Hydraulic ex situ through-plane characterization of porous transport layers in PEM water electrolysis cells Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Kolja Bromberger, Jagdishkumar Ghinaiya, Thomas Lickert, Arne Fallisch, Tom Smolinka
This paper describes new methods to characterize the hydraulic behavior of porous transport layers (PTL) by using capillary flow porometry (CFP). We present the standard procedure of CFP to gain access to the biggest pore, the mean flow pore and the smallest pore size as well as the absolute through-plane gas permeability of PTLs. An extended method is introduced to measure the relation of capillary pressure versus liquid saturation. It is shown that capillary pressure has a significant influence on mass transport limitation (MTL) in PEM electrolysis cells using a flow field. Furthermore, a new method is proposed to measure the intrinsic contact angle of PTLs by using water and a reference liquid with a contact angle of zero. It is shown that knowing the pore size distribution and the contact angle is essential for studying the influence on capillary pressure. In the course of this study results of CFP are compared to results from mercury porosimetry. We prove that the contact angle is strongly influenced by the titanium oxide layer which forms during electrolysis operation due to electrochemical oxidation of titanium. In summary, we propose a simple key parameter that describes the ability of partially saturated PTLs to transport gas in through-plane direction, termed gas transportability. The latter is introduced and employed to analyze polarization curves of different PTLs.
Automation and analysis of the operation of (La0.85Ce0.15)Ni5 in energy storage plants Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 F. Gonzatti, M. Miotto, F.A. Farret
The hydrogen storage phase of an energy storage plant based on metallic hydrides has a strong influence on the total efficiency of storage power plants as well as on their response time. The technique presented in this paper uses a hydrogen-metal chemical bond during its storage. This paper describes a metal hydride cylinder modeled and simulated by using the main quantities involved in the adsorption and desorption processes as well as in an analysis of the influence of thermal quantities involved in these processes. As a result, a proposal for automation of the thermal exchange of the modeled cylinder is presented and the possibilities of evaluation of this technique.
Transition metal decorated covalent triazine-based frameworks as a capacity hydrogen storage medium Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Hongsheng He, Xiaowei Chen, Weidong Zou, Renquan Li
From ab initio density functional theory (DFT) calculations, the structural stability and hydrogen adsorption capacity of transition metal (TM, TM = Sc, Ti, V, Cr, Mn) decorated covalent triazine-based framework (CTF) are discussed. It is found that by calculation, these TM atoms can adsorb on the CTF sheet without clusters. The Sc, Ti, V, Cr and Mn decorated CTF are predicated to bind five, four, three, three and two of hydrogen molecules. We found that Sc and Ti decorated CTF are suitable candidates for effective reversible hydrogen storage at near ambient condition, whereas V, Cr and Mn decorated CTF are not promising materials due to too large average bind energies per hydrogen molecule.
Efficient electrocatalytic and photocatalytic hydrogen evolution using a linear trimeric thiolato complex of nickel Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 An Xie, Jie Zhu, Geng-Geng Luo
Chemical kinetic modeling of ammonia oxidation with improved reaction mechanism for ammonia/air and ammonia/hydrogen/air combustion Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Junichiro Otomo, Mitsuo Koshi, Teruo Mitsumori, Hiroshi Iwasaki, Koichi Yamada
Study of cyclic performance of V-Ti-Cr alloys employed for hydrogen compressor Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Suganthamalar Selvaraj, Ankur Jain, Sanjay Kumar, Tengfei Zhang, Shigehito Isobe, Hiroki Miyaoka, Yoshitsugu Kojima, Takayuki Ichikawa
Fabrication of 3D Ni nanosheet array on Crofer22APU interconnect and NiO-YSZ anode support to sinter with small-size Ag nanoparticles for low-temperature sealing SOFCs Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Xiaoqing Si, Jian Cao, Sheng Liu, Xiaoguo Song, Junlei Qi, Yongxian Huang, Jicai Feng
WSe2/rGO hybrid structure: A stable and efficient catalyst for hydrogen evolution reaction Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Jing Li, Ping Liu, Yan Qu, Tingdi Liao, Bin Xiang
Exergy analysis on non-catalyzed partial oxidation reforming using homogeneous charge compression ignition engine in a solid oxide fuel cell system Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Sechul Oh, Han Ho Song
Based on the recent improvements in high-temperature fuel cells, distributed power generation fuel cell system of small scale (∼hundreds kilowatts) has been widely investigated. To improve the system efficiency, most developments focused on the fuel cell stack, but little was paid attention to the intrinsic exergy destructions at the other parts of a typical configuration. The main objective of this study is to investigate a feasibility of reducing the exergy destruction in the reforming process of fuel cell system, by using a homogeneous charge compression ignition (HCCI) engine as a replacement of existing reforming subsystems, i.e. steam methane reforming (SMR), partial oxidation (POX), or autothermal reforming (ATR), in a solid oxide fuel cell (SOFC) system. To do this, parametric studies with exergy analysis were conducted by using in-house 1-D SOFC and 0-D HCCI simulation models. In results, due to the work production from HCCI reforming engine in addition to the work of the fuel stack, it is demonstrated that HCCI-SOFC system has higher system efficiency than partial oxidation (POX) and autothermal reforming (ATR) systems, which use similar partial oxidation reaction for reformer operation. Furthermore, because of no requirement for catalyst, the HCCI system demonstrates wider operating range than that of POX and ATR systems. When compared to the steam methane reforming (SMR)-SOFC system, the HCCI-SOFC system has the lower total work but slightly higher exergetic system efficiency, mainly caused by large amount of heat exergy needed to operate endothermic reforming process in the SMR process. Based on our simulation data, the exergetic efficiency of the HCCI-SOFC system shows 6.0%, 2.1% and 0.4% higher than POX, ATR and SMR systems at the highest efficiency points of each strategy, while 5.5%, 5.8% and 3.8% higher than POX, ATR and SMR systems at 99% methane conversion points in each reformer, respectively.
Hydrogenation of carbon dioxide under atmospheric pressure and low temperature Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Yi Zhao, Xinfeng Qian, Xiaochu Zhao, Zili Zhang
In order to realize the effective reduction and utilization of carbon dioxide (CO2) in coal-fired flue gas, a process was developed under atmospheric pressure that uses KBH4 as an efficient hydrogen donor. By investigating the influencing factors of CO2 conversion, the optimal experimental conditions were determined and the average CO2 conversion efficiency of 50.36% was obtained when the KBH4 concentration was 0.2 mol/L, reaction temperature was 50 °C, solution pH was 8, and flow rate was 300 mL/min. The experimental results also verified that the coexisting gases such as sulfur dioxide (SO2), nitric oxide (NO) and oxygen (O2) in flue gas had no significant competition or inhibition effect on CO2 conversion. Meanwhile, the conversion products were analyzed by an Ion Chromatography (IC) and Fourier Transform Infrared Spectroscopy (FT-IR), and the results proved that the main reaction product was formate. Combined with the relevant literatures, the mechanism of CO2 reaction with KBH4 was proposed.
Influences of different diluents on NO emission characteristics of syngas opposed-flow flame Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Dong He, Weiping Yan
This paper used the opposed-flow flame model and GRI 3.0 mechanism to investigate NO emission characteristics of H2-rich and H2-lean syngas under diffusion and premixed conditions, respectively, and analyzed influences of adding H2O, CO2 and N2 on NO formation from the standpoint of thermodynamics and reaction kinetics. For diffusion flames, thermal route is the dominant pathway to produce NO, and adding N2, H2O and CO2 shows a decreasing manner in lowering NO emission. The phenomenon above is more obvious for H2-rich syngas because it has higher flame temperature. For premixed flames, adding CO2 causes higher NO concentration than adding H2O, because adding CO2 produces more O radical, which promotes formation of NO through NNH + O = NH + NO, NH + O = NO + H and reversed N + NO = N2 + O. And in burnout gas, thermal route is the dominant way for NO formation. Under this paper's conditions, adding N2 increases the formation source of NO as well as decreases the flame temperature, and it reduces the NO formation as a whole. In addition, for H2-lean syngas and H2-rich syngas with CO2 as the diluent, N + CO2 = NO + CO plays as an important role in thermal route of NO formation.
