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
Contrary to the popular opinion, it has been found that metallic Ti powder can be directly utilized as dopant precursor to prepare catalytically enhanced NaAlH4 through mechanical milling. As a novel method for prepar...Contrary to the popular opinion, it has been found that metallic Ti powder can be directly utilized as dopant precursor to prepare catalytically enhanced NaAlH4 through mechanical milling. As a novel method for preparation of catalytically enhanced NaAlH4, direct metallic Ti-doping possesses practical advantage over the state-of-the-art doping technology: elimination of the inactive by-products and the gas impurities that are highly detrimental to fuel cell operation. A systematic investigation along this new approach was performed under various preparation conditions, including different starting materials, milling atmosphere and milling time. The materials thus prepared under different conditions were found to share some common features, while at the meantime, differ significantly from each other on hydrogen storage performance. A comprehensive understanding of these results provides valuable insight into a series of fundamental questions in catalytically enhanced Ti-NaAlH4 system.展开更多
A new type of AB_5-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composite hydrogen storage alloys were prepared by sintering the powder mixtures of a commercial AB_5 alloy and LaMg_3 alloy. The phase structure and electrochemical c...A new type of AB_5-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composite hydrogen storage alloys were prepared by sintering the powder mixtures of a commercial AB_5 alloy and LaMg_3 alloy. The phase structure and electrochemical characteristics of the composite hydrogen storage alloys were also studied. It is shown that AB_(5)-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composites have mult; phase structure. The matrix phase has CaCu_5 structure, the second phase is LaNi_3 phase. The maximum discharge capacity, discharge capacity at low temperature and HRD of AB_5 alloy electrodes are greatly improved after the composite. The maximum discharge capacity of the composite electrodes increases from 325 mAh·g^(-1) for x=0 to 358 mAh·g^(-1) for x=5, and the HRD of the composites for x=5 at the current density of 1200 mA·g^(-1)30% of that of the alloy at 60 mA·g^(-1). The discharge capacity of AB_5-x%LaMg_3 composite alloy electrode at 233 K is up to 174 mAh·g^(-1). The improvement of the electrochemical characteristics of the composite electrodes seems to be related with formation of the LaNi_3 second phase.展开更多
Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels. One of the key challenges to commercialize hydrogen energy is to develop ap...Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels. One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems, capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements. Metal organic framework （MOF） is a new type of inorganic and organic hybrid nanoporous particulate materials. Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs. The MOF materials so far developed adsorb hydrogen through weak dispersion interactions, which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics. Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions. This review surveys the development of such candidate materials, their performance and future research needs.展开更多
Hydrogen storage material has been much developed recently because of its potential for proton exchange membrane （PEM） fuel cell applications. A successful solid-state reversible storage material should meet the req...Hydrogen storage material has been much developed recently because of its potential for proton exchange membrane （PEM） fuel cell applications. A successful solid-state reversible storage material should meet the requirements of high storage capacity, suitable thermodynamic properties, and fast adsorption and desorption kinetics. Complex hydrides, including boron hydride and alanate, ammonia borane, metal organic frameworks （MOFs）, covalent organic frameworks （COFs） and zeolitic imidazolate frameworks （ZIFs）, are remarkable hydrogen storage materials because of their advantages of high energy density and safety. This feature article focuses mainly on the thermodynamics and kinetics of these hydrogen storage materials in the past few years.展开更多
