The role of carbon in the hydrogen storage kinetics of lithium metal hydrides

A feasible solution to the problem of urban pollution is hydrogen propelled zero-emission vehicles. The US Department of Energy (DoE) has set the target of 6.5 wt% of H₂ storage capacity and a volumetric energy density of 1.5 kWh/L at an operating temperature and pressure conditions of 50°C and 2.5 bar respectively by 2010.[1] The storage media being studied until now have not been able to successfully achieve these targets and therefore, a compact, light weight hydrogen-storage system for transportation is not available currently. Hydrogen storage is therefore the key enabling technology that should be significantly advanced in terms of performance and cost effectiveness if hydrogen is to become an important part of the world's energy economy. In the present work, fundamental studies of the processes involved in hydrogen adsorption and release by carbon beryllium-containing lithium hydrides are carried out, to enable the design of efficient hydrogen storage materials for transportation applications. This is obtained by studying geometric, energetic, and thermodynamic properties such as the enthalpy of formation ΔH _f of ionic metal hydrides Li(C_nBe_y)H _x and Li₂(C_nBe_y)H_x. Our results indicate that the presence of (C-Be) dopants in Li-H complexes, enhances the desorption kinetics of these compounds lowering the enthalpy of dehydrogenation tremendously.