Synthesis and characterization of polymer electrolyte membrane containing methylisatin moiety by polyhydroalkylation for fuel cell Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 Taewook Ryu, Hohyoun Jang, Faiz Ahmed, Nasrin Siraj Lopa, Hanmo Yang, Sujin Yoon, Inhwan Choi, Whangi Kim
Temperature rise of hydrogen storage cylinders by thermal radiation from fire at hydrogen-gasoline hybrid refueling stations Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-12 T. Kuroki, N. Sakoda, K. Shinzato, M. Monde, Y. Takata
This study focuses on two types of hydrogen-gasoline hybrid refueling stations, and a risk assessment study on thermal radiation is carried out with a fire at each hybrid station. One of the hybrid stations has bare hydrogen storage cylinders, and the other has container walls around the cylinders. We calculate radiative flux to the cylinders from the fire occurring at the gasoline refueling machines in each hybrid station. Additionally, we calculate the temperature rise of the cylinders based on the obtained radiative flux. To evaluate a dangerous case for hybrid stations, we calculate the radiative flux and temperature rise using a large scale and high temperature fire. Based on our analysis, we find that the container walls can greatly insulate the radiative flux. Therefore, we show that we are able to keep the temperature of the cylinders below the hazardous temperature of 358 K by installing container walls around them.
Possible causes for the instability in the H2 production from cheese whey in a CSTR Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Elena Castelló, Lucía Braga, Laura Fuentes, Claudia Etchebehere
A CSTR reactor was operated for 30 days. It was fed with raw cheese whey with an organic loading rate of 30 gCOD/Ld. Hydrogen production varied significantly with a maximum of 0.9 LH2/Ld and decreased after 17 days of operation. The causes of production instability were analysed using different microbiological tools. It was concluded that this decrease was not due to the incapacity to select hydrogen-producing organisms, as shown by the persistence of the Fe-hydrogenase genes in the reactor. Using a molar balance, it was estimated that more than 30% of the acetic production can be due to the homoacetogenesis pathway, although genes from homoacetogenic microorganisms were detected at a very low concentration. The different effects of enhancement and inhibition of hydrogen production by the lactic acid bacteria and their high abundance variation could explain the instability of hydrogen production in this reactor.
Adaptive thermal control for PEMFC systems with guaranteed performance ☆ Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Lianghui Huang, Jian Chen, Zhiyang Liu, Mohamed Becherif
Proton exchange membrane fuel cell (PEMFC) s are faced with dynamical load scenario in practical applications, and the resulting temperature variation will decrease the performance and consequently shorten the fuel cell lifetime. To address this problem, a control strategy for regulating the stack temperature is proposed in this paper. Firstly, a thermal management-oriented dynamic model of a water-cooled PEMFC system is built to facilitate the control design. Secondly, considering that the stack temperature should be maintained in a certain range regardless of the dynamical changing current demand, a Barrier Lyapunov function is employed to construct a feedback error of the stack temperature. Thirdly, a set of adaptation laws is designed to estimate the unknown parameters related to the gas flow rates in the flow fields. Particularly, a dynamic inversion tracking methodology is applied to design the non-affine input. A Lyapunov method based analysis demonstrates the stability and convergence of the closed-loop properties. Simulation results are provided to show that the proposed control strategy can satisfy all the control objectives and enhance the control performance compared to the proportional-integral controlled case.
Single-step hydrothermal synthesis of WO3-MnO2 composite as an active material for all-solid-state flexible asymmetric supercapacitor Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Pragati A. Shinde, Vaibhav C. Lokhande, Amar M. Patil, Taeksoo Ji, Chandrakant D. Lokhande
In present study, new strategy is employed to build composite nanostructure and asymmetric configuration to enhance the capacitive performance of supercapacitor device. The WO3-MnO2 composite with mesoporous structure is prepared by single-step hydrothermal method and used to gain superior electrochemical performance in asymmetric configuration. A binder-free and additive-less WO3-MnO2 composite electrode exhibits high specific capacitance of 609 F g−1 at a scan rate of 5 mV s−1. The flexible asymmetric supercapacitor device with WO3-MnO2 as a positive electrode and WO3 as a negative electrode demonstrates stable operating potential window of 1.4 V with specific capacitance of 103 F g−1 at a scan rate of 5 mV s−1 and energy density of 24.13 Wh kg−1 at power density of 915 W kg−1. Furthermore, WO3-MnO2//WO3 device exhibits good cycle life with capacity retention of 95% after 2500 cycles and excellent mechanical flexibility. These results reveal the potential of WO3-MnO2 composite electrode for fabrication of high-performance supercapacitors.
Ce0.7Bi0.3O1.85-(La0.8Sr0.2)0.9MnO3-Y0.16Zr0.84O1.92 ternary cathodes for low temperature solid oxide fuel cells Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Lei Shang, Zhe Zhao, Xiaomin Zhang, Zhidong Huang, Huiying Qi, Mojie Cheng
The ternary cathodes of Ce0.7Bi0.3O1.85-(La0.8Sr0.2)0.9MnO3-Y0.16Zr0.84O1.92 (BDC-LSM-YSZ) are fabricated through infiltration for low temperature solid oxide fuel cells. The infiltrated BDC particles are 10–20 nm in size and cover on LSM and YSZ particles. The 10 wt% and 20 wt% BDC-LSM-YSZ samples show a large peak for the desorption of surface oxygen species and a large peak for the evolution of lattice oxygen, reflecting their good redox property. 0.1BDC-LSM-YSZ cell and 0.2BDC-LSM-YSZ cell give the power density at 0.6 V of 387.8 and 521.7 mWcm−2 at 600 °C, which is 3.7 and 4.9 times higher than that of LSM-YSZ cell, respectively. 0.1BDC-LSM-YSZ cell and 0.2BDC-LSM-YSZ cell exhibit low ohmic resistance and low total polarization resistance. The DRT analysis reveals that charge transfer reaction and surface diffusion are greatly accelerated on the BDC-LSM-YSZ cathodes.
Supplying hydrogen vehicles and ferries in Western Norway with locally produced hydrogen from municipal solid waste Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Maria F. Renkel, Norbert Lümmen
Gibbs free energy minimization has been used to estimate the hydrogen production potential of air gasification of the wet organic fractions of municipal solid waste available in the Bergen region in Western Norway. The aim of this work was to obtain an upper limit of the amount of hydrogen that could be produced and to estimate of the number of vehicles: passenger ferries and cars that could be supplied with an alternative fuel. The hydrogen production potential was investigated as function of waste composition, moisture content, heat loss, and carbon conversion factor. The amount of hydrogen annually available for both gasification and gasification combined with water-gas-shift-reaction was calculated for different scenarios. Up to 2700 tonne H2 per year could be produced in the best case scenario; which would, if only utilised for maritime operations, be enough to supply nine ferries and ten fast passenger boat connections in the Hordaland region in Western Norway with hydrogen.
