Organizational\nand Mechanistic Modulation of ORR/OER\nActivity in M<sub>1</sub>M<sub>2</sub>–N–C Bimetallic\nCatalysts

The M<sub>1</sub>M<sub>2</sub>–N–C (where,\nM represents\nelements such as Mn, Fe, Co, Ni, Cu, and Zn) bimetallic electrocatalysts\nhave garnered significant attention for their applications in the\noxygen reduction reaction (ORR) and oxygen evolution reaction (OER).\nHowever, the design of catalytic sites remains unclear, which limits\nfurther advancements. In this study, we employed high-throughput first-principles\ncalculations to demonstrate that the ORR/OER catalytic activity of\nM<sub>1</sub>M<sub>2</sub>–N–C can be regulated through\norganizational and mechanistic modulation. A systematic comparison\nof the ORR/OER activities of nearly 100 catalytic sites in FeNi–N–C\nrevealed that bridged and unbridged bimetallic atoms exhibit distinct\nORR/OER catalytic performances. Specifically, the bimetallic bridged\nconfigurations follow associative or dissociative reaction pathways,\nwhereas the unbridged configurations adhere solely to the dissociative\npath. Bridging enhances the ORR/OER catalytic activity of FeNi–N–C.\nAdditionally, atomic substitution can effectively control the reaction\npathway of bridged configurations and allow them to follow the dissociative\nmechanism. Notably, replacing Ni with Co can reduce the theoretical\nORR/OER overpotentials of the bridged configuration under the dissociative\nmechanism to 0.11/0.13 V, which makes it a bifunctional catalyst.\nFurthermore, the integrated crystal orbital Hamilton population is\nproposed as an electronic descriptor that characterizes the selectivity\nof the ORR/OER reaction mechanism and the performance of M<sub>1</sub>M<sub>2</sub>–N–C. This work provides insights into\nthe ORR/OER activity of M<sub>1</sub>M<sub>2</sub>–N–C\ncatalysts and paves the way for future designs and catalytic improvements.