LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversio...LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversion via anodic oxidation reaction of direct borohydride fuel cells(DBFCs).However,the realization of practical hydrogen applications heavily depends on the effective synthesis of high-purity LiBH_(4) and recycling of the spent fuels(LiBO_(2)·xH_(2)O).The present work demonstrates a convenient and high-efficiency solvent-free strategy for regenerating LiBH_(4) with a maximum yield close to 80%,by retrieving its by-products with MgH_(2) as a reducing agent under ambient conditions.Besides,the hydrogen released from the regeneration course can completely compensate the demand for consumed MgH_(2).The isotopic tracer method reveals that the hydrogen stored in LiBH_(4) comes from both MgH_(2) and coordinated water bound to LiBO_(2).Here,the expensive MgH_(2) can be substituted with the readily available and cost-effective MgH_(2)-Mg mixtures to simplify the regeneration route.Notably,LiBH_(4) catalyzed by CoCl_(2) can stably supply hydrogen to proton exchange membrane fuel cell(PEMFC),thus powering a portable prototype vehicle.By combining hydrogen storage,production and utilization in a closed cycle,this work offers new insights into deploying boron-based hydrides for energy applications.展开更多
The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))has a high capacity of 11.4 wt%as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a ...The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))has a high capacity of 11.4 wt%as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a layered Nb_(2)C MXene was first synthesized and then introduced to tailor the kinetics and cycling stability of the Li-Mg-B-H composite.The milled 2LiH+MgB_(2)composites were initially hydrogenated to obtain the 2LiBH_(4)+MgH_(2)composites.The 2LiBH_(4)+MgH_(2)+5wt%Nb_(2)C can release 9.0 wt%H_(2)in 30 min at 400℃,while it is only 2.7 wt%for the undoped 2LiBH_(4)+MgH_(2).The dehydrogenation activation energies of MgH_(2)and LiBH_(4)are 123 and 154 kJ·mol^(-1)respectively for the 5 wt%Nb_(2)C-doped composite,lower than the undoped composite(164 and 165 kJ·mol^(-1)).The 2LiBH_(4)+MgH_(2)+5 wt%Nb_(2)C possesses excellent cycling stability,with the reversible capacity only slightly reduced from 9.4 wt%for the 1st cycle to 9.3 wt%for the 20th cycle.Nb_(2)C keeps stable in the composite and acts as an efficient catalyst for the Li-Mg-B-H composite.It is believed that both the layered structure and the active Nb element contribu te to the enhanced hydrogen storage performances of the Li-Mg-B-H composite.This work confirms that the Nb_(2)C MXene with layered stru cture has a significant enhancing impact on the Li-Mg-B-H hydrogen storage materials,which is different from the bulk NbC.展开更多
MgH_(2),owing to a high theoretical capacity of 2038 mAh g^(−1),is regarded as a promising anode material for lithium-ion batteries(LIBs).However,the application of MgH_(2) is still far from satisfactory due to its po...MgH_(2),owing to a high theoretical capacity of 2038 mAh g^(−1),is regarded as a promising anode material for lithium-ion batteries(LIBs).However,the application of MgH_(2) is still far from satisfactory due to its poor cycling stability.Herein,nano-crystallization of MgH_(2) as an anode is applied for all-solid-state lithium-ion batteries(ASSLIBs)using LiBH4 as a solid-state electrolyte.The self-assembly designed MgH_(2) electrode on graphene could effectively alleviate the volume expansion,prevent the agglomeration of active substances,improve the electron transfer,and enhance the electrochemical performance of the anode material.As a result,a reversible capacity of 1214 mAh g^(−1) after 50 cycles is obtained.Significantly enhanced cycle life with a notable capacity of 597 mAh g^(−1) at a current density of 400 mA g^(−1) is delivered after 200 cycles.Further investigation on full cells also exhibits great application potential on ASSLIBs.展开更多
In order to improve the hydrogen storage properties of LiBH4-MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4-MgH2 composite by ball milling, and the effect of catalysts on ...In order to improve the hydrogen storage properties of LiBH4-MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4-MgH2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH4-MgH2 system was investigated. The experimental results show that LiBH4-MgH2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320℃, and there is a long period of incubation time(around 220 min) for the occurrence of the second decomposition step even at high temperature of 450℃. It needs more than 10 h to complete the decomposition process and release around 9 wt% H2. After addition of 5 mol% NbF5, the starting decomposition temperature for the first dehydrogenation step is around 150℃, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.展开更多
基金This work was financially supported by the National Natural Science Foundation of China Projects(Nos.51771075)the National Key R&D Program of China(No.2018YFB1502101)+2 种基金the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.NSFC51621001)by the Project Supported by Nat-ural Science Foundation of Guangdong Province of China(2016A030312011)Shao acknowledges support from Macao Science and Technology Development Fund(FDCT)(Project No.:0062/2018/A2 and 0019/2019/AGJ).
