Organizational and Mechanistic Modulation of ORR/OER Activity in M1M2–N–C Bimetallic Catalysts

Abstract

The M₁M₂–N–C (where, M represents elements such as Mn, Fe, Co, Ni, Cu, and Zn) bimetallic electrocatalysts have garnered significant attention for their applications in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the design of catalytic sites remains unclear, which limits further advancements. In this study, we employed high-throughput first-principles calculations to demonstrate that the ORR/OER catalytic activity of M₁M₂–N–C can be regulated through organizational and mechanistic modulation. A systematic comparison of the ORR/OER activities of nearly 100 catalytic sites in FeNi–N–C revealed that bridged and unbridged bimetallic atoms exhibit distinct ORR/OER catalytic performances. Specifically, the bimetallic bridged configurations follow associative or dissociative reaction pathways, whereas the unbridged configurations adhere solely to the dissociative path. Bridging enhances the ORR/OER catalytic activity of FeNi–N–C. Additionally, atomic substitution can effectively control the reaction pathway of bridged configurations and allow them to follow the dissociative mechanism. Notably, replacing Ni with Co can reduce the theoretical ORR/OER overpotentials of the bridged configuration under the dissociative mechanism to 0.11/0.13 V, which makes it a bifunctional catalyst. Furthermore, the integrated crystal orbital Hamilton population is proposed as an electronic descriptor that characterizes the selectivity of the ORR/OER reaction mechanism and the performance of M₁M₂–N–C. This work provides insights into the ORR/OER activity of M₁M₂–N–C catalysts and paves the way for future designs and catalytic improvements.