Increased SO2 electrooxidation activity on a copper-nitrogen doped catalyst and its active sites analysis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Qing Zhao, Ming Hou, Shangfeng Jiang, Jun Ai, Limin Zheng, Zhigang Shao
It's a meaningful work to develop a highly active nonprecious SO2 electrooxidation catalyst, replacing the Pt-based ones. Here, a novel Cu-N doped carbon-based catalyst is synthesized by pyrolyzing the imidazole chelated copper ions on the chitosan modified carbon BP2000. During the preparation, metallic Cu is developed and encapsulated in the carbon lattices, and transformed into the CuNx structures on the catalyst surface, simultaneously. Metallic Cu plays significant role in the doping and developing of active sites, which have vital effects on the catalysis activity. The prereduction of Cu2+ by NaBH4 during the preparation of Doping(I)-Cu@N-C makes great contribution to the development of metallic Cu, which highly dispersive anchor in the carbon lattices. This as-synthesized Doping(I) -Cu@N-C catalyst exhibits excellent SO2 electrooxidation activity. Its SO2 oxidation currents are remarkably increased with the elevation of applied potentials, and the oxidation performances prominently surpass the commercial Pt/C, when the potential is above 0.822 V. The peak SO2 oxidation current (ip) of Doping(I)-Cu@N-C is 7.17 mA cm−2 @ 0.684 V, much higher than the 3.03 mA cm−2@ 0.584 V of Pt/C with the same mass loading. In the chronoamperometry tests under 1.2 V, the terminal oxidation current of Doping(I)-Cu@N-C was 1.74 times as high as that of Pt/C, indicating that this prepared catalyst also displays much better SO2 electrooxidation activity than Pt/C under constant applied potentials.
Polydopamine-coated halloysite nanotubes supported AgPd nanoalloy: An efficient catalyst for hydrolysis of ammonia borane Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Yang Liu, Huijuan Guan, Jun Zhang, Yafei Zhao, Jing-He Yang, Bing Zhang
Ni/MgOAl2O3 catalyst derived from modified [Ni,Mg,Al]-LDH with NaOH for CO2 reforming of methane Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Lijun Jin, Bingxue Ma, Shun Zhao, Xu He, Yang Li, Haoquan Hu, Ze Lei
[Ni,Mg,Al]-layered double hydroxide (LDH) was modified with NaOH solution to prepare the LDH-derived Ni/MgO<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Al2O3 catalyst and characterized by X-ray diffraction, inductively coupled plasma optical emission spectrometer, scanning electron microscope, transmission electron microscopy, temperature programmed desorption of CO2 or NH3, N2 adsorption, and thermogravimetry analysis, respectively. The resultant Ni/MgO<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Al2O3 catalysts were used for CO2 reforming of CH4. The results showed that the concentration of NaOH solution has an obvious effect on the structure of LDH and catalytic performances of the resultant nickel-based catalysts. Aluminum species in LDH was partly dissolved with increasing NaOH solution concentration, resulting in the increase of [M2+/M3+] molar ratio and the interlayer spacing of modified LDHs. The surface area and pore volume, especially mesoporous surface area and pore volume, were improved compared with parent [Ni,Mg,Al]-LDH, and the catalytic activity of the resultant Ni/MgO<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Al2O3 catalyst in CO2 reforming of CH4 was enhanced. NaOH concentration has a slight influence on CO2 conversion and stability of the resultant Ni/MgO<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Al2O3 catalyst. The Ni/MgO<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Al2O3 prepared from the modified [Ni,Mg,Al]-LDH with 0.1 mol/L NaOH exhibits the best stability and anti-coke deposit ability. CH4 and CO2 conversions retain at about 91% and 96%, respectively, along with a H2/CO ratio of about 0.90 after reaction of 28 h. High CO2/CH4 molar ratio can improve catalytic stability, resistance to coke deposit and Ni sintering of the catalyst.
Effective factors improving catalyst layers of PEM fuel cell Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Gokce S. Avcioglu, Berker Ficicilar, Inci Eroglu
Cathode catalyst layer has an important role on water management across the membrane electrode assembly (MEA). Effect of Pt percentage in commercial catalyst and Pt loading from the viewpoint of activity and water management on performance was investigated. Physical and electrochemical characteristics of conventional and hydrophobic catalyst layers were compared. Performance results revealed that power density of conventional catalyst layers (CLs) increased from 0.28 to 0.64 W/cm2 at 0.45 V with the increase in Pt amount in commercial catalyst from 20% to 70% Pt/C for H2/Air feed. In the case of H2/O2 feed, power density of CLs increased from 0.64 to 1.29 W/cm2 at 0.45 V for conventional catalyst layers prepared with Tanaka. Increasing Pt load from 0.4 to 1.2 mg/cm2, improved kinetic activity at low current density region in both feeding conditions. Scattering electron microscopy (SEM) images revealed that thickness of the catalyst layers (CLs) increases by increasing Pt load. Electrochemical impedance spectroscopy (EIS) results revealed that thinner CLs have lower charge transfer resistance than thicker CLs. Inclusion of 30 wt % Polytetrafluoroethylene (PTFE) nanoparticles in catalyst ink enhanced cell performance for the electrodes manufactured with 20% Pt/C at higher current densities. However, in the case of 70% Pt/C, performance enhancement was not observed. Cyclic voltammetry (CV) results revealed that 20% Pt/C had higher (77 m2/g) electrochemical surface area (ESA) than 70% Pt/C (65 m2/g). In terms of hydrophobic powders, ESA of 30PTFE prepared with 70% Pt/C was higher than 30PTFE prepared with 20 %Pt/C. X-Ray Diffractometer (XRD) results showed that diameter of Pt particles of 20% Pt/C was 2.5 nm, whereas, it was 3.5 nm for 70% Pt/C, which confirms CV results. Nitrogen physisorption results revealed that primary pores of hydrophobic catalyst powder prepared with 70% Pt/C was almost filled (99%) with Nafion and PTFE.
The vibration characteristics of drillstring with positive displacement motor in compound drilling Part1: Dynamical modelling and monitoring validation Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Guangjian Dong, Ping Chen
The storage of hydrogen energy is one of the key difficulties in the efficient use of hydrogen. The most important thing for different storage methods is to establish the aisles of the hydrogen to storage space, and efficiently drill a few high-quality well holes. Compound drilling is one of the alternative technologies. However, the bit-rock interaction and the drill string-borehole interaction make the movement of bottom hold assembly more complex and increase the difficulty of well trajectory control. The vibration characteristics of drill string during compound drilling are not clear. The numerical simulation model of drill string with positive displacement motor is established by considering the bit-rock interaction, the rock failure behavior, the drill string-borehole interaction and the drill string structural. The mechanical parameters of shale for the numerical model are measured by wave velocities method. The simulation model is verified by the measuring and motoring data of axial force in the field. The rock element damage failure rate of compound drilling is greater than conventional drilling. The axial force and torque of bit of drill string in compound drilling is greater than that in the conventional drilling. The drill string is in contact with the wellbore in a more complicated way during compound drilling. The research results are benefit for optimal design of borehole quality.
Kinetics study for sodium transformation in supercritical water gasification of Zhundong coal Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Deming Zhang, Liejin Guo, Jiuyun Zhao, Hui Jin, Wen Cao, Runyu Wang, Wenwen Wei, Jia Chen
Zhundong coal (ZDC) has attracted much attention due to its high alkali metal content which can lead to a series of problems such as furnace slagging and ash fouling. Supercritical water gasification (SCWG) become a better choice for ZDC coal utilization because of its unique chemical and physical properties. The transformation mechanism of alkali metals during SCWG process was different from conventional ways of coal utilization. Systematic research about it could hardly be found. In this study, ZDC was used to explore sodium transformation mechanism and kinetics during supercritical water gasification under typical conditions. We got four kinds of sodium including the water-soluble fraction (L1), the carboxylic matrix-associated fraction (L2), the macromolecular organic group-associated fraction (L3), and the inorganic silicate mineral fraction (L4) through sequential extraction method after SCWG. A reaction pathway of sodium transformation in supercritical water gasification was proposed. A quantitative kinetic model for describing sodium transformation mechanism was developed. Finally, it was found that, L1 played an important role in catalytic process and mineral in coal weaken the catalytic process by combining with L1. L2 and L3 served as the two important intermediate products in the coal gasification, which explained the catalytic mechanism of sodium. L3 showed better reactivity. Sodium finally tended to deposit in the form of NaSiAlO4 (L4) which was stable and environmentally friendly. All of these could provide basis for high-efficiency utilization of ZDC and the design of a reactor.
