The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))is acknowledged as a promising material for hydrogen storage due to its large hydrogen capacity(11.4 wt.%).However,the sluggish kinetics and poor reversibility make it difficu...The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))is acknowledged as a promising material for hydrogen storage due to its large hydrogen capacity(11.4 wt.%).However,the sluggish kinetics and poor reversibility make it difficult to be practically used.In this work,the hydrogen storage performances of 2LiBH_(4)+MgH_(2)have been significantly improved by a hybrid of bulk NbC and layered Nb_(4)C_(3)MXene(denoted as“Nb-C”).The 2LiBH_(4)+MgH_(2)+6 wt.%Nb-C can release 8.5 wt.%H_(2)within 30 min at 400℃and the dehy-drogenated composite can absorb 9.3 wt.%H_(2)within 30 min at 350℃and 7.5 MPa H_(2).The reversible dehydrogenation capacity maintains at 8.4 wt.%after 24 cycles,with a capacity retention ratio of 95.4%.By contrast,the undoped 2LiBH_(4)+MgH_(2)suffers from serious capacity degradation,with the capacity decreased dramatically to 3.5 wt.%after 3 cycles.Microstructural studies revealed that the doped com-posite has uniform particle and elemental distributions and possesses various multiphase interfaces of LiH/MgB_(2)/NbC/Nb_(4)C_(3),which is beneficial to hydrogen diffusion during the hydrogen uptake and release process.Theoretical studies by first principle calculation presented an extended bond length of the Mg-H and B-H bonds in the 2LiBH_(4)+MgH_(2)+NbC system,which may also explain the improved hydrogen storage properties of 2LiBH_(4)+MgH_(2)by addition of Nb-C.This work provides new insights into the role of transition metal carbides in regulating the Li-Mg-B-H hydrogen storage materials both experimentally and theoretically.展开更多
基金supported by the National Natural Science Foun-dation of China[Nos.22379030,52001079,and 52261038]the Sci-ence and Technology Department of Guangxi Zhuang Autonomous[No.GuiKeAD21238022]+1 种基金the Innovation Project of Guangxi Gradu-ate Education[No.YCBZ2023011]the high-performance com-puting platform of Guangxi University.
文摘The Li-Mg-B-H composite(2LiBH_(4)+MgH_(2))is acknowledged as a promising material for hydrogen storage due to its large hydrogen capacity(11.4 wt.%).However,the sluggish kinetics and poor reversibility make it difficult to be practically used.In this work,the hydrogen storage performances of 2LiBH_(4)+MgH_(2)have been significantly improved by a hybrid of bulk NbC and layered Nb_(4)C_(3)MXene(denoted as“Nb-C”).The 2LiBH_(4)+MgH_(2)+6 wt.%Nb-C can release 8.5 wt.%H_(2)within 30 min at 400℃and the dehy-drogenated composite can absorb 9.3 wt.%H_(2)within 30 min at 350℃and 7.5 MPa H_(2).The reversible dehydrogenation capacity maintains at 8.4 wt.%after 24 cycles,with a capacity retention ratio of 95.4%.By contrast,the undoped 2LiBH_(4)+MgH_(2)suffers from serious capacity degradation,with the capacity decreased dramatically to 3.5 wt.%after 3 cycles.Microstructural studies revealed that the doped com-posite has uniform particle and elemental distributions and possesses various multiphase interfaces of LiH/MgB_(2)/NbC/Nb_(4)C_(3),which is beneficial to hydrogen diffusion during the hydrogen uptake and release process.Theoretical studies by first principle calculation presented an extended bond length of the Mg-H and B-H bonds in the 2LiBH_(4)+MgH_(2)+NbC system,which may also explain the improved hydrogen storage properties of 2LiBH_(4)+MgH_(2)by addition of Nb-C.This work provides new insights into the role of transition metal carbides in regulating the Li-Mg-B-H hydrogen storage materials both experimentally and theoretically.
