| Abstract Scope |
Single-atom catalysts (SACs) and M–N–C materials are promising electrocatalysts for oxygen reduction, where they can catalyze either the four-electron pathway to H₂O or the two-electron pathway to H₂O₂. Their performance, however, is governed by ensembles of metal–nitrogen sites formed during high-temperature synthesis rather than by a single well-defined active site. Here, we use density functional theory to investigate the kinetic and thermodynamic stability of M–Nₓ motifs during synthesis and under electrochemical operating conditions, focusing on selective O₂ reduction to H₂O₂. Our calculations show how nitrogen coordination controls metal-site formation, resistance to particle formation, and catalytic reactivity by tuning OOH binding. Optimal activity and selectivity arise from a narrow range of local coordination environments that balance stability and reactivity. By comparing modeling results with experiments, we link synthesis-dependent active-site distributions to catalytic performance and provide design principles for complex SAC ensembles. |