The importance of OH− transport through anion exchange membrane in microbial electrolysis cells Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Yaoli Ye, Bruce E. Logan
In two-chamber microbial electrolysis cells (MECs) with anion exchange membranes (AEMs), a phosphate buffer solution (PBS) is typically used to avoid increases in catholyte pH as Nernst equation calculations indicate that high pHs adversely impact electrochemical performance. However, ion transport between the chambers will also impact performance, which is a factor not included in those calculations. To separate the impacts of pH and ion transport on MEC performance, a high molecular weight polymer buffer (PoB), which was retained in the catholyte due to its low AEM transport and cationic charge, was compared to PBS in MECs and abiotic electrochemical half cells (EHCs). In MECs, catholyte pH control was less important than ion transport. MEC tests using the PoB catholyte, which had a higher buffer capacity and thus maintained a lower catholye pH (<8), resulted in a 50% lower hydrogen production rate (HPR) than that obtained using PBS (HPR = 0.7 m3-H2 m−3 d−1) where the catholyte rapidly increased to pH = 12. The main reason for the decreased performance using PoB was a lack of hydroxide ion transfer into the anolyte to balance pH. The anolyte pH in MECs rapidly decreased to 5.8 due to a lack of hydroxide ion transport, which inhibited current generation by the anode, whereas the pH was maintained at 6.8 using PBS. In abiotic tests in ECHs, where the cathode potential was set at −1.2 V, the HPR was 133% higher using PoB than PBS due to catholyte pH control, as the anolyte pH was not a factor in the performance. These results show that maintaining charge transfer to control anolyte pH is more important than obtaining a more neutral pH catholyte.
Hydrogen generation by hydrolysis of Mg-Mg2Si composite and enhanced kinetics performance from introducing of MgCl2 and Si Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Zhenhua Tan, Liuzhang Ouyang, Jiangwen Liu, Hui Wang, Huaiyu Shao, Min Zhu
This paper reported the performance and mechanism of hydrogen generation via hydrolysis of ball-milled Mg-Mg2Si composite (5.3 wt % Si-94.7 wt % Mg) in deionized water and in MgCl2 solution. The results showed that the obtained Mg-Mg2Si composite presented relatively higher hydrogen generation performance than pure magnesium. Adoption of 0.5 M MgCl2 solution to replace deionized water sufficiently and vastly enhanced the hydrolysis properties of the Mg-Mg2Si composite. The composite in 0.5 M MgCl2 solution generated 445 mL/g hydrogen in 5 min, 688 mL/g hydrogen in 10 min and 889 mL/g hydrogen (conversion rate 99%) in 40 min at 328 K. This remarkable improvement is due to that the addition of Si element in the composite and the introduction of MgCl2 in solution, as well as the special preparation process of the materials, could decrease the formation of continuous magnesium hydroxide passive layer on the particle surface, directly or indirectly. Moreover, the apparent activation energies for composite hydrolysis in deionized water, in 0.5 and 2.0 M MgCl2 solution were calculated to be 30.1 ± 0.6, 9.5 ± 0.1 and 3.7 ± 0.2 kJ/mol, respectively. This work demonstrates that the hydrogen generation system based on low-cost and high-performance Mg-Mg2Si composite is very applicable and promising; and it may open a new avenue for onsite hydrogen supply.
Experimental study of direct solar photocatalytic water splitting for hydrogen production under natural circulation conditions Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-11 Fei Cao, Huan Liu, Qingyu Wei, Liang Zhao, Liejin Guo
Photocatalytic water splitting for hydrogen production provides a promising route for the future hydrogen economy, being operational in the visible light domain with a potential use of solar radiation. An outdoor pilot demonstration of CPC-based photoreactors has been designed, installed and tested at the State Key Laboratory of Multiphase Flow in Power Engineering to assess its effectiveness in solar photocatalytic hydrogen production. Nine sets of CPC-based photoreactors, each of which is 3.6 m2 in area and 23 L in volume, are connected, controlled and operated in parallel. The high efficiency photocatalyst (Cd1-xZnxS), low concentration sacrifice agents (Na2S and Na2SO3) and deionized water are the raw materials of the pilot system. Two operation models, viz. the natural circulation model and the gas disturbance model, are proposed considering the expense and the efficiency. From our observations, the slurry temperature inside the tubes rises by 20–30 °C from the ambient. The slurry velocity can reach 1.2 m/s in the gas disturbance model, but is as low as 3.5 cm/s in the natural circulation model. The average hydrogen productivity is 184.30 mL/min and accumulated to be 10.321 L/h in the natural circulation model, with the average solar radiation, photocatalyst concentration and sacrifice agents' concentration being 803.8 W/m2, 2.77 g/L and 0.1 mol/L, respectively.
Economic viability and production capacity of wind generated renewable hydrogen Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 M. Mohsin, A.K. Rasheed, R. Saidur
Generally, wind to power conversion is calculated by assuming the quality of wind as measured with a Weibull probability distribution at wind speed during power generation. We build on this method by modifying the Weibull distributions to reflect the actual range of wind speeds and wind energy density. This was combined with log law that modifies wind speed based on the height from the ground, to derive the wind power potential at windy sites. The study also provides the Levelized cost of renewable energy and hydrogen conversion capacity at the proposed sites. We have also electrolyzed the wind-generated electricity to measure the production capacity of renewable hydrogen. We found that all the sites considered are commercially viable for hydrogen production from wind-generated electricity. Wind generated electricity cost varies from $0.0844 to $0.0864 kW h, and the supply cost of renewable hydrogen is $5.30 to $ 5.80/kg-H2. Based on the findings, we propose a policy on renewable hydrogen fueled vehicles so that the consumption of fossil fuels could be reduced. This paper shall serve as a complete feasibility study on renewable hydrogen production and utilization.
Hydrogen storage comparison of M doped vanadium oxide nanotubes (M = Mo, Zr and W): A molecular simulation study Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 A. Salimian, S. Ketabi, H.R. Aghabozorg
Zr, Mo and W doped Vanadium oxide nanotube were considered as remarkable materials for hydrogen storage applications. Monte Carlo molecular simulation was performed to study the adsorption behavior of hydrogen molecules on Vanadium oxide nanotubes (VONTs). The effects of temperature, pressure and mole percent of hydrogen on adsorption capacity of VONTs were investigated to provide deep insight of adsorption behavior. The results represented that hydrogen adsorption is an increasing function of pressure and at about 50 MPa all three metal doped VONT has maximum hydrogen capacity. At 5 MPa and room temperature, the hydrogen capacities of Mo, W and Zr doped VONTs were 1.39, 0.88 and 1.43 w% respectively. With temperature increment up to room temperature, more reduction in initial hydrogen capacity were observed in Mo and Zr doped VONTs. Evaluating hydrogen adsorption of Zr doped VONT from pure and hydrogen /nitrogen mixtures at 300 K indicated that under 2 Mpa, modifications in adsorption capacities were insignificant after N2 addition to the environment. Therefore, Zr doped VONT in hydrogen /nitrogen mixture environment can act as a capable adsorbent for Hydrogen storage system in comparison with Mo and W doped VONTs.
