Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation ...Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.展开更多
Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studie...Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studied for the purpose of high pressure compression.A compact compression system has been built.Each designed small-size reactor contains seven special stainless-steel pipes.The single stage compressor can improve the hydrogen pressure from 2 up to 35 MPa with the hydrogen desorbed per unit mass of 207.8 mL/g.The two-stage compression can output hydrogen with pressure of 38 MPa steadily in whole 5.7 mol hydrogen output flow.However,its hydrogen desorbed per unit mass was only computed to 106.9 mL/g as a result of two reactors used in the cycle and the output mass of hydrogen increased less.展开更多
Rare earth-Mg-Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries.Among them,the novel AB_(4)-type superlattice structure alloy is suppos...Rare earth-Mg-Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries.Among them,the novel AB_(4)-type superlattice structure alloy is supposed to have superior cycling stability and rate capability.Yet its preparation is hindered by the crucial requirement of temperature and the special composition which is close to the other superlattice structure.Here,we prepare rare earth-Mg-Ni-based alloy and study the phase transformation of alloys to make clear the formation of AB_(4)-type phase.It is found Pr_(5)Co_(19)-type phase is converted from Ce_(5)Co_(19)-type phase and shows good stability at higher temperature compared to the Ce_(5)Co_(19)-type phase in the range of 930-970℃.Afterwards,with further 5℃increasing,AB_(4)-type superlattice structure forms at a temperature of 975℃by consuming Pr_(5)Co_(19)-type phase.In contrast with A_(5)B_(19)-type alloy,AB_(4)-type alloy has superior rate capability owing to the dominant advantages of charge transfer and hydrogen diffusion.Besides,AB_(4)-type alloy shows long lifespan whose capacity retention rates are 89.2%at the 100;cycle and 82.8%at the 200;cycle,respectively.AB_(4)-type alloy delivers 1.53 wt.%hydrogen storage capacity at room temperature and exhibits higher plateau pressure than Pr_(5)Co_(19)-type alloy.The work provides novel AB_(4)-type alloy with preferable electrochemical performance as negative electrode material to inspire the development of nickel metal hydride batteries.展开更多
With the increased use of renewable energy sources,the need to store large amounts of energy will become increasingly important in the near future.A cost efficient possibility is to use the reaction of recycled Mg was...With the increased use of renewable energy sources,the need to store large amounts of energy will become increasingly important in the near future.A cost efficient possibility is to use the reaction of recycled Mg waste with hydrogen as thermo-chemical energy storage.Owing to the high reaction enthalpy,the moderate pressure and appropriate temperature conditions,the broad abundance and the recyclability,the Mg/Al alloy is perfectly suitable for this purpose.As further development of a previous work,in which the performance of recycled Mg/Al waste was presented,a kinetic model for hydro-and dehydrogenation is derived in this study.Temperature and pressure dependencies are determined,as well as the rate limiting step of the reaction.First experiments are carried out in an autoclave with a scaled-up powder mass,which is also used to validate the model by simulating the geometry with the scaled-up experiments at different conditions.展开更多
The simulation of hydrogen purification in a mixture gas of hydrogen/carbon dioxide (H2/CO2) by metal hydride system was reported.The lumped parameter model was developed and validated.The validated model was implemen...The simulation of hydrogen purification in a mixture gas of hydrogen/carbon dioxide (H2/CO2) by metal hydride system was reported.The lumped parameter model was developed and validated.The validated model was implemented on the software Matlab/Simulink to simulate the present investigation.The simulation results demonstrate that the purification efficiency depends on the external pressure and the venting time.An increase in the external pressure and enough venting time makes it possible to effectively remove the impurities from the tank during the venting process and allows to desorb pure hydrogen.The impurities are partially removed from the tank for low external pressure and venting time during the venting process and the desorbed hydrogen is contaminated.Other parameters such as the overall heat transfer coefficient,solid material mass,supply pressure,and the ambient temperature influence the purification system in terms of the hydrogen recovery rate.An increase in the overall heat transfer coefficient,solid material mass,and supply pressure improves the hydrogen recovery rate while a decrease in the ambient temperature enhances the recovery rate.展开更多
