused wide-spread interest as a promising material for hydrogen storage. Compared to other organic small molecules, the temperature for formic acid decomposition to produce hydrogen is lower, resulting in less CO toxicant species. Lots of catalysts on both homogeneous catalysts and heterogeneous were reported for the decomposition of formic acid to yield hydrogen and carbon dioxide at mild condition. In this paper, the recent development of mechanism and the material study for both homogeneous catalysts and heterogeneous catalysts are reviewed in detail.
Synthesis and characterization of Zr-promoted Ni-Co bimetallic catalyst supported OMC and investigation of its catalytic performance in steam reforming of ethanol Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Vahid Shahed gharahshiran, Mardali Yousefpour
Hydrogen evolution from hydrolysis of ammonia borane catalyzed by Rh/g-C3N4 under mild conditions Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Rui Lu, Min Hu, Caili Xu, Yi Wang, Yun Zhang, Bin Xu, Daojiang Gao, Jian Bi, Guangyin Fan
Developing effective catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) is of great significance considering the useful applications of hydrogen. Herein, graphitic carbon nitride (g-C3N4) prepared through the simply pyrolysis of urea was employed as a support for Rh nanoparticles (NPs) stabilization. The in-situ generated Rh NPs supported on g-C3N4 with an average size of 3.1 nm were investigated as catalysts for hydrogen generation from the hydrolysis of AB under mild conditions. The Rh/g-C3N4 catalyst exhibits a high turnover frequency of 969 mol H2· (min·molRh)−1 and a low activation energy of 24.2 kJ/mol. The results of the kinetic studies show that the catalytic hydrolysis of AB over the Rh/g-C3N4 catalyst is a zero-order reaction with the AB concentration and a first-order reaction with the Rh concentration. This work demonstrates that g-C3N4 is a useful support to design and synthesis of effective Rh-based catalyst for hydrogen-based applications.
Hydrogen adsorption in metal- organic frameworks (MOFs): Effects of adsorbent architecture Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Siroos Rostami, Ali Nakhaei Pour, Alireza Salimi, Arghavan Abolghasempour
Production and use of HHO gas in IC engines Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-16 Balaji Subramanian, Saleel Ismail
HHO gas, which is obtained by the electrolysis of water, is a promising alternative fuel. This paper presents a review of important features and techniques used for producing HHO gas. Various aspects of the thermodynamics and chemical kinetics of electrolysis reactions are discussed. Design and operating parameters for improving the gas production rate are identified. Widely different hypotheses regarding the structure and composition of HHO gas are compared in depth. The state of the art on the use of HHO gas in Internal Combustion (IC) engines is presented in the latter part of the paper. It is seen that the introduction of HHO gas increases engine torque, power and thermal efficiency, while simultaneously reducing the formation of NOx, CO, HC and CO2. The major challenges in using HHO gas in engines are identified as system complexity, safety, cost and efficiency of electrolysis.
Characterization of a circular 80 mm anode supported solid oxide fuel cell (AS-SOFC) with anode support produced using high-pressure injection molding (HPIM) Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-15 Jakub Kupecki, Ryszard Kluczowski, Davide Papurello, Andrea Lanzini, Michał Kawalec, Mariusz Krauz, Massimo Santarelli
The current study was oriented at analyzing the performance of an anode-supported solid oxide fuel cell produced using high-pressure injection molding. The cell with a total thickness of 550 μm was produced in the Ceramic Department (CEREL) of the Institute of Power Engineering in Poland and experimentally analyzed in the Energy Department (DENERG) of Politecnico di Torino in Italy. The high-pressure injection molding technique was applied to produce a 500 μm thick anode support NiO/8YSZ 66/34 wt% with porosity of 25 vol%. The screen printing method was used to print a 3 μm thick NiO anode contact layer, 7 μm thick NiO/8YSZ 50/50 wt% anode functional layer, 4 μm thick 8YSZ dense electrolyte, 1.5 μm thick Gd0,1Ce0,9O2 barrier layer and a 30 μm thick La0,6Sr0,4Fe0,8Co0,2O3–δ cathode with porosity 25 vol%. The experimental characterization was done at two temperature levels: 750 and 800 °C under fixed anodic and cathodic flow and compositions. The preliminary studies on the application of high-pressure injection molding are discussed together with the advantages of the technology. The performance of two generations of anode-supported cells is compared with data of reference cells with supports obtained using tape casting.
Engine speed and air-fuel ratio effect on the combustion of methane augmented hydrogen rich syngas in DI SI engine Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-15 Ftwi Yohaness Hagos, A. Rashid A. Aziz, Shaharin A. Sulaiman, Rizalman Mamat
The main challenge on the fueling of pure hydrogen in the automotive vehicles is the limitation in the hydrogen separation from the product of steam reforming and gasification plants and the storage issues. On the other hand, hydrogen fueling in automotive engines has resulted in uncontrolled combustion. These are some of the factors which motivated for the fueling of raw syngas instead of further chemical or physical processes. However, fueling of syngas alone in the combustion chamber has resulted in decreased power output and increased in brake specific fuel consumption. Methane augmented hydrogen rich syngas was investigated experimentally to observe the behavior of the combustion with the variation of the fuel-air mixture and engine speed of a direct-injection spark-ignition (DI SI) engine. The molar ratio of the high hydrogen syngas is 50% H2 and 50% CO composition. The amount of methane used for augmentation was 20% (V/V). The compression ratio of 14:1 gas engine operating at full throttle position (the throttle is fully opened) with the start of the injection selected to simulate the partial DI (180° before top dead center (BTDC)). The relative air-fuel ratio (λ) was set at lean mixture condition and the engine speed ranging from 1500 to 2400 revolutions per minute (rpm) with an interval of 300 rpm. The result indicated that coefficient of variation of the indicate mean effective pressure (COV of IMEP) was observed to increase with an increase with λ in all speeds. The durations of the flame development and rapid burning stages of the combustion has increased with an increase in λ. Besides, all the combustion durations are shown to be more sensitive to λ at the lowest speed as compared to the two engine speeds.
ZnO/Polytyramine nanocomposite film: Facile electrosynthesis and high performance electrocatalytic activity toward methanol oxidation Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-03-15 Lida Fotouhi, Nasrin Fathali, Ali Ehsani
In the present study, the methanol oxidation reaction was investigated on a nickel ion incorporated to the zinc oxide-sodium dodecyl sulfate-polytyramine (ZnO-SDS-Pty) nanocomposite film by cyclic voltammetry and chronoamperometry. ZnO-SDS-Pty nanocomposite was prepared by using the repeated potential cyclic voltammetry in a solution containing ZnO nanoparticles and tyramine in an acidic solution of SDS by cycling the potential. The electrochemical oxidation of methanol was investigated by a stable redox behavior of the Ni(III)/Ni(II) couple at the potential of 0.4 V, after the immersion of the modified electrode (ZnO-SDS-Pty/G) in an alkaline media (i.e. NaOH 0.1 molL−1) of nickel chloride solution. The electrochemical characterization of the modified electrode exhibited that the ZnO-SDS-Pty nanocomposite, electrodeposited on the electrode surface, improved the catalytic efficiency of the dispersed nickel ions toward methanol oxidation. The catalytic rate constant and diffusion coefficient of the methanol oxidation reaction were calculated by chronoamperometry. The Ni-ZnO-SDS-Pty nanocomposite displayed a highly stable response during the oxidation of methanol, proving to be a suitable electrode material in methanol fuel cells.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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