Interface resolving two-phase flow simulations in gas channels relevant for polymer electrolyte fuel cells using the volume of fluid approach Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 M. Andersson, S.B. Beale, U. Reimer, W. Lehnert, D. Stolten
Hydrogen storage studies in Pd/Ti/Mg films Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 G.L.N. Reddy, Sanjiv Kumar
This paper describes investigations (a) on the efficacy of Ti layer as a barrier against the intermixing of Pd and Mg in Pd/Ti/Mg films and (b) the hydrogen storage characteristics of the tri-layered films and the related bulk composites. The Mg film was prepared by resistive evaporation while the Pd and Ti films were deposited by e-beam evaporation. The analysis by Rutherford backscattering spectrometry (RBS) and glancing-incidence X-ray diffraction (GI-XRD) of the Pd/Ti/Mg/Si(substrate) films annealed in vacuum in 348–573 K temperature range revealed that Ti effectively prevents the intermixing of Pd and Mg up to ∼523 K. However, mixing across Pd/Ti, Ti/Mg and Mg/Si interfaces commences around 523 K that progresses with the temperature of annealing though Pd<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Mg phases are not formed even at 573 K. The as-deposited Pd/Ti/Mg films are hydrogenated to ∼7 wt % (62 at%) at 323–423 K at 0.15 MPa hydrogen pressure and dehydrogenated completely at ∼ 473 K. The extent of (de)hydrogenation of the films was determined non-destructively by the 1H(19F,αγ)16O nuclear reaction. The powder composites derived from the films, on the other hand, reversibly stored ∼2.2 wt% hydrogen up to 18 cycles in 323–473 K temperature range. The superior cyclic stability is attributed to the inhibition of mixing between Pd and Mg and, as a result, the formation of Pd<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">Mg inter-metallics by titanium.
Electrocatalysis of hydrogen evolution reaction on tri-metallic Rh@Pd/Pt(poly) electrode Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 M. Smiljanić, Z. Rakočević, S. Štrbac
Hydrogen evolution reaction (HER) was investigated in alkaline solution on tri-metallic Rh@Pd/Pt(poly) electrode, prepared by spontaneous deposition of Rh on top of Pd/Pt(poly) electrode with intermediate Pd coverage of 35%. Characterization of tri-metallic catalyst was performed by electrochemical methods of cyclic voltammetry and CO stripping voltammetry, while its activity for HER was tested by linear sweep voltammetry in 0.1 M NaOH. Rh@Pd/Pt(poly) catalyst has shown superior catalytic activity for HER with respect to initial Pt(poly) and both corresponding bimetallic Pd/Pt(poly) and Rh/Pt(poly) electrodes. This was explained by a strong synergistic electronic interaction between three metals in close contact induced at a number of different active sites across the surface of tri-metallic catalyst, which results with lowering of the binding energy for the adsorption of H intermediate species.
Two-tier pressure consolidation operation method for hydrogen refueling station cost reduction Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Krishna Reddi, Amgad Elgowainy, Neha Rustagi, Erika Gupta
An operation strategy known as two-tier “pressure consolidation” of delivered tube-trailers (or equivalent supply storage) has been developed to maximize the throughput at gaseous hydrogen refueling stations (HRSs) for fuel cell electric vehicles (FCEVs). The high capital costs of HRSs and the consequent high investment risk are deterring growth of the infrastructure needed to promote the deployment of FCEVs. Stations supplied by gaseous hydrogen will be necessary for FCEV deployment in both the near and long term. The two-tier pressure consolidation method enhances gaseous HRSs in the following ways: (1) reduces the capital cost compared with conventional stations, as well as those operating according to the original pressure consolidation approach described by Elgowainy et al. (2014) , (2) minimizes pressure cycling of HRS supply storage relative to the original pressure consolidation approach; and (3) increases use of the station's supply storage (or delivered tube-trailers) while maintaining higher state-of-charge vehicle fills.
An experimental and numerical study on the combustion and flame characteristics of hydrogen in intersecting slot burners Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Mehrdad Kiani, Ehsan Houshfar, Mehdi Ashjaee
In the present study, two impinging slot jets of hydrogen gas at different angles and distances are investigated experimentally using the Mach-Zehnder interferometry. The obtained temperatures from the interferometry method were validated against the thermocouple measurements. The generated temperature field is studied using infinite fringe interferometry. Slot burners with high length-to-width ratio are utilized to ensure producing a uniform 2D flow. The slot burners' angle and the distance between the burners are varied from 60 to 100° and 10 mm–25 mm in the increment of 20° and 5 mm, respectively. The Reynolds number is varied from 70 to 150, and the equivalence ratio is changed from 0.8 to 2.5. The results indicated that the Reynolds number does not have a considerable effect on increasing the maximum temperature, while, it has a significant influence on the flame structure. The equivalence ratio has a substantial effect on both maximum temperature and flame structure. Also, the variations in angle of burners have a considerable effect on the flame stability. Furthermore, the distance of burners strongly affects the maximum flame temperature and the flame structure. It was observed that by increasing the burners distance, the domain of maximum temperature is descended. The results from numerical modeling were also validated with experiments. The effect of temperature on the NOx emissions was clearly shown in the CFD simulations.
Direct formation of dendritic Ag catalyst on a gas diffusion layer for electrochemical CO2 reduction to CO and H2 Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Yu Seok Ham, Myung Jun Kim, Taeho Lim, Dong-Kwon Kim, Soo-Kil Kim, Jae Jeong Kim
DFT study of the enhancement on hydrogen production by alkaline catalyzed water gas shift reaction in supercritical water Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Runyu Wang, Liejin Guo, Hui Jin, Libo Lu, Lei Yi, Deming Zhang, Jia Chen
Supercritical water gasification (SCWG) is hopefully to be an acceptable choice for hydrogen production, the hydroxide ion assisted water gas shift reaction (WGSR) has been regarded as the most important reaction to generate hydrogen during the process. However, the principle of practical OH− catalyzed reaction is not possible to acquire by experiments. Thus, density functional theory (DFT) is utilized to investigate the reaction mechanism theoretically in this work. Through first principle calculations, every species and energy barrier for elementary steps are achieved, and formate ion is determined as the important intermediate. Besides, HCOO− + H2O → HCO3− + H2 is the dominant path to generate hydrogen, as well as the rate-determining step with 47.94 kcal/mol energy barrier. Furthermore, the reaction rate constant is calculated to be kcatalytic(s−1) = 2.34 × 1012exp(−1.80 × 105/RT) using transition state theory with Wigner transmission coefficient (TST/w). Lastly, supercritical water condition is demonstrated to be a favored media for WGSR, because it may dissociate, dissolve or hydrolyze more hydroxide anion than conventional steam. The results are expected to benefit the control of reaction process and the design of SCWG reactor.
Maximizing the production of hydrogen and carbon nanotubes: Effect of Ni and reaction temperature Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Syedvali Pinjari, Madan Kumar Kumaravelan, Venkat Chalapathirao Peddy, Sriganesh Gandham, Jagannadharao Patruni, Sridevi Velluru, Pramod Kumar
RETRACTED: Feedback controller input design for ignition of deuterium–tritium in NSTX tokamak Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2016-07-21 A. Naghidokht, A. Salar Elahi, M. Ghoranneviss, R. Khodabakhsh
This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the Editor-in-Chief.After a thorough investigation, the Editor has concluded that the acceptance of this article was based upon the positive advice of at least one illegitimate reviewer report. The report was submitted from an email account which was provided to the journal as a suggested reviewer during the submission of the article. Although purportedly a real reviewer account, the Editor has concluded that this was not of an appropriate, independent reviewer.This manipulation of the peer-review process represents a clear violation of the fundamentals of peer review, our publishing policies, and publishing ethics standards. Apologies are offered to the reviewers whose identities were assumed and to the readers of the journal that this deception was not detected during the submission process.In addition, no reason has been provided for the addition of the author names A. Naghidokht, A. Salar Elahi, M. Ghoranneviss and R. Khodabakhsh to the authorship of the revised article.
