Adapting Atomic Configuration Steers Dynamic Half-Occupied State for Efficient CO₂ Electroreduction to CO

Electronic structures stand at the center to essentially understand the catalytic performance and reaction mechanism of atomically dispersed transition-metal-nitrogen-carbon catalysts (ADTCs). However, under realistic electrocatalytic conditions, the dynamic electronic disturbance at metal centers originating from complicated interactions with microenvironments is commonly neglected, which makes a true structure-property correlation highly ambiguous. Here, we employ operando time-resolved X-ray absorption spectroscopy to delve deeply into dynamic electronic behaviors of a family of transition-metal centers that are observed to adaptively vary in the metal-ligand configuration during the CO₂ electroreduction reaction. We identify dynamic electronic/geometric configuration and d-orbital occupation under working conditions, demonstrating an unprecedentedly precise activity descriptor, i.e., dynamic axial d_z² electron, for the CO₂-to-CO conversion. Direct results validate that the half-occupied state suggests the optimum binding behaviors with intermediates, significantly promoting CO production, which has been demonstrated by a significant kinetics enhancement of 1 to 2 orders of magnitude as compared with fully occupied and unoccupied states. This work presents the first empirical demonstration for a real correlation between the dynamic electronic/geometric configuration and catalytic kinetics in ADTCs, paving a new way for modulating catalysts and designing highly efficient reaction pathways.