Over the last decade’s magnesium and magnesium based compounds have been intensively investigated as potential hydrogen storage as well as thermal energy storage materials due to their abundance and availability as w...Over the last decade’s magnesium and magnesium based compounds have been intensively investigated as potential hydrogen storage as well as thermal energy storage materials due to their abundance and availability as well as their extraordinary high gravimetric and volumetric storage densities.This review work provides a broad overview of the most appealing systems and of their hydrogenation/dehydrogenation properties.Special emphasis is placed on reviewing the efforts made by the scientific community in improving the material’s thermodynamic and kinetic properties while maintaining a high hydrogen storage capacity.展开更多
High hydrogen absorption and desorption rates are two significant index parameters for the applications of hydrogen storage tanks.The analysis of the hydrogen absorption and desorption behavior using the isothermal ki...High hydrogen absorption and desorption rates are two significant index parameters for the applications of hydrogen storage tanks.The analysis of the hydrogen absorption and desorption behavior using the isothermal kinetic models is an efficient way to investigate the kinetic mechanism.Multitudinous kinetic models have been developed to describe the kinetic process.However,these kinetic models were de-duced based on some assumptions and only appropriate for specific kinetic measurement methods and rate-controlling steps(RCSs),which sometimes lead to confusion during application.The kinetic analysis procedures using these kinetic models,as well as the key kinetic parameters,are unclear for many researchers who are unfamiliar with this field.These problems will prevent the kinetic models and their analysis methods from revealing the kinetic mechanism of hydrogen storage alloys.Thus,this review mainly focuses on the summarization of kinetic models based on different kinetic measurement methods and RCSs for the chemisorption,surface penetration,diffusion of hydrogen,nucleation and growth,and chemical reaction processes.The analysis procedures of kinetic experimental data are expounded,as well as the effects of temperature,hydrogen pressure,and particle radius.The applications of the kinetic models for different hydrogen storage alloys are also introduced.展开更多
Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and transportation.Compared to nano powders which require handling and processing under hydrogen o...Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and transportation.Compared to nano powders which require handling and processing under hydrogen or an inert gas atmosphere,bulk Mg-based alloys are safer and are more oxidation re-sistant.Conventional methods and existing infrastructures can be used to process and handle these ma-terials.However,bulk Mg alloys have smaller specific surface areas,resulting in slower hydrogen sorp-tion kinetics,higher equilibrium temperatures,and enthalpies of hydride formation.This work reviews the effects of the additions of a list of alloying elements and the use of innovative processing meth-ods,e.g.,rapid solidification and severe plastic deformation processes,to overcome these drawbacks.The challenges,advantages,and weaknesses of each method and future perspectives for the development of Mg-based hydrogen storage materials are discussed.展开更多
Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hy...Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hydrogen(H~-) show promises for Nfixation and hydrogenation to ammonia. Herein, we report that rare earth metal hydrides such as lanthanum hydride can also fix Neither by heating to 200 °C or ball milling under ambient Npressure and temperature. The Nfixation by lanthanum hydride may proceed via an intermediate lanthanum hydride-nitride(La-H-N) structure to form the final lanthanum nitride product. The hydride ion functions as an electron donor, which provides electrons for Nactivation possibly mediated by the lanthanum atoms. It is observed that N–H bond is not formed during the Nfixation process, which is distinctly different from the alkali or alkaline earth metal hydrides. The hydrolysis of La-H-N to ammonia is feasible using water as the hydrogen source. These results provide new insights into the nitrogen fixation by hydride materials and more efforts are needed for the development of rare earth metal-based catalysts and/or nitrogen carriers for ammonia synthesis processes.展开更多
