B,N-Codoped graphene as catalyst for the oxygen reduction reaction: Insights from periodic and cluster DFT calculations.

A comprehensive theoretical study of the oxygen reduction reaction (ORR) over B,N-codoped graphene has been carried out in the framework of DFT using two different approaches based on periodic or cluster models. The comparison and integration of the information provided by the two approaches allow achieving a more complete description of the studied phenomena, combining the advantages of both models. On one hand, the analysis of the structure, stability, and electronic properties of this catalyst permits to identify and characterize the active sites and provides insights into the origin of its high catalytic activity that should be found in the synergistic coupling of the opposite effects of the two B and N heteroatoms used as dopants. On the other hand, the study of the reaction mechanisms evidences that the process is thermodynamically favorable due to the overall high exothermicity, and that the 4e- transfer is the favorite ORR pathway, being the OH hydrogenation the rate-determining step. Overall, all the reported results clearly underline the superior catalytic activity of B,N-codoped graphene toward this reaction.