The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg（BH4）2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. ...The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg（BH4）2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. It is found that the ambient pressure phases of meta-stable I41/amd and unstable P-3ml proposed recently are extra stable and cannot decompose under high pressure. Enthalpy calculation indicates that the ground state of F222 structure proposed by Zhou et al. [2009 Phys. Rev. B 79 212102] will transfer to I41/amd at 0.7 GPa, and then to a P-3ml structure at 6.3 GPa. The experimental P6122 structure （a-phase） transfers to I41/amd at 1.2 GPa. Furthermore, both I41/arnd and P-3ml can exist as high volumetric hydrogen density phases at low pressure. Their theoretical volumetric hydrogen densities reach 146.351 g H2/L and 134.028 g H2/L at ambient pressure, respectively. The calculated phonon dispersion curve shows that the I41/amd phase is dynamically stable in a pressure range from 0 to 4 CPa and the P-3ral phase is stable at pressures higher than 1 GPa. So the I41/arnd phase may be synthesized under high pressure and retained to ambient pressure. Energy band structures show that they are both always ionic crystalline and insulating with a band-gap of about 5 eV in this pressure range. In addition, they each have an anisotropic compressibility. The c axis of these structures is easy to compress. Especially, the c axis and volume of P-3ml phase are extraordinarily compressible, showing that compression along the e axis can increase the volumetric hydrogen content for both I41/amd and P-3ml structures.展开更多
Reactive mechanical alloying(RMA)was carried out in a planetary ball mill for the synthesis of ternary hydride Mg2FeH6 for hydrogen storage.The formation mechanism of Mg2FeH6 in RMA process and the sorption properties...Reactive mechanical alloying(RMA)was carried out in a planetary ball mill for the synthesis of ternary hydride Mg2FeH6 for hydrogen storage.The formation mechanism of Mg2FeH6 in RMA process and the sorption properties of the products were investigated.The results show that Mg2FeH6 has a yield ratio around 80%,and a grain size below 10 nm in the powder synthesized by milling 3Mg+Fe mixture for 150 h under the hydrogen pressure of 1 MPa.The synthesized powder possesses a high hydrogen capacity and good sorption kinetics,and absorbs 4.42%(mass fraction)of hydrogen within 200 s at 623 K under the hydrogen pressure of 4.0 MPa.In releasing hydrogen at 653 K under 0.1 MPa,it desorbs 4.43%(mass fraction)of hydrogen within 2 000 s.The addition of Ti increases the hydrogen desorption rate of the complex in the initial 120 s of the desorption process.展开更多
Modified iron oxide, a new material for hydrogen storage and supply to polymer electrolyte fuel cell （PEFC）, was prepared by impregnating Fe or Fe2O3 powder with an aqueous solution containing metal cation additives...Modified iron oxide, a new material for hydrogen storage and supply to polymer electrolyte fuel cell （PEFC）, was prepared by impregnating Fe or Fe2O3 powder with an aqueous solution containing metal cation additives （Al, Cr, Ni, Co, Zr and Mo）. Hydrogen storage properties of the samples were investigated. The results show that both Fe and Fe2O3 powder with additive Mo presented excellent catalytic activity and cyclic stability, and their hydrogen producing temperature could be surprisingly decreased. The temperature of forming hydrogen for the Fe2O3-Mo at the rate of 250 μmol·min^-1·Fe-g^-1 could be dramatically decreased from 527 ℃ before addition of Mo to 283 ℃ after addition of Mo in the fourth cycle. The cause for it was probably related to preventing the sinter of the sample particles. In addition, hydrogen storage capacity of the Fe2O3-Mo can reach w=4.5% （72 kg H2/m^3）, close to International Energy Agency （IEA） criterion. These show the value of practical application of the Fe2O3-Mo as the promising hydrogen storage material.展开更多
Hydrogen is recognized as a promising energy scours in the close future.Online hydrogen preparation from formic acid under mild reaction conditions causes extensive interests.Mo_(2)C and metal(Fe,Ni,Co,K)doped Mo_(2)C...Hydrogen is recognized as a promising energy scours in the close future.Online hydrogen preparation from formic acid under mild reaction conditions causes extensive interests.Mo_(2)C and metal(Fe,Ni,Co,K)doped Mo_(2)C on granular activated carbon(GAC)were prepared and used as heterogeneous catalysts for H2 generation from formic acid on a fixed bed reactor at 100–250°C.The formic acid conversions on doped Mo_(2)C-Me/GAC are clearly improved,especially at lower reaction temperatures.Co doping presents outstanding effect on H2 selectivity and conversion rate compared to Ni and Fe.A 56.3%formic acid conversion was reached on Mo_(2)C-Co/GAC at 100°C,which triples that on Mo_(2)C/GAC at the same temperature.At 150°C,a high formic acid conversion over 90%was reached on Mo_(2)C-Co/GAC.These long lifetime catalysts with no precious metal provide a low cost route to hydrogen production from formic acid.展开更多
