Transition metal decorated borazine complex for hydrogen storage and unfavourable consequence of spin shift for hydrogen storage on Ti-decorated borazine: A DFT study

Density functional theory calculations have been carried out using hybrid B3PW91-functional for investigating hydrogen storage over Ti, Cr, and Fe doped borazine. The natural bond order and partial density of states analysis executed over ground (triplet) and excited (quintet) spin state of Ti-B3N3H6 revealed that the extent of hybridization between 4s and 3d-orbitals of Ti is significantly different in the two spin states. Presence of borazine results in the reduction of transition energy from triplet to quintet state of Ti and hence lead to easy accessibility to higher spin state. The binding energy for single hydrogen molecule in the quintet state of Ti-B3N3H6 is found to be less as compared to triplet state of the same. The overall hydrogen storage capability of Ti-B3N3H6 in quintet state is estimated to be half as compared to its triplet state and is thus unfavourable for hydrogen storage. Thermo-chemistry calculations recommend Ti-decorated over triplet state borazine complex as attractive candidate for hydrogen storage up to 400 K. The nature of interaction of hydrogen with Ti-B3N3H6 has also been investigated using many-body interaction energy calculations.