A Physically Grounded Descriptor Decoupling Intrinsic and External Contributions to CO ₂ Electroreduction over Single-Atom Catalysts

Descriptors that link the microscopic structure to macroscopic performance provide a foundation for rational catalyst design. However, most existing descriptors focus primarily on static intrinsic properties, limiting their ability to describe apparent activity under working conditions. Here, we propose a physically grounded descriptor for the potential-dependent electrocatalytic performance of single-atom catalysts (SACs) in CO 2 reduction. This descriptor captures the static electronic structure of SACs and their dynamic response to applied potential, explicitly decoupling and quantifying their respective contributions to the reaction thermodynamics and kinetics. By integrating this descriptor into a microkinetic framework, we establish a direct connection between readily accessible parameters and emergent catalytic behavior across a broad range of SACs under different potentials in excellent agreement with experimental measurements. Beyond predictive capability, it offers mechanistic insights into fundamental catalytic behavior, including quantifying the catalyst- and potential-dependent roles of intrinsic and external effects, group-dependent selectivity trends, valence-dependent potential response, dynamic restructuring of active sites, and the intrinsic trade-off among activity, selectivity, and stability. Overall, this physically interpretable descriptor decodes the structure–performance relation of SACs under operating conditions, where the insights revealed offer fundamental principles for future experimental discovery.