Metal hydride(MH)systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones.Recently,the possibility of using passive heating/co...Metal hydride(MH)systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones.Recently,the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling fluid.Natural convection of air may be used to passively remove/add heat as required for proper operation of a MH reactor.Under these conditions,the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of hydrogen.Since operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet,a tubular MH reactor based on this principle is examined in this paper.Two-thirds of the internal volume ofø25.4×1 mm tube is occupied by a composition of LaNi5 and aluminium foam(one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2).Annular fins are used to increase heat transfer to air.Detailed and simplified mathematical models of the systems of this class are proposed and validated.It is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining characteristics.Charging from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30℃ takes 15 min.A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30-300 W fuel cells.展开更多
An advanced ANSYS FLUENT-based model was developed for hydrogen recovery from a multi-tubular fixed-bed metal hydride(MH)reactor of large-scale design.The model was firstly validated by comparing its results to specif...An advanced ANSYS FLUENT-based model was developed for hydrogen recovery from a multi-tubular fixed-bed metal hydride(MH)reactor of large-scale design.The model was firstly validated by comparing its results to specific experimental data.Mass and heat transfer processes inside the fixed bed were investigated for various pressures and thermochemical characteristics of the MH(thermal conductivity,porosity and reaction parameters).The findings were reported as average,local and spatial changes in the metal’s bed temperature and hydrogen content.During the initial stage of the endothermic desorption(t<100 s),the bed temperature dropped dramat-ically in all cases.During this time,there was a massive emission of hydrogen.The bed temperature was then raised due to the reactor’s external convective heating,while the hydrogen release continued until the MH was completely dehydrided.The dehydrogenation rate of the MH was enhanced when the discharge pressure was raised.Furthermore,some other characteristics of the MH,i.e.,porosity,thermal conductivity,desorption rate constant and activation energy,significantly impacted the resulting mass and heat fluxes inside the bed material.展开更多
We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of ...We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds.Both 1 and 2 react with HBpin by adding the B-H bond across the Ni-X bond (X=O or N),giving rise to the 18-electron Ni(II)-H active species,[H1(Bpin)]and[H_(2)(Bpin)].Subtle tuning of the Ni-X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R_(2)PC_(6)H_(4)X).Unlike[H_(2)(Bpin)],the activation of HBpin in[H1(Bpin)]is reversible,which enables the Ni-O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes,and as well as ketones and imines.展开更多
Nickel metal hydride(Ni-MH) rechargeable batteries hold an important position in the new-energy vehicle market owing to their key technology advantages. Their negative electrode materials—hydrogen storage alloys(HSAs...Nickel metal hydride(Ni-MH) rechargeable batteries hold an important position in the new-energy vehicle market owing to their key technology advantages. Their negative electrode materials—hydrogen storage alloys(HSAs) are always on the spotlight and are the key to compete with the burgeoning Li-ion batteries. Here, for the first time we report a series of biphase supperlattice HSAs with a(La,Mg)_(2)Ni_7 matrix phase and a novel(La,Mg)_(7)Ni_(23) secondary phase. The biphase alloys show discharge capacities of402–413 m Ahg^(-1) compared with 376–397 mAhg^(-1) of the other multi-or single-phase alloys. These values are among the highest for superlattice HSAs. In addition, the alloy with 15.4 wt.%(La,Mg)_(7)Ni_(23) phase exhibits good high rate dischargeability due to the proper compromise between the amount of crystal boundaries and equilibrium plateau voltage. The cycling stability of the biphase alloys is lower than that of the single-phase alloy but is till higher than the multiphase alloy. The novel superlattice biphase alloys with superior overall electrochemical properties are expected to inspire further design and development of HSAs as advanced electrode materials for power batteries.展开更多