Toward generalized models for estimating molecular weights and acentric factors of pure chemical compounds Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Abdolhossein Hemmati-Sarapardeh, Forough Ameli, Amir Varamesh, Shahaboddin Shamshirband, Amir H. Mohammadi, Bahram Dabir
In this work, four prompt and robust techniques have been used to introduce new generalized models for estimation of the physical properties of pure substances, including molecular weight and acentric factor. These methods were developed based on radial basis function (RBF) neural networks, group method of data handling (GMDH), multilayer perceptron (MLP), and least square support vector machine (LSSVM) techniques. Models were introduced based on a set of experimental data including 563 pure compounds that were collected from available literature. Input parameters for estimation of molecular weight were considered as specific gravity and normal boiling point. Critical temperature, critical pressure and normal boiling point were selected as inputs for estimation of the acentric factor. Statistical and graphical error analyses normal boiling point revealed that all of the developed models are accurate. The designed RBF models give the most accurate results with an AAPRE of 5.98% and 1.92% for molecular weight and acentric factor, respectively. The developed GMDH models are in the form of simple correlations, which can be used easily in hand calculation problems without any need to computers. Comparison of the developed models with the available methods showed that all of the developed models are more accurate than the existing methods. Using the relevancy factor, the impact of each input parameter on the output results was determined. Additionally, to find out the applicability region of the developed models, and to demonstrate the reliability of the models, the Leverage method has been used. There are few data out of the applicability domain of the proposed models. All the statistical and graphical resolutions, demonstrate the reliability of the developed models in estimating the molecular weight and acentric factor.
Grand canonical Monte Carlo and molecular dynamics simulations of the structural properties, diffusion and adsorption of hydrogen molecules through poly(benzimidazoles)/nanoparticle oxides composites Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-10 Abdollah Khosravanian, Mostafa Dehghani, Mahdieh Pazirofteh, Morteza Asghari, Amir H. Mohammadi, Davood Shahsavari
Comprehensive structural/molecular simulations have been undertaken to study the poly(benzimidazoles) (PBI) membrane combined with four different nano-oxide materials (ZnO, Al2O3, SiO2 and TiO2) for purification and production of hydrogen from natural gases. Composite membranes were built with different amounts of nano-oxide materials to investigate the influence of nano-oxide content on the PBI membrane performance. Several structural characterizations such as FFV, WAXD and also a thermal one (glass transition temperature) were done to study the structural properties of all simulated membrane cells. Moreover, MSD and adsorption isotherms tasks were used to estimate the diffusivity and solubility of hydrogen molecules through the latter mixed matrix membranes (MMMs), respectively. Permeability and permselectivity of H2 penetrate molecules were also carefully calculated using the aforementioned penetrating factors (diffusivity and solubility). Results show a significant improvement in structural and transport properties by increasing the nanomaterials content, which could be due to the growth of penetration pathways through the membranes. Furthermore, membranes with SiO2 yield the best results compared to other three nano-oxide fillers. H2 gas yields the best results that help the storage and separation of this precious gas from other gas molecules, which present in natural gases. Compared to the previous studies and literature results, the current results are accurate and reliable to describe the structural and transport properties of PBI/nano-oxides composites.
The detrimental effect of hydrogen at dislocations on the hydrogen embrittlement susceptibility of Fe-C-X alloys: An experimental proof of the HELP mechanism Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-09 T. Depover, K. Verbeken
The hydrogen trapping ability of 15 Fe-C-X alloys is compared in this work. Five types of carbides, i.e. Ti, Cr, Mo, W and V based carbides, and their effect on the hydrogen embrittlement susceptibility is considered while three carbon contents are prepared for each carbide former. Two conditions are compared for each alloy to evaluate the hydrogen/material interaction: an as quenched and quenched and tempered condition in which carbides are introduced. Next to the material characterization, also the interaction of hydrogen with the materials is completely elaborated. At first, in-situ tensile tests are done to determine the hydrogen induced ductility loss. To interpret the obtained degrees of hydrogen embrittlement, hot/melt extraction is done to determine the hydrogen content, whereas thermal desorption spectroscopy is performed to assess the hydrogen trapping capacity of the tempered induced precipitates and the different other potentially hydrogen trapping microstructural features. These measurements are done after hydrogen pre-charging till saturation. The tempered induced TiC and V4C3 are capable of trapping a significant amount of hydrogen, while the Mo2C and Cr23C6 particles only trap a limited amount of hydrogen. The W2C precipitates, however, are not able to trap hydrogen. The size and coherency of the carbides are considered to be the main factor determining their trapping ability. The degree of hydrogen embrittlement is correlated with the hydrogen present in the alloys. Three amounts of hydrogen were determined by the strength by which they were trapped by combining the different hydrogen characterization techniques, i.e. total, diffusible and mobile hydrogen. It was confirmed that hydrogen trapped by dislocations plays a determinant role. This further confirms the importance of an enhanced dislocation mobility in the presence of hydrogen, as described in the HELP mechanism.
Assessment of sugarcane bagasse gasification in supercritical water for hydrogen production Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-08 Wen Cao, Liejin Guo, Xuecheng Yan, Deming Zhang, Xiangdong Yao
Sugarcane bagasse is one of the major resources of agricultural biomass waste in the world. In this work, supercritical water gasification characteristics of sugarcane bagasse were investigated. The effect of temperature (600–750 °C), concentration (3–12 wt%), residence time (5–20 min) and catalysts (Raney-Ni, K2CO3 and Na2CO3) on bagasse gasification were studied. A kinetic study on the non-catalytic and Na2CO3 catalytic bagasse gasification was conducted to describe the kinetic information of the bagasse gasification reaction. The results showed that a higher reaction temperature, a lower bagasse concentration and a longer residence time could favor the gasification of bagasse, leading to a higher hydrogen yield. Bagasse was nearly completely gasified at 750 °C without using any catalyst and the carbon gasification efficiency could reach up to 96.28%. The addition of employed catalysts remarkably promoted the bagasse gasification reactivity. The maximum hydrogen yield (35.3 mol/kg) was achieved at 650 °C with the Na2CO3 loading of 20 wt%. The experimental data fitted well with a homogeneous model based on a Pseudo-first-order reaction hypothesis. The kinetic study showed that Na2CO3 catalyst could lower the activation energy Ea of bagasse gasification from 117.88 kJ/mol to 78.25 kJ/mol.
Experimental investigation on the influence of the pyrolysis operating parameters upon the char reaction activity in supercritical water gasification Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-08 Hui Jin, Cui Wang, Chao Fan, Liejin Guo, Changqing Cao, Wen Cao
Supercritical water gasification of coal is a clean and efficient method for coal utilization which can convert coal into H2 and CO2. In order to further reduce costs, a novel two-step cascade utilization method was proposed in this study: conducting traditional pyrolysis first and then gasifying the pyrolysis char in supercritical water. The influences of different pyrolysis operating parameters on gaseous products and char gasification in supercritical water were investigated. Quartz tube reactors were used to ensure the complete collection of gaseous products in pyrolysis process. The experimental results showed that both carbon and hydrogen conversion efficiency increased with temperature, and the increasing trend became not obvious after reaction for 5 min. The thermo-gravimetric curves showed that volatilization removal process was completed at the pyrolysis time of 5 min and higher pyrolysis temperatures were beneficial to the subsequent gasification process. The result also showed that residual weight was 15%–20% of the initial weight. Hydroxyl radicals kept stable during pyrolysis process with the absorption peak intensity increasing first and then decreasing, and mineral substance disintegrated gradually as time increased. As pyrolysis temperature increased, the peak of C<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">C double bonds decreased, turning into stable functional groups and carbonyl group increased. Dispersive pores occurred at the surface of coal as residence time increased with particle size decreasing, specific surface area and reactivity increasing. The results might be used for the design of a cascade utilization system based on coal gasification in supercritical water.
