Identifying Iron-Nitrogen/Carbon Active Structures for Oxygen Reduction Reaction under the Effect of Electrode Potential

Transition-metal-nitrogen/carbon (TM-N/C) materials are promising alternatives to Pt-based oxygen reduction reaction (ORR) electrocatalysts of fuel cells. Identifying the highly active sites is the prerequisite for the design of high-performance electrocatalysts, in which the density functional theory (DFT) calculation is an important tool. However, the DFT simulation was usually conducted with a charge-neutral model, which is far away from the working condition, that is, under certain potentials. Herein, by using the DFT method with the explicit consideration of electrode potential, we systematically compared the activities of the Fe-N/C moieties previously proposed in the literature and identified the best one. This study not only demonstrates the significance of the electrode potential in computational electrochemistry but also suggests a feasible experimental strategy to increase the ORR performance of Fe-N/C electrocatalysts by creating edges defects and coordinating with the axial ligands on the Fe center, which is of practical significance for exploring the advanced non-precious-metal-based ORR electrocatalysts and related devices.