Composite LaNi5+x wt.% Ti0.10Zr0.16V0.34Cr0.10Ni0.30 (x=0, 1, 5, 10) alloys were prepared by two-step re-melting. X-ray diffractometer (XRD), scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS),...Composite LaNi5+x wt.% Ti0.10Zr0.16V0.34Cr0.10Ni0.30 (x=0, 1, 5, 10) alloys were prepared by two-step re-melting. X-ray diffractometer (XRD), scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), inductively coupled plasma (ICP) and electrochemical impedance spectroscopy (EIS) analyses showed that the matrix phase of LaNi5 alloy with CaCu5 structure remained unchanged after additive alloy was added, the amount of the second phase increased with increasing x. The synergetic effect within constituent alloys appeared during the composite process. The electrochemical characteristics of the composite alloy electrodes were greatly improved, and the optimum composition was x=5, at which the low temperature dischargeability at 233 K was 87.37 %, and the maximum discharge capacity and the high rate dischargeability at discharge current density of 1800 mA/g were 326.1 mAh/g and 71.98 % at 303 K, respectively. The HRD was controlled by both the charge-transfer reaction of hydrogen on the electrode/electrolyte interface and hydrogen diffusion coefficient in the bulk of the alloys at discharge current density of 1800 mA/g.展开更多
The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations.As a basic step fo...The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations.As a basic step for examinations,the site preference of each alloying element in the stoichiometric and nonstoichiometric B2TiFe compounds was clarified considering possible antisite defects.Based on the revealed site preference,the effect of various possible ternary elements on the hydrogen storage was examined by focusing on the formation enthalpies of TiFeH and TiFeH_(2) hydrides,which were closely related to the change in the location of plateaus in the pressure-composition-temperature curve.Several physical properties such as the volume expansion due to hydride formation were also examined to provide additional criteria for selecting optimum alloying conditions in future alloying design processes.Candidate alloying elements that maximize the grain boundary embrittlement due to the solute segregation were proposed for the enhanced initial activation of TiFe-based hydrogen storage alloys.展开更多
基金the National Natural Science Foundation of China(Grant Nos.21902158,21773230,91945302)the National Key R&D Program of China(No.2021YFA1502803)LiaoNing Revitalization Talents Program(XLYC1807207),DICP I202104.
文摘Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.
基金the National Natural Science Foundation of China(No.50776094)the National High Technology Research and Development Program(863)of China(No.2006AA05Z135)
文摘Known as one of the most promising application of metal hydride(MH),the MH compressor can afford hydrogen with high pressure and high purity.Two AB5 type multi-component hydrogen storage alloys and vanadium are studied for the purpose of high pressure compression.A compact compression system has been built.Each designed small-size reactor contains seven special stainless-steel pipes.The single stage compressor can improve the hydrogen pressure from 2 up to 35 MPa with the hydrogen desorbed per unit mass of 207.8 mL/g.The two-stage compression can output hydrogen with pressure of 38 MPa steadily in whole 5.7 mol hydrogen output flow.However,its hydrogen desorbed per unit mass was only computed to 106.9 mL/g as a result of two reactors used in the cycle and the output mass of hydrogen increased less.
基金financially supported by the Natural Science Foundation of Hebei Province(Nos.E2019203414,E2020203081 and E2019203161)the National Natural Science Foundation of China(Nos.51701175 and 51971197)+1 种基金the Innovation Fund for the Graduate Students of Hebei Province(No.CXZZBS2020062)the Doctoral Fund of Yanshan University(No.BL19031)
文摘Rare earth-Mg-Ni-based alloys with superlattice structures are new generation negative electrode materials for the nickel metal hydride batteries.Among them,the novel AB_(4)-type superlattice structure alloy is supposed to have superior cycling stability and rate capability.Yet its preparation is hindered by the crucial requirement of temperature and the special composition which is close to the other superlattice structure.Here,we prepare rare earth-Mg-Ni-based alloy and study the phase transformation of alloys to make clear the formation of AB_(4)-type phase.It is found Pr_(5)Co_(19)-type phase is converted from Ce_(5)Co_(19)-type phase and shows good stability at higher temperature compared to the Ce_(5)Co_(19)-type phase in the range of 930-970℃.Afterwards,with further 5℃increasing,AB_(4)-type superlattice structure forms at a temperature of 975℃by consuming Pr_(5)Co_(19)-type phase.In contrast with A_(5)B_(19)-type alloy,AB_(4)-type alloy has superior rate capability owing to the dominant advantages of charge transfer and hydrogen diffusion.Besides,AB_(4)-type alloy shows long lifespan whose capacity retention rates are 89.2%at the 100;cycle and 82.8%at the 200;cycle,respectively.AB_(4)-type alloy delivers 1.53 wt.%hydrogen storage capacity at room temperature and exhibits higher plateau pressure than Pr_(5)Co_(19)-type alloy.The work provides novel AB_(4)-type alloy with preferable electrochemical performance as negative electrode material to inspire the development of nickel metal hydride batteries.