文摘LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversion via anodic oxidation reaction of direct borohydride fuel cells(DBFCs).However,the realization of practical hydrogen applications heavily depends on the effective synthesis of high-purity LiBH_(4) and recycling of the spent fuels(LiBO_(2)·xH_(2)O).The present work demonstrates a convenient and high-efficiency solvent-free strategy for regenerating LiBH_(4) with a maximum yield close to 80%,by retrieving its by-products with MgH_(2) as a reducing agent under ambient conditions.Besides,the hydrogen released from the regeneration course can completely compensate the demand for consumed MgH_(2).The isotopic tracer method reveals that the hydrogen stored in LiBH_(4) comes from both MgH_(2) and coordinated water bound to LiBO_(2).Here,the expensive MgH_(2) can be substituted with the readily available and cost-effective MgH_(2)-Mg mixtures to simplify the regeneration route.Notably,LiBH_(4) catalyzed by CoCl_(2) can stably supply hydrogen to proton exchange membrane fuel cell(PEMFC),thus powering a portable prototype vehicle.By combining hydrogen storage,production and utilization in a closed cycle,this work offers new insights into deploying boron-based hydrides for energy applications.
基金financially supported by the Science and Technology Department of Guangxi Zhuang Autonomous(No.GuiKeAD21238022)the National Natural Science Foundation of China(Nos.52001079,22379030 and 52261038)Quzhou Science and Technology Project(No.2022K103)。
文摘The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))has a high capacity of 11.4 wt%as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a layered Nb_(2)C MXene was first synthesized and then introduced to tailor the kinetics and cycling stability of the Li-Mg-B-H composite.The milled 2LiH+MgB_(2)composites were initially hydrogenated to obtain the 2LiBH_(4)+MgH_(2)composites.The 2LiBH_(4)+MgH_(2)+5wt%Nb_(2)C can release 9.0 wt%H_(2)in 30 min at 400℃,while it is only 2.7 wt%for the undoped 2LiBH_(4)+MgH_(2).The dehydrogenation activation energies of MgH_(2)and LiBH_(4)are 123 and 154 kJ·mol^(-1)respectively for the 5 wt%Nb_(2)C-doped composite,lower than the undoped composite(164 and 165 kJ·mol^(-1)).The 2LiBH_(4)+MgH_(2)+5 wt%Nb_(2)C possesses excellent cycling stability,with the reversible capacity only slightly reduced from 9.4 wt%for the 1st cycle to 9.3 wt%for the 20th cycle.Nb_(2)C keeps stable in the composite and acts as an efficient catalyst for the Li-Mg-B-H composite.It is believed that both the layered structure and the active Nb element contribu te to the enhanced hydrogen storage performances of the Li-Mg-B-H composite.This work confirms that the Nb_(2)C MXene with layered stru cture has a significant enhancing impact on the Li-Mg-B-H hydrogen storage materials,which is different from the bulk NbC.
基金financially supported by the National Natural Science Foundation of China(Nos.52171180,51802154,and 51971065)the National Science Fund for Distinguished Young Scholars(No.51625102)+3 种基金the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-07-E00028)the Fundamental Research Funds for the Central Universities(No.NG2022005)the Scientific and Technological Innovation Special Fund for Carbon Peak and Carbon Neutrality of Jiangsu Province(No.BK20220039)the Open Fund for Graduate Innovation Base in Nanjing University of Aeronautics and Astronautics(No.xcxjh20210612).
文摘MgH_(2),owing to a high theoretical capacity of 2038 mAh g^(−1),is regarded as a promising anode material for lithium-ion batteries(LIBs).However,the application of MgH_(2) is still far from satisfactory due to its poor cycling stability.Herein,nano-crystallization of MgH_(2) as an anode is applied for all-solid-state lithium-ion batteries(ASSLIBs)using LiBH4 as a solid-state electrolyte.The self-assembly designed MgH_(2) electrode on graphene could effectively alleviate the volume expansion,prevent the agglomeration of active substances,improve the electron transfer,and enhance the electrochemical performance of the anode material.As a result,a reversible capacity of 1214 mAh g^(−1) after 50 cycles is obtained.Significantly enhanced cycle life with a notable capacity of 597 mAh g^(−1) at a current density of 400 mA g^(−1) is delivered after 200 cycles.Further investigation on full cells also exhibits great application potential on ASSLIBs.
基金financially supported by the National Natural Science Foundation of China(Nos.51471149 and 51171168)the Public Project of Zhejiang Province(No.2015C31029)
文摘In order to improve the hydrogen storage properties of LiBH4-MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4-MgH2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH4-MgH2 system was investigated. The experimental results show that LiBH4-MgH2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320℃, and there is a long period of incubation time(around 220 min) for the occurrence of the second decomposition step even at high temperature of 450℃. It needs more than 10 h to complete the decomposition process and release around 9 wt% H2. After addition of 5 mol% NbF5, the starting decomposition temperature for the first dehydrogenation step is around 150℃, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.