Hydrogen energy has been recognized as“Ultimate Power Source”in the 21st century.It is a boon in these days of energy crunches and concerns about climate change because of the characterized advantages,such as high e...Hydrogen energy has been recognized as“Ultimate Power Source”in the 21st century.It is a boon in these days of energy crunches and concerns about climate change because of the characterized advantages,such as high energy density,large calorific value,abundant resource,zero pollution,zero carbon emission,storable and renewable.State-of-the-art perspectives on tuning the stable thermodynamics and sluggish kinetics of dehydrogenation and re-hydrogenation of LiBH4,which has been regarded as a promising hydrogen storage alternative for onboard energy carrier applications have been discussed.Five major technological approaches are involved,including nanoengineering,catalyst modification,ions substitution,reactant destabilization and a novel process termed as high-energy ball milling with in-situ aerosol spraying(BMAS).It is worth noting that BMAS has the potential to help overcome the kinetic barriers for thermodynamically favorable systems like LiBH4 t MgH2 mixture and provide thermodynamic driving force to enhance hydrogen release at a lower temperature.展开更多
The formation conditions of MgB2 in 2LiBH4 ＋ MgH2 system during dehydrogenation were investigated and its mechanism was discussed. The results show that direct decomposition of LiBH4 is suppressed under relative high...The formation conditions of MgB2 in 2LiBH4 ＋ MgH2 system during dehydrogenation were investigated and its mechanism was discussed. The results show that direct decomposition of LiBH4 is suppressed under relative higher initial dehydrogenation pressure of 4.0×10^5 Pa, wherein LiBH4 reacts with Mg to yield MgB2, and 9.16% （mass fraction） hydrogen is released within 9.6 h at 450 ℃. However, under relatively lower initial dehydrogenation pressure of 1.0×10^2 Pa, LiBH4 decomposes independently instead of reacting with Mg, resulting in no formation of MgB2, and 7.91% hydrogen is desorbed within 5.2 h at 450 ℃. It is found that the dehydrogenation of 2LiBH4 ＋ MgH2 system proceeds more completely and more hydrogen desorption amount can be obtained within a definite time by forming MgB2. Furthermore, it is proposed that the formation process of MgB2 includes incubation period and nucleus growth process. Experimental results show that the formation process of MgB2, especially the incubation period, is promoted by increasing initial dehydrogenation pressure at constant temperature, and the incubation period is also influenced greatly by dehydrogenation temperature.展开更多
A first-principles study was reported based on density functional theory of hydrogen vacancy,metal dopants,metal dopant-vacancy complex in LiBH4,a promising material for hydrogen storage.The formation of H vacancy and...A first-principles study was reported based on density functional theory of hydrogen vacancy,metal dopants,metal dopant-vacancy complex in LiBH4,a promising material for hydrogen storage.The formation of H vacancy and metal doping in LiBH4 is difficult,and their concentrations are low.The presence of one kind of defect is helpful to the formation of other kind of defect.Based on the analysis of electronic structure,the improvement of the dehydrogenating kinetics of LiBH4 by metal catalysts is due to the weaker bonding of B—H and the new metal-like system,which makes H atom diffuse easily;H vacancy accounts for a trace amount of BH3 release during the decomposing process of LiBH4;metal dopant weakens the strength of B—H bonds,which reduces the dehydriding temperature of LiBH4.The roles of metal and vacancy in the metal dopant-vacancy complex can be added in LiBH4 system.展开更多
基金the U.S.National Science Foundation(NSF)with the Award No.CMMI-1261782.
文摘Hydrogen energy has been recognized as“Ultimate Power Source”in the 21st century.It is a boon in these days of energy crunches and concerns about climate change because of the characterized advantages,such as high energy density,large calorific value,abundant resource,zero pollution,zero carbon emission,storable and renewable.State-of-the-art perspectives on tuning the stable thermodynamics and sluggish kinetics of dehydrogenation and re-hydrogenation of LiBH4,which has been regarded as a promising hydrogen storage alternative for onboard energy carrier applications have been discussed.Five major technological approaches are involved,including nanoengineering,catalyst modification,ions substitution,reactant destabilization and a novel process termed as high-energy ball milling with in-situ aerosol spraying(BMAS).It is worth noting that BMAS has the potential to help overcome the kinetic barriers for thermodynamically favorable systems like LiBH4 t MgH2 mixture and provide thermodynamic driving force to enhance hydrogen release at a lower temperature.
基金Project (2010CB631300) supported by the National Basic Research Program of China Project (50631020) supported by the National Natural Science Foundation of China+1 种基金 Project (NCET-07-0741) supported by the Program for New Century Excellent Talents in Universities, ChinaProject (20090101110050) supported by the University Doctoral Foundation of the Ministry of Education, China
文摘The formation conditions of MgB2 in 2LiBH4 ＋ MgH2 system during dehydrogenation were investigated and its mechanism was discussed. The results show that direct decomposition of LiBH4 is suppressed under relative higher initial dehydrogenation pressure of 4.0×10^5 Pa, wherein LiBH4 reacts with Mg to yield MgB2, and 9.16% （mass fraction） hydrogen is released within 9.6 h at 450 ℃. However, under relatively lower initial dehydrogenation pressure of 1.0×10^2 Pa, LiBH4 decomposes independently instead of reacting with Mg, resulting in no formation of MgB2, and 7.91% hydrogen is desorbed within 5.2 h at 450 ℃. It is found that the dehydrogenation of 2LiBH4 ＋ MgH2 system proceeds more completely and more hydrogen desorption amount can be obtained within a definite time by forming MgB2. Furthermore, it is proposed that the formation process of MgB2 includes incubation period and nucleus growth process. Experimental results show that the formation process of MgB2, especially the incubation period, is promoted by increasing initial dehydrogenation pressure at constant temperature, and the incubation period is also influenced greatly by dehydrogenation temperature.
基金Project (2009AA05Z105) supported by the High-tech Research and Development Program of ChinaProject (20102173) supported by the Natural Science Foundation of Liaoning Province,China
文摘A first-principles study was reported based on density functional theory of hydrogen vacancy,metal dopants,metal dopant-vacancy complex in LiBH4,a promising material for hydrogen storage.The formation of H vacancy and metal doping in LiBH4 is difficult,and their concentrations are low.The presence of one kind of defect is helpful to the formation of other kind of defect.Based on the analysis of electronic structure,the improvement of the dehydrogenating kinetics of LiBH4 by metal catalysts is due to the weaker bonding of B—H and the new metal-like system,which makes H atom diffuse easily;H vacancy accounts for a trace amount of BH3 release during the decomposing process of LiBH4;metal dopant weakens the strength of B—H bonds,which reduces the dehydriding temperature of LiBH4.The roles of metal and vacancy in the metal dopant-vacancy complex can be added in LiBH4 system.
