Recent Work
1.

Characteristic features of the d-band in electronic structure of transition metals have been quite effective as descriptors of their catalytic activity towards oxygen reduction reaction (ORR). With the promise of graphene-based materials to replace precious metal catalysts, descriptors of their chemical activity are much needed. Here, we propose a site-specific electronic descriptor based on the pz (π) orbital occupancy and its contribution to electronic states at the Fermi level. We identify simple structural descriptors and develop a linear predictive model to precisely estimate adsorption free energies of OH (ΔGOH) at various sites of doped graphene, and demonstrate it through prediction of the most optimal site for catalysis of ORR. These structural descriptors, essentially the number of ortho, meta and para sites of N/B doped graphene sheet, can be extended to other doped sp2 hybridized systems, and greatly reduce the computational effort in estimating ΔGOH and site-specific catalytic activity..

2.

Graphite, a sp2 hybridized layered material is used as an anode material in commercial Lithium ion batteries (LIB’s). It is desirable to improve the Li/C ratio in the sp2 hybridized carbon allotropes to increase the specific energy capacity. Using First-principles calculations bulk Phagraphene (contains penta-, hepta- and hexa ring) an example of sp2 hybridized carbon allotropes is identified as a potential high capacity anode material for rechargeable LIB’s. The Li adsorption site preference is attributed to the combined effect of the pz electrons of the carbon atoms constituting a ring. It is found that the Li diffusion is favoured during both adsorbed and intercalated state. Bulk-Phagraphene shows desirable negative formation energy, high specific capacity of 558 mAh/g, and stable positive open circuit voltage profile for high Li intercalation. Overall the asymmetry in the pz electron occupancies of the distinct carbon atoms in Phagraphene is identified to be a major contributing factor for the higher activity of Phagraphene as compared to the graphene. This indicates that we can tune the property of sp2 based carbon structures by changing the π electron environments.