文摘With the increased use of renewable energy sources,the need to store large amounts of energy will become increasingly important in the near future.A cost efficient possibility is to use the reaction of recycled Mg waste with hydrogen as thermo-chemical energy storage.Owing to the high reaction enthalpy,the moderate pressure and appropriate temperature conditions,the broad abundance and the recyclability,the Mg/Al alloy is perfectly suitable for this purpose.As further development of a previous work,in which the performance of recycled Mg/Al waste was presented,a kinetic model for hydro-and dehydrogenation is derived in this study.Temperature and pressure dependencies are determined,as well as the rate limiting step of the reaction.First experiments are carried out in an autoclave with a scaled-up powder mass,which is also used to validate the model by simulating the geometry with the scaled-up experiments at different conditions.
基金Funded by National Natural Science Foundation of China(No.51476120)111 Project(No.B17034)the Innovative Research Team Development Program of Ministry of Education of China(No.IRT17R83)。
文摘The simulation of hydrogen purification in a mixture gas of hydrogen/carbon dioxide (H2/CO2) by metal hydride system was reported.The lumped parameter model was developed and validated.The validated model was implemented on the software Matlab/Simulink to simulate the present investigation.The simulation results demonstrate that the purification efficiency depends on the external pressure and the venting time.An increase in the external pressure and enough venting time makes it possible to effectively remove the impurities from the tank during the venting process and allows to desorb pure hydrogen.The impurities are partially removed from the tank for low external pressure and venting time during the venting process and the desorbed hydrogen is contaminated.Other parameters such as the overall heat transfer coefficient,solid material mass,supply pressure,and the ambient temperature influence the purification system in terms of the hydrogen recovery rate.An increase in the overall heat transfer coefficient,solid material mass,and supply pressure improves the hydrogen recovery rate while a decrease in the ambient temperature enhances the recovery rate.
文摘Over the last decade’s magnesium and magnesium based compounds have been intensively investigated as potential hydrogen storage as well as thermal energy storage materials due to their abundance and availability as well as their extraordinary high gravimetric and volumetric storage densities.This review work provides a broad overview of the most appealing systems and of their hydrogenation/dehydrogenation properties.Special emphasis is placed on reviewing the efforts made by the scientific community in improving the material’s thermodynamic and kinetic properties while maintaining a high hydrogen storage capacity.
基金This work was financially supported by the Chongqing Special Key Project of Technology Innovation and Applica-tion Development,China(No.cstc2019jscx-dxwtB0029)the National Natural Science Foundation of China(Nos.51871143 and U2102212)+1 种基金the Science and Technology Committee of Shanghai,China(No.19010500400)the Shanghai Rising-Star Program(No.21QA1403200).
文摘High hydrogen absorption and desorption rates are two significant index parameters for the applications of hydrogen storage tanks.The analysis of the hydrogen absorption and desorption behavior using the isothermal kinetic models is an efficient way to investigate the kinetic mechanism.Multitudinous kinetic models have been developed to describe the kinetic process.However,these kinetic models were de-duced based on some assumptions and only appropriate for specific kinetic measurement methods and rate-controlling steps(RCSs),which sometimes lead to confusion during application.The kinetic analysis procedures using these kinetic models,as well as the key kinetic parameters,are unclear for many researchers who are unfamiliar with this field.These problems will prevent the kinetic models and their analysis methods from revealing the kinetic mechanism of hydrogen storage alloys.Thus,this review mainly focuses on the summarization of kinetic models based on different kinetic measurement methods and RCSs for the chemisorption,surface penetration,diffusion of hydrogen,nucleation and growth,and chemical reaction processes.The analysis procedures of kinetic experimental data are expounded,as well as the effects of temperature,hydrogen pressure,and particle radius.The applications of the kinetic models for different hydrogen storage alloys are also introduced.
基金supported by the Australian Research Council (No.LP160100690)a Japan Society for the Promotion of Science (JSPS)Postdoctoral Fellowship for Research in Japan (Standard) (No.P22739)supported by an Aus-tralian Government Research Training Program (RTP)Scholarship.