The influence of elemental composition on the crystal structure, hydrogen storage and electrochemical properties for Mg-contain- ing alloys was investigated. As La/Mg ratio decreased, the slight change of Ni content w...The influence of elemental composition on the crystal structure, hydrogen storage and electrochemical properties for Mg-contain- ing alloys was investigated. As La/Mg ratio decreased, the slight change of Ni content was detected. XRD results indicated that these alloys were composed of LaNi5 and Mg-containing phases. The lattice parameters of Mg-containing phases decreased. Meanwhile, the mass fraction of Mg-containing phases varied with the change of La/Mg and Ni. The hydrogen storage capacity reached -1.6 wt.% for La/Mg ≥ 3：1 and de- creased to -0.71 wt.% for La/Mg=1. Two hydrogen absorption processes were observed because of the existence of the multiphases for La/Mg ≥ 3：1. With decreasing La/Mg ratio, the equilibrium pressure rose due to the shrinkage of the lattice parameter. Meanwhile, one hy- drogen absorption process was obviously present. The discharge capacity of these as-cast alloys was higher, but the cyclic stability was poor for La/Mg ≥ 3：1 due to the partial amorphisation. It was better for La/Mg≤2 although the discharge capacity was lower. The polarization re- sistance increased, contrarily the exchange current density decreased with decreasing Mg content.展开更多
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 financial by supported by Hundred Talents Project of Chinese Academy of Sciences and the National Natural Science Foundation of China (No.50571099).
文摘Contrary to the popular opinion, it has been found that metallic Ti powder can be directly utilized as dopant precursor to prepare catalytically enhanced NaAlH4 through mechanical milling. As a novel method for preparation of catalytically enhanced NaAlH4, direct metallic Ti-doping possesses practical advantage over the state-of-the-art doping technology: elimination of the inactive by-products and the gas impurities that are highly detrimental to fuel cell operation. A systematic investigation along this new approach was performed under various preparation conditions, including different starting materials, milling atmosphere and milling time. The materials thus prepared under different conditions were found to share some common features, while at the meantime, differ significantly from each other on hydrogen storage performance. A comprehensive understanding of these results provides valuable insight into a series of fundamental questions in catalytically enhanced Ti-NaAlH4 system.
文摘A new type of AB_5-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composite hydrogen storage alloys were prepared by sintering the powder mixtures of a commercial AB_5 alloy and LaMg_3 alloy. The phase structure and electrochemical characteristics of the composite hydrogen storage alloys were also studied. It is shown that AB_(5)-x%LaMg_3(x=2, 3, 4, 5, 6, 7, 8)composites have mult; phase structure. The matrix phase has CaCu_5 structure, the second phase is LaNi_3 phase. The maximum discharge capacity, discharge capacity at low temperature and HRD of AB_5 alloy electrodes are greatly improved after the composite. The maximum discharge capacity of the composite electrodes increases from 325 mAh·g^(-1) for x=0 to 358 mAh·g^(-1) for x=5, and the HRD of the composites for x=5 at the current density of 1200 mA·g^(-1)30% of that of the alloy at 60 mA·g^(-1). The discharge capacity of AB_5-x%LaMg_3 composite alloy electrode at 233 K is up to 174 mAh·g^(-1). The improvement of the electrochemical characteristics of the composite electrodes seems to be related with formation of the LaNi_3 second phase.
文摘Hydrogen is expected to play an important role in future transportation as a promising alternative clean energy source to carbon-based fuels. One of the key challenges to commercialize hydrogen energy is to develop appropriate onboard hydrogen storage systems, capable of charging and discharging large quantities of hydrogen with fast enough kinetics to meet commercial requirements. Metal organic framework （MOF） is a new type of inorganic and organic hybrid nanoporous particulate materials. Its diverse networks can enhance hydrogen storage through tuning the structure and property of MOFs. The MOF materials so far developed adsorb hydrogen through weak dispersion interactions, which allow significant quantity of hydrogen to be stored at cryogenic temperatures with fast kinetics. Novel MOFs are being developed to strengthen the interactions between hydrogen and MOFs in order to store hydrogen under ambient conditions. This review surveys the development of such candidate materials, their performance and future research needs.
