Discovery of New Dual Cation Metal Ammine Borohydrides: A Computational Study

Abstract

World’s growing energy need is mostly reliant upon fossil fuels. Fossil fuels are considered to be non-renewable energy sources because it needs million years to form and reserves are being depleted much more faster than new reserves are being made. Usage of fossil fuels comes with harmful consequences. It is responsible for 20 % of global warming pollution. To avoid these harmful effects, new energy sources must be discovered. As an alternative to fossil fuels, hydrogen can be used for energy needs and it has a lot of benefits over fossil fuels such as being environmentally friendly, carrying high energy content and being renewable. To use hydrogen as an energy source instead of fossil fuels, some challenging problems must be solved. One of them is hydrogen storage. Hydrogen can be stored as gas or liquid but these types of storage are not so efficient for widespread use. A more convenient way is to store hydrogen in the form of solid. For this purpose, metal borohydrides and ammines can be used due to their high gravimetric and volumetric densities. To decompose hydrogen, metal borohydrides requires very high temperatures and this situation can be moderated by mixing them with ammines. To achieve this goal, in this study we designed dual-cation ammine metal borohydrides (AMBs) in the form of LiSc(BH4)4(NH3)x (x = 2, 3) using an approach which combines crystal structure prediction with density functional theory computations.