Transition metal-N2P2 embedded graphene (TM-NPC) as single-atom catalyst for oxygen reduction reaction: a computational study

The sluggish kinetics of the oxygen reduction reaction (ORR) is a major hurdle for the development of efficient fuel cells. The conventional Pt based catalysts being very expensive, development of noble metal free catalysts for accelerating the kinetics of ORR is highly important. Here, we explored the transition metal (Fe, Co, Ni and Cu) decorated over the nitrogen and phosphorous co-doped graphene as a single-atom catalyst for ORR. Among the four metal decorated systems considered, oxygen molecule is found to strongly interact with only Fe and Co systems while it was too weak with the Ni and Cu systems. Both the Fe and Co decorated systems were systematically investigated for their activity towards ORR through the four-electron reduction path. From the free energies calculated for all the intermediate reactions of ORR, Fe-decorated system was found to have lower overpotential as compared to that of the Co-decorated system indicating the former one as a better catalyst for ORR.