Fe、Co和Ni掺杂LiBH_4放氢性能的第一性原理研究

Dehydrogenation Characteristics of Fe-,Co- and Ni-doped LiBH_4: a Comparative First-Principles Study

本工作旨在借助基于密度泛函理论的第一性原理计算来考察过渡金属元素Fe、Co、Ni掺杂LiBH_4的放氢性能。研究表明,Fe、Co、Ni掺杂有效提高了LiBH_4的放氢能力,这与掺杂体系B-H共价作用及Li-B/H离子作用的减弱,尤其是Fe/Co/Ni-B键的形成有关。体系Li7MB8H_32(M=Li、Fe、Co、Ni)的氢解离能与中心金属M的电负性负相关,即金属M的电负性越高,体系的氢解离能越小。与Fe、Co掺杂体系相比,具有较低金属占位能及较小氢解离能的Ni掺杂体系表现出良好的放氢特性。本研究从模拟计算的角度证实,利用高电负性金属(相对Li)与LiBH_4复合是实现LiBH_4"失稳"的一种有效方式。

This work involves a comparative first-principles calculation based on the density functional theory in order to provide a new insight into dehydrogenation characteristics of the transition metal( Fe,Co,Ni) doped LiBH4. Results showed that Fe,Co or Ni doping all can effectively improve the dehydrogenation performance of LiBH4 due to the weaker covalent bonding interaction between B-H and ionic bonding interaction between Li-B/H,especially the formation of Fe/Co/Ni-B bonds. For Li7MB8H32( M = Li,Fe,Co,Ni) systems considered here,dehydrogenation energies are negatively correlated with electronegativity of metal M,i. e. an increase in electronegativity of metal M leads to a decrease of the system’s dehydrogenation energy. Compared to Fe-and Co-doped systems,Ni-doped system,which has relatively low occupation energy and dehydrogenation energy according to the calculation,displays a satisfactory dehydrogenation performance. Our work has indicated from the perspective of computational simulation that combining LiBH4 with a metal element more electronegative than Li is an effective approach to the destabilization of LiBH4.