文摘Bulk Mg-based hydrogen storage materials have the potential to provide a low-cost solution to diversify energy storage and transportation.Compared to nano powders which require handling and processing under hydrogen or an inert gas atmosphere,bulk Mg-based alloys are safer and are more oxidation re-sistant.Conventional methods and existing infrastructures can be used to process and handle these ma-terials.However,bulk Mg alloys have smaller specific surface areas,resulting in slower hydrogen sorp-tion kinetics,higher equilibrium temperatures,and enthalpies of hydride formation.This work reviews the effects of the additions of a list of alloying elements and the use of innovative processing meth-ods,e.g.,rapid solidification and severe plastic deformation processes,to overcome these drawbacks.The challenges,advantages,and weaknesses of each method and future perspectives for the development of Mg-based hydrogen storage materials are discussed.
基金the financial support from the National Key R&D Program of China(2021YFB4000401)the National Natural Science Foundation of China(Grant Nos.21922205,21872137,22109158,and 51801197)+2 种基金the Youth Innovation Promotion Association CAS(Grant Nos.2018213,2019189,2022180)the Liaoning Revitalization Talents Program(Grant Nos.XLYC2007173,XLYC2002076)the K.C.Wong Education Foundation(Grant No.GJTD-2018-06)。
文摘Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hydrogen(H~-) show promises for Nfixation and hydrogenation to ammonia. Herein, we report that rare earth metal hydrides such as lanthanum hydride can also fix Neither by heating to 200 °C or ball milling under ambient Npressure and temperature. The Nfixation by lanthanum hydride may proceed via an intermediate lanthanum hydride-nitride(La-H-N) structure to form the final lanthanum nitride product. The hydride ion functions as an electron donor, which provides electrons for Nactivation possibly mediated by the lanthanum atoms. It is observed that N–H bond is not formed during the Nfixation process, which is distinctly different from the alkali or alkaline earth metal hydrides. The hydrolysis of La-H-N to ammonia is feasible using water as the hydrogen source. These results provide new insights into the nitrogen fixation by hydride materials and more efforts are needed for the development of rare earth metal-based catalysts and/or nitrogen carriers for ammonia synthesis processes.
文摘Metal hydride(MH)systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones.Recently,the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling fluid.Natural convection of air may be used to passively remove/add heat as required for proper operation of a MH reactor.Under these conditions,the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of hydrogen.Since operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet,a tubular MH reactor based on this principle is examined in this paper.Two-thirds of the internal volume ofø25.4×1 mm tube is occupied by a composition of LaNi5 and aluminium foam(one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2).Annular fins are used to increase heat transfer to air.Detailed and simplified mathematical models of the systems of this class are proposed and validated.It is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining characteristics.Charging from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30℃ takes 15 min.A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30-300 W fuel cells.
基金supported by The Ministry of Higher Education and Scientific Research of Algeria(Project No.:A16N01UN250320220002)the General Directorate of Scientific Research and Technological Development(GD-SRTD)of Algeria.
文摘An advanced ANSYS FLUENT-based model was developed for hydrogen recovery from a multi-tubular fixed-bed metal hydride(MH)reactor of large-scale design.The model was firstly validated by comparing its results to specific experimental data.Mass and heat transfer processes inside the fixed bed were investigated for various pressures and thermochemical characteristics of the MH(thermal conductivity,porosity and reaction parameters).The findings were reported as average,local and spatial changes in the metal’s bed temperature and hydrogen content.During the initial stage of the endothermic desorption(t<100 s),the bed temperature dropped dramat-ically in all cases.During this time,there was a massive emission of hydrogen.The bed temperature was then raised due to the reactor’s external convective heating,while the hydrogen release continued until the MH was completely dehydrided.The dehydrogenation rate of the MH was enhanced when the discharge pressure was raised.Furthermore,some other characteristics of the MH,i.e.,porosity,thermal conductivity,desorption rate constant and activation energy,significantly impacted the resulting mass and heat fluxes inside the bed material.
