Tuning ORR on Graphene-MN4 Single-Atom Sites via 2D TMD Coupling

Abstract

Transition-metal single-atom sites have emerged as highly efficient oxygen reduction reaction (ORR) electrocatalysts owing to their maximized atom utilization and tunable electronic structures, while two-dimensional transition-metal chalcogenides (RX2) provide an effective platform for interfacial electronic modulation. In this work, density functional theory calculations are used to investigate the structural stability, electronic properties, and ORR activity of MN4 centers (M = Fe, Co, Mn) supported on RX2 substrates (R = Mo, W; X = S, Se, Te). Substrate coupling induces net electron transfer from the MN 4 centers to the RX2 support, reorganizing the 3d states and modulating both the d-band center and work function. To compare different slab models, the absolute d-band center is introduced as a unified descriptor, which strongly correlates with metalsite electron transfer and the binding strength of key intermediates (O* and OH*). This descriptor quantifies the extent to which substrate coupling weakens the adsorption of ORR intermediates and thereby serves as a useful indicator of the resulting change in ORR overpotential. These results establish a clear connection between interfacial charge transfer and the adsorption of reaction intermediates, providing a practical guideline for the rational design of 2D-material-supported single-atom catalysts.