Recent Design Strategies for M‐N‐C Single‐Atom Catalysts in Oxygen Reduction: An Entropy Increase Perspective

Abstract Recently, a diverse array of novel metal‐nitrogen‐carbon (M‐N‐C) single‐atom catalysts (SACs) have rapidly evolve, particularly in the realm of oxygen reduction reaction (ORR). Despite the plethora of proposed design and improvement strategies for SACs, a comprehensive review systematically compiling the components in M‐N‐C from a unified perspective is notably absent. For the first time, a thorough examination of each component in M‐N‐C is conducted, focusing on the perspective of entropy increase in the active sites of SACs. For the single M‐N 4 sites and the whole M‐N‐C system, an increase in entropy implies an elevated degree of disorder and chaos. Broadly, the entropy‐increasing modification of M (single mental sites) and guest groups entails an augmentation of chaos, with the most effective co‐catalytic synergy achieved by establishing multiple active sites through a “cocktail effect”. Concerning N (nitrogen and other heteroatoms) and C (carbon supports), the entropy increase modification induces heightened disorder, with symmetry breaking more likely to drive M‐N 4 toward adsorbing oxygen molecules to attain an equilibrium symmetric structure. All these innovative design strategies have led to a remarkable improvement in the ORR activity and stability and offer a guiding criterion for the future preparation of SACs.