Role of Local Carbon Structure Surrounding FeN4 Sites in Boosting the Catalytic Activity for Oxygen Reduction

Development of effective nonprecious metal and nitrogen codoped carbon catalysts for the oxygen reduction reaction (ORR) requires a fundamental understanding of the mechanisms underlying their catalytic activity. In this study, we employed the first-principles density functional theory calculations to predict some key parameters (such as activation energy for O–O bond breaking and free-energy evolution as a function of electrode potential) of ORR on three FeN4-type active sites with different local carbon structures. We find that the FeN4 site surrounded by eight carbon atoms and at the edge of micropores has the lowest activation energy (about 0.20 eV) for O–O bond breaking among the three FeN4-type active sites for promoting a direct four-electron ORR. Consequently, our computational results suggest that introduction of micropores in the nonprecious metal catalysts could enhance their catalytic activity for ORR through facilitating the formation of FeN4–C8 active sites with high specific activity.