基金Acknowledgements The authors gratefully acknowledged the financial support for this work from the National Basic Research Program of China （973 Program） （Grant No. 2010CB631303）, the National Natural Science Foundation of China （Grant Nos. 20833009, 20873148, 20903095, 50901070, 51071146, 51071081, and U0734005）, IUPAC （Project No. 2008-006-3-100）, Dalian Science and Technology Foundation （Grant No. 2009AllGX052）, Liaoning BaiQianWan Talents Program （Project No. 2010921050）, and the State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology （Grant No. KFJJ10-1Z）.
文摘Hydrogen storage material has been much developed recently because of its potential for proton exchange membrane （PEM） fuel cell applications. A successful solid-state reversible storage material should meet the requirements of high storage capacity, suitable thermodynamic properties, and fast adsorption and desorption kinetics. Complex hydrides, including boron hydride and alanate, ammonia borane, metal organic frameworks （MOFs）, covalent organic frameworks （COFs） and zeolitic imidazolate frameworks （ZIFs）, are remarkable hydrogen storage materials because of their advantages of high energy density and safety. This feature article focuses mainly on the thermodynamics and kinetics of these hydrogen storage materials in the past few years.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB808200)the National Natural Science Foundation of China (Grant Nos. 51032001,11074090,10979001,and 51025206)the Funds for Changjiang Scholar and Innovative Research Team in University (Grant No. IRT1132)
文摘The previously proposed theoretical and experimental structures, bond characterization, and compressibility of Mg（BH4）2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations. It is found that the ambient pressure phases of meta-stable I41/amd and unstable P-3ml proposed recently are extra stable and cannot decompose under high pressure. Enthalpy calculation indicates that the ground state of F222 structure proposed by Zhou et al. [2009 Phys. Rev. B 79 212102] will transfer to I41/amd at 0.7 GPa, and then to a P-3ml structure at 6.3 GPa. The experimental P6122 structure （a-phase） transfers to I41/amd at 1.2 GPa. Furthermore, both I41/arnd and P-3ml can exist as high volumetric hydrogen density phases at low pressure. Their theoretical volumetric hydrogen densities reach 146.351 g H2/L and 134.028 g H2/L at ambient pressure, respectively. The calculated phonon dispersion curve shows that the I41/amd phase is dynamically stable in a pressure range from 0 to 4 CPa and the P-3ral phase is stable at pressures higher than 1 GPa. So the I41/arnd phase may be synthesized under high pressure and retained to ambient pressure. Energy band structures show that they are both always ionic crystalline and insulating with a band-gap of about 5 eV in this pressure range. In addition, they each have an anisotropic compressibility. The c axis of these structures is easy to compress. Especially, the c axis and volume of P-3ml phase are extraordinarily compressible, showing that compression along the e axis can increase the volumetric hydrogen content for both I41/amd and P-3ml structures.
基金Project(50574105)supported by the National Natural Science Foundation of ChinaProject(10JJ2037)supported by Hunan Provincial Natural Science Foundation of ChinaProject(200902)supported by Innovation Foundation of State Key Laboratory for Powder Metallurgy,Central South University,China
文摘Reactive mechanical alloying(RMA)was carried out in a planetary ball mill for the synthesis of ternary hydride Mg2FeH6 for hydrogen storage.The formation mechanism of Mg2FeH6 in RMA process and the sorption properties of the products were investigated.The results show that Mg2FeH6 has a yield ratio around 80%,and a grain size below 10 nm in the powder synthesized by milling 3Mg+Fe mixture for 150 h under the hydrogen pressure of 1 MPa.The synthesized powder possesses a high hydrogen capacity and good sorption kinetics,and absorbs 4.42%(mass fraction)of hydrogen within 200 s at 623 K under the hydrogen pressure of 4.0 MPa.In releasing hydrogen at 653 K under 0.1 MPa,it desorbs 4.43%(mass fraction)of hydrogen within 2 000 s.The addition of Ti increases the hydrogen desorption rate of the complex in the initial 120 s of the desorption process.
