Potential-Gated Transient Zn Single Adatoms on the Inverse Zn1Ox/Cu Catalyst Steer Efficient Electroreduction of CO2.

The inverse ZnOx/Cu catalysts exhibit exceptional activity for the electrochemical CO2 reduction reaction (eCO2RR). However, identifying the atomistic origin of their structure-activity relationship is hindered by the dynamic nature of the active sites under operando conditions. Herein, we combine grand-canonical ensemble density functional theory and explicit-solvent ab initio molecular dynamics to reveal a potential-gated transient single-adatom mechanism in the atomically dispersed inverse Zn1Ox/Cu catalyst. We demonstrate that the O-coordinated Zn sites on Cu surfaces undergo in situ reduction at cathodic potentials, transforming into transient metallic Zn single adatoms, which are robustly stabilized via Zn-Cu electronic coupling and interfacial solvent confinement. This transient single adatom structurally preorganizes the chemisorbed CO2 intermediate via asymmetric polarization and redirects protonation toward a solvent-exposed oxygen, thereby creating a geometry-enabled pathway unavailable on pristine Cu or with embedded Zn single atoms. This distinct reaction geometry lowers the rate-determining protonation barrier while avoiding the promotion of the competing hydrogen evolution reaction. These findings suggest electrochemically gated transient single adatoms as a design strategy for highly efficient and selective electrocatalysis.