Carbon-supported small Rh nanoparticles prepared with sodium citrate: Toward high catalytic activity for hydrogen evolution from ammonia borane hydrolysis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Jiaqin Chen, Min Hu, Mei Ming, Caili Xu, Yi Wang, Yun Zhang, Jiangtao Wu, Daojiang Gao, Jian Bi, Guangyin Fan
Hydrogen generation from the hydrolysis of ammonia borane (AB) over heterogeneous catalysts is essential for practical applications. Herein, efficient hydrogen evolution from AB hydrolysis over the carbon-supported Rh nanoparticles synthesized with sodium citrate (Rh/C-SC) was achieved at 25 °C. The turnover frequency value of Rh/C-SC was 336 mol H2 (molRh min)−1, whereas that of Rh/C catalyst only yielded a value of 134 mol H2 (molRh min)−1. The improvement of the catalytic performance of Rh/C-SC catalyst could be attributed to the small Rh particles with highly active surface areas, which were prepared by using sodium citrate as the stabilizing agent. This result indicates that sodium citrate can be applied as a useful stabilizing agent for synthesizing active metal nanoparticles, thus highly promoting the practical application of AB system for fuel cells.
Hydrogen production from sulphide wastewater using Ce3+–TiO2 photocatalysis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 J. Bharatvaj, V. Preethi, S. Kanmani
Cerium (Ce3+) doped TiO2 powder was synthesized by a sol-gel method and characterized by Transmission Electron Microscope (TEM), X-ray Diffraction (XRD), UV–Vis Diffuse Reflectance Spectroscopy (UV-DRS), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The Ce3+ doping strongly reduced the band gap of the TiO2 from 3.2 eV (UV) to 2.7 eV (visible region). The photocatalytic activity of Ce3+ doped TiO2 catalysts was evaluated by hydrogen production from sulphide wastewater under visible light illumination. The photocatalytic production of H2 was studied in a batch recycle tubular photocatalytic reactor. The results show that 0.4% Ce3+–TiO2 suspended in 500 mL of simulated sulphide wastewater irradiated at 150 W visible lamp produced maximum H2 of 6789 μmol h−1. It was noticed that the Ce3+ doped TiO2 performs well than Nano TiO2 and P25 TiO2 photocatalysts.
Hierarchical Co3O4 decorated PPy nanocasting core-shell nanospheres as a high performance electrocatalysts for methanol oxidation Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Diab Khalafallah, Othman Y. Alothman, H. Fouad, Khalil Abdelrazek Khalil
Hydrogen adsorption properties of Ag decorated TiO2 nanomaterials Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Saravanan Rajendran, Tuan K.A. Hoang, Rabah Boukherroub, D.E. Diaz-Droguett, F. Gracia, M.A. Gracia-Pinilla, A. Akbari-Fakhrabadi, Vinod Kumar Gupta
Hydrogen production using methane: Techno-economics of decarbonizing fuels and chemicals Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Brett Parkinson, Mojgan Tabatabaei, David C. Upham, Benjamin Ballinger, Chris Greig, Simon Smart, Eric McFarland
Effects of content of hydrogen on the characteristics of co-flow laminar diffusion flame of hydrogen/nitrogen mixture in various flow conditions Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Tananop Piemsinlapakunchon, Manosh C. Paul
Effect of content of hydrogen (H2) in fuel stream, mole fraction of H2(XH2) ( X H 2 ) in fuel composition, and velocity of fuel and co-flow air (Vavg) ( V a v g ) on the flame characteristics of a co-flow H2/N2 laminar diffusion flame is investigated in this paper. Co-flow burner of Toro et al.  is used as a model geometry in which the governing conservation transport equations for mass, momentum, energy, and species are numerically solved in a segregated manner with finite rate chemistry. GRI3 reaction mechanisms are selected along with the weight sum of grey gas radiation (WSGG) and Warnatz thermo-diffusion models. Reliability of the newly generated CFD (computational fluid dynamics) model is initially examined and validated with the experimental results of Toro et al. . Then, the method of investigation is focused on a total of 12 flames with XH2 X H 2 varying between 0.25 and 1, and Vavg V a v g between 0.25 and 1 ms−1. Increase of flame size, flame temperature, chemistry heat release, and NOx emission formation resulted are affected by the escalation of either XH2 X H 2 or Vavg V a v g . Significant effect on the flame temperature and NOx emission are obtained from a higher XH2 X H 2 in fuel whereas the flame size and heat release are the result of increasing Vavg V a v g . Along with this finding, the role of N2 and its higher content reducing the flame temperature and NOx emission are presented.
Exergy analysis and multiobjective optimization of a biomass gasification based multigeneration system Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Halimeh Rashidi, Jamshid Khorshidi
Biomass gasification is a process of converting biomass to a combustible gas suitable for use in boilers, engines and turbines to produce combined cooling, heat and power. This paper presents a detailed model of a biomass gasification system and designs a multigeneration energy system which uses the biomass gasification process for generating combined cooling, heat and electricity. Energy and exergy analyses are first applied to evaluate the performance of the designed system. Next, minimizing total cost rate and maximizing exergy efficiency of the system are considered as two objective functions and a multiobjective optimization approach based on differential evolution algorithm and local unimodal sampling technique is developed to calculate the optimal values of the multigeneration system parameters. A parametric study is then carried out and Pareto front curve is used to determine the trend of objective functions and assess the performance of the system. Furthermore, a sensitivity analysis is employed to evaluate effects of design parameters on the objective functions. Simulation results are compared with two other multiobjective optimization algorithms and effectiveness of the proposed method is verified using various performance indicators.
Modeling hydrogen production in a catalytic-inert packed bed reactor by rich combustion of heavy fuel oil Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 J. Gómez, J.P. Mmbaga, R.E. Hayes, M. Toledo, F. Gracia
This work presents simulation results for the production of hydrogen by the rich combustion of heavy fuel oil in a dual zone packed bed reactor. The first zone provides catalytic-thermal cracking of the fuel and is followed by a second zone for partial oxidation reforming of the cracked products. The kinetic model for the heavy fuel oil reactions in the catalytic zone uses decalin as a model compound. The partial oxidation reforming zone uses model compounds for the product groups formed from decalin cracking, and uncracked decalin. The hybrid reactor model is compared to results from a model of an inert (non-catalytic) porous media reactor. The work considers equivalence ratios from 1 to 2, filtration velocities between 15.0 and 65.5 cm/s, heat loss from 10 to 108% and particle diameter between 3 and 7 mm, and evaluates their effect on conversion. The simulations with the hybrid reactor model, in slightly rich conditions (equivalence ratio = 1.3) and constant filtration velocity of 19.3 cm/s deliver maximum hydrogen production for an optimal length of the intermediate zone. Considering this optimization: the total energy conversion efficiencies improve with the increase of the equivalence ratio due to the presence of hydrocarbon species generated by the cracking process. It is observed that the hybrid reactor model makes a better use of vaporized fuel, compared to a model for an inert packed bed reactor, when the deposits of carbonaceous material in the latter exceed 7.4%.