基金Project supported by the National Natural Science Foundation of China （No. 20673082）, the Scientific Research Foundation for the Returned 0verseas Chinese Scholars, State Education Ministry （No. 2006331）, the Key Project of Science and Technology of Shaanxi Province （No. 2005k07-G2）, and the Natural Science Foundation of Shaanxi Education Committee （No. 06JK167）.
文摘Modified iron oxide, a new material for hydrogen storage and supply to polymer electrolyte fuel cell （PEFC）, was prepared by impregnating Fe or Fe2O3 powder with an aqueous solution containing metal cation additives （Al, Cr, Ni, Co, Zr and Mo）. Hydrogen storage properties of the samples were investigated. The results show that both Fe and Fe2O3 powder with additive Mo presented excellent catalytic activity and cyclic stability, and their hydrogen producing temperature could be surprisingly decreased. The temperature of forming hydrogen for the Fe2O3-Mo at the rate of 250 μmol·min^-1·Fe-g^-1 could be dramatically decreased from 527 ℃ before addition of Mo to 283 ℃ after addition of Mo in the fourth cycle. The cause for it was probably related to preventing the sinter of the sample particles. In addition, hydrogen storage capacity of the Fe2O3-Mo can reach w=4.5% （72 kg H2/m^3）, close to International Energy Agency （IEA） criterion. These show the value of practical application of the Fe2O3-Mo as the promising hydrogen storage material.
基金financial support of grant from the Natural Science Funds for Young Scholar of China(Grant No.21107049)the priority academic program development of Jiangsu Higher Education Institution(PAPD).
文摘Hydrogen is recognized as a promising energy scours in the close future.Online hydrogen preparation from formic acid under mild reaction conditions causes extensive interests.Mo_(2)C and metal(Fe,Ni,Co,K)doped Mo_(2)C on granular activated carbon(GAC)were prepared and used as heterogeneous catalysts for H2 generation from formic acid on a fixed bed reactor at 100–250°C.The formic acid conversions on doped Mo_(2)C-Me/GAC are clearly improved,especially at lower reaction temperatures.Co doping presents outstanding effect on H2 selectivity and conversion rate compared to Ni and Fe.A 56.3%formic acid conversion was reached on Mo_(2)C-Co/GAC at 100°C,which triples that on Mo_(2)C/GAC at the same temperature.At 150°C,a high formic acid conversion over 90%was reached on Mo_(2)C-Co/GAC.These long lifetime catalysts with no precious metal provide a low cost route to hydrogen production from formic acid.
基金Project supported by National Natural Science Foundation of China (50901030)Doctoral Science Foundation of Hebei Normal University (L2007B12)
文摘The influence of elemental composition on the crystal structure, hydrogen storage and electrochemical properties for Mg-contain- ing alloys was investigated. As La/Mg ratio decreased, the slight change of Ni content was detected. XRD results indicated that these alloys were composed of LaNi5 and Mg-containing phases. The lattice parameters of Mg-containing phases decreased. Meanwhile, the mass fraction of Mg-containing phases varied with the change of La/Mg and Ni. The hydrogen storage capacity reached -1.6 wt.% for La/Mg ≥ 3：1 and de- creased to -0.71 wt.% for La/Mg=1. Two hydrogen absorption processes were observed because of the existence of the multiphases for La/Mg ≥ 3：1. With decreasing La/Mg ratio, the equilibrium pressure rose due to the shrinkage of the lattice parameter. Meanwhile, one hy- drogen absorption process was obviously present. The discharge capacity of these as-cast alloys was higher, but the cyclic stability was poor for La/Mg ≥ 3：1 due to the partial amorphisation. It was better for La/Mg≤2 although the discharge capacity was lower. The polarization re- sistance increased, contrarily the exchange current density decreased with decreasing Mg content.