基金the financial support from the National Natural Science Foundation of China (Nos. 22022102 and 22071010)the financial support from China Postdoctoral Science Foundation (No. 2021M700462)。
文摘We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds.Both 1 and 2 react with HBpin by adding the B-H bond across the Ni-X bond (X=O or N),giving rise to the 18-electron Ni(II)-H active species,[H1(Bpin)]and[H_(2)(Bpin)].Subtle tuning of the Ni-X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R_(2)PC_(6)H_(4)X).Unlike[H_(2)(Bpin)],the activation of HBpin in[H1(Bpin)]is reversible,which enables the Ni-O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes,and as well as ketones and imines.
基金financially supported by the National Natural Science Foundation of China(Nos.51801176 and 51701226)the Natural Science Foundation of Hebei Province(Nos.E2019203414 and E2020203081)the High-end Talent Support Program of Yangzhou University and the Qinglan Engineering Project of Yangzhou University。
文摘Nickel metal hydride(Ni-MH) rechargeable batteries hold an important position in the new-energy vehicle market owing to their key technology advantages. Their negative electrode materials—hydrogen storage alloys(HSAs) are always on the spotlight and are the key to compete with the burgeoning Li-ion batteries. Here, for the first time we report a series of biphase supperlattice HSAs with a(La,Mg)_(2)Ni_7 matrix phase and a novel(La,Mg)_(7)Ni_(23) secondary phase. The biphase alloys show discharge capacities of402–413 m Ahg^(-1) compared with 376–397 mAhg^(-1) of the other multi-or single-phase alloys. These values are among the highest for superlattice HSAs. In addition, the alloy with 15.4 wt.%(La,Mg)_(7)Ni_(23) phase exhibits good high rate dischargeability due to the proper compromise between the amount of crystal boundaries and equilibrium plateau voltage. The cycling stability of the biphase alloys is lower than that of the single-phase alloy but is till higher than the multiphase alloy. The novel superlattice biphase alloys with superior overall electrochemical properties are expected to inspire further design and development of HSAs as advanced electrode materials for power batteries.
基金Project supported by Foundation of State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CAS)
文摘Composite LaNi5+x wt.% Ti0.10Zr0.16V0.34Cr0.10Ni0.30 (x=0, 1, 5, 10) alloys were prepared by two-step re-melting. X-ray diffractometer (XRD), scanning electron microscopy (FESEM), energy dispersive spectrometry (EDS), inductively coupled plasma (ICP) and electrochemical impedance spectroscopy (EIS) analyses showed that the matrix phase of LaNi5 alloy with CaCu5 structure remained unchanged after additive alloy was added, the amount of the second phase increased with increasing x. The synergetic effect within constituent alloys appeared during the composite process. The electrochemical characteristics of the composite alloy electrodes were greatly improved, and the optimum composition was x=5, at which the low temperature dischargeability at 233 K was 87.37 %, and the maximum discharge capacity and the high rate dischargeability at discharge current density of 1800 mA/g were 326.1 mAh/g and 71.98 % at 303 K, respectively. The HRD was controlled by both the charge-transfer reaction of hydrogen on the electrode/electrolyte interface and hydrogen diffusion coefficient in the bulk of the alloys at discharge current density of 1800 mA/g.
基金supported by the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(Nos.NRF-2019M3E6A1103984 and NRF-2019M3D1A1079214)。
文摘The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations.As a basic step for examinations,the site preference of each alloying element in the stoichiometric and nonstoichiometric B2TiFe compounds was clarified considering possible antisite defects.Based on the revealed site preference,the effect of various possible ternary elements on the hydrogen storage was examined by focusing on the formation enthalpies of TiFeH and TiFeH_(2) hydrides,which were closely related to the change in the location of plateaus in the pressure-composition-temperature curve.Several physical properties such as the volume expansion due to hydride formation were also examined to provide additional criteria for selecting optimum alloying conditions in future alloying design processes.Candidate alloying elements that maximize the grain boundary embrittlement due to the solute segregation were proposed for the enhanced initial activation of TiFe-based hydrogen storage alloys.
