Ti-Decorated BC4N Sheet: A planar Nanostructure for High-Capacity Hydrogen Storage

A planar sheet of carbon (graphene) or isoelectronic boron nitride has been decorated by Ti atoms for a high-capacity hydrogen storage material. Due to charge transfer, the Ti becomes cationic and helps to adsorb hydrogen in the molecular form. The principal bottleneck for using such a system for efficient H storage is the problem of metal clustering on the surface. Using the first-principles density functional theory calculations, we show that clustering of Ti atoms can be avoided by using a composite BC4N planar sheet that is obtained through chemical modification of the graphene surface by systematically replacing C atoms by B and N atoms. This Ti@BC4N system shows hydrogen storage capacity with a reasonably high gravimetric efficiency (similar to 8.4 wt %). Further, using ab initio molecular dynamics simulation, we show that this system is stable at 300 K, while desorption starts at similar to 500-600 K, which is lower compared to that of conventional graphene or BN planar structures.