Beyond Activity: Unraveling Degradation Mechanisms and Engineering Stability in Transition Metal–Nitrogen–Carbon Single‐Atom Oxygen Reduction Reaction Catalysts for Alkaline Media

Single‐atom catalysts (SACs) featuring transition metals coordinated with nitrogen on carbon supports (TM–N–C) have emerged as formidable alternatives to noble‐metal electrocatalysts for the oxygen reduction reaction (ORR) in alkaline media. Although these materials exhibit exceptional atom utilization and high intrinsic activity, their practical implementation is often hindered by complex performance decline mechanisms. This review provides a comprehensive analysis of the degradation pathways prevalent in alkaline environments, specifically metal active site blockage, demetallation, and carbon support corrosion. A critical examination is presented regarding how intermediate poisoning, the pH‐dependent “mechanical switching” of active centers, and the ORR‐induced dissolution of metal cations lead to significant kinetic losses. Beyond the analysis of degradation, the review systematically explores improvement strategies designed to enhance ORR performance. Assessment is provided on how multiple active site engineering, coordination environment tuning, and heteroatom doping can be leveraged to manipulate the spin state, electronic density, and unsaturated coordination of the metal center. By correlating these structural descriptors with catalytic indicators such as turnover frequency and Tafel slopes, the review identifies key parameters for the rational design of high‐performance TM–N–C SACs. Finally, the roles of support structure engineering and composite structures are discussed.