Impacts of nano-metal oxides on hydrogen production in anaerobic digestion of palm oil mill effluent – A novel approach Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-06 Puranjan Mishra, Sveta Thakur, Durga Madhab Mahapatra, Zularisam Ab Wahid, Hong Liu, Lakhveer Singh
Hydrogen addition to tea seed oil biodiesel: Performance and emission characteristics Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-05 Hasan Serin, Şafak Yıldızhan
Compression ignition engines are the dominant tools of the modern human life especially in the field of transportation. But, the increasing problematic issues such as decreasing reserves and environmental effects of diesel fuels which is the energy source of compression ignition engines forcing researchers to investigate alternative fuels for substitution or decreasing the dependency on fossil fuels. The mostly known alternative fuel is biodiesel fuel and many researchers are investigating the possible raw materials for biodiesel production. Also, hydrogen fuel is an alternative fuel which can be used in compression ignition engines for decreasing fuel consumption and hazardous exhaust emissions by enriching the fuel. In this study, influences of hydrogen enrichment to diesel and diesel tea seed oil biodiesel blends (B10 and B20) were investigated on an unmodified compression ignition engine experimentally. In consequence of the experiments, lower torque and higher brake specific fuel consumption data were measured when the engine was fuelled diesel biodiesel blends (B10 and B20) instead of diesel fuel. Also, diesel biodiesel blends increased CO2 and NOx emissions while decreasing the CO emissions. Hydrogen enrichment (5 l/m and 10 l/m) was improved the both torque and brake specific fuel consumption for all test fuels. Furthermore, hydrogen enrichment reduced CO and CO2 emissions due to absence of carbon atoms in the chemical structure for all test fuels. Increasing flow rate of hydrogen fuel from 5 l/m to 10 l/m further improved performance measures and emitted harmful gases except NOx. The most significant drawback of the hydrogen enrichment was the increased NOx emissions.
Development and assessment of a novel solar heliostat-based multigeneration system Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-05 Rami S. El-Emam, Ibrahim Dincer
In this paper, a comprehensive study on thermodynamic analysis and assessment, through energy and exergy approaches, is conducted for a multigenerational solar based integrated energy system. The system proposed in this study is based on heliostat solar system integrated with steam turbine. The system is also integrated with seawater reverse osmosis desalination unit and absorption cooling system. The desalination unit operates with energy recovery through the utilization of Pelton turbine. The system produces cooling, heating, fresh water and hydrogen through electrolysis. It is furthermore designed to cover the demand of 4 MW electric power with the production of 1.25 kg/h of hydrogen and 90 kg/s of fresh water. The system advisor model software is applied on a case study for the solar heliostat optimization analysis.
The effects of hydrogen addition on silica aggregate growth in atmospheric-pressure, 1-D methane/air flames with hexamethyldisiloxane admixture Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-04 Peter N. Langenkamp, Howard B. Levinsky, Anatoli V. Mokhov
The effect of hydrogen addition on silica growth in burner-stabilized methane/air flames with trace amounts of hexamethyldisiloxane are reported. Profiles of the aggregates' radius of gyration RgRg and monomer radius aa versus residence time were measured by laser light scattering. Experiments were performed at equivalence ratios of 0.8, 1.0 and 1.3, with mole fractions of 0–0.4 of hydrogen in the fuel. At equal mass flux, the addition of hydrogen was found to result in decreasing RgRg and aa. However, keeping the flame temperature rather than the mass flux constant upon hydrogen addition resulted in the same measured profiles.
Comparative performance analysis of a grid connected PV system for hydrogen production using PEM water, methanol and hybrid sulfur electrolysis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-04 H. Tebibel, R. Medjebour
Mechanical activation of TiFe for hydrogen storage by cold rolling under inert atmosphere Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-04 L.E.R. Vega, D.R. Leiva, R.M. Leal Neto, W.B. Silva, R.A. Silva, T.T. Ishikawa, C.S. Kiminami, W.J. Botta
TiFe is a very interesting material for hydrogen storage in the solid state, due to its hydrogen capacity of 1.9 wt % and to the fact it can be absorb/desorb hydrogen at room temperature. However, the TiFe produced by casting does not absorb hydrogen, unless a procedure called activation is applied, which is based on a repetition of several thermal cycles. This study evaluates the effects of a mechanical activation route for the TiFe intermetallic compound, namely, cold rolling (CR) under inert atmosphere. Stoichiometric TiFe was prepared from elementary powders by arc melting. Ingot was grinded and then cold rolled for 20 and 40 passes under argon inside a glove box, with moisture and oxygen contents below 0.1 ppm. Cold rolled samples consisted of two parts: powder particles and thin cracked flakes. The results showed that mechanically activated samples by CR exhibited rapid absorption of hydrogen at room temperature, without using a thermal activation process. In general, the average storage capacity of hydrogen was 1.4 wt% H2 for the first absorption, regardless of the number of passes for both flake and powder samples.
Catalytic hydrogenation of CO2 from 600 MW supercritical coal power plant to produce methanol: A techno-economic analysis Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-04 Muhammad Asif, Xin Gao, Hongjie Lv, Xinguo Xi, Pengyu Dong
Electricity and water from renewable hydropower plant are used as input for electrolysis unit to generate hydrogen, while CO2 is captured from 600 MW supercritical coal power plant using post-combustion chemical solvent based technology. The captured CO2 and H2 generated through electrolysis are used to synthesize methanol through catalytic thermo-chemical reaction. The methanol synthesis plant is designed, modeled and simulated using commercial software Aspen Plus®. The reactor is analyzed for two widely adopted kinetic models known as Graaf model and Vanden-Bossche (VB) model to predict the methanol yield and CO2 conversion. The results show that the methanol reactor based on Graaf kinetic model produced 0.66 tonne of methanol per tonne of CO2 utilized which is higher than that of the VB kinetic model where 0.6 tonne of methanol is produced per tonne of CO2 utilized. The economic analysis reveals that 1.2 billion USD annually is required at the present cost of both H2 production and CO2 abatement to utilize continuous emission of 3.2 million tonne of CO2 annually from 600 MW supercritical coal power unit to synthesize methanol. However, sensitivity analysis indicates that methanol production becomes feasible by adopting anyone of the route such as by increasing methanol production rate, by reducing levelised cost of hydrogen production, by reducing CO2 mitigation cost or by increasing the current market selling price of methanol and oxygen.
Influence of Ag nanoparticles on state of the art MnO2 nanorods performance as an electrocatalyst for lithium air batteries Int. J. Hydrogen Energy (IF 3.582) Pub Date : 2018-01-04 Zahoor Awan, Zafar Khan Ghouri, Saud Hashmi
The need for an alternative and efficient electrocatalyst to replace Pt-based noble materials is a goal of prime importance in Li– air battery technology. In this work, novel silver nanoparticles-incorporated MnO2 nanorods as an air electrode bifunctional catalyst have been synthesized by a simple polyol method. The physical characteristics of the thus prepared materials are analyzed by X-ray diffraction (XRD), SEM, and Brunauer–Emmett–Teller (BET) techniques. These analyses confirmed the successful synthesis of 20 to 25 nm-sized different weight % Ag nanoparticles incorporated on α-MnO2 nanorods. Linear sweeping voltammetric results of Ag MnO2 showed improved ORR performance as compared to α- MnO2 nanorods in terms of the onset potential, half wave potential and limiting current. The addition of catalysts has significantly increased the discharge capacity and overall performance of the cells. The first discharge curve of 5 wt% Ag MnO2 sample reached a maximum capacity of 3500 mAhg-1 at 2.0 V with a current density of 0.1 mA cm−2 with a plateau between 2.7 and 2.6 V. Long term stability of increasing weight percentage of Ag nanoparticles on MnO2 samples is increased.
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