Potential-Gated Transient Zn Single Adatoms on the Inverse Zn ₁ O <i> _x </i> /Cu Catalyst Steer Efficient Electroreduction of CO ₂

The inverse ZnO x /Cu catalysts exhibit exceptional activity for the electrochemical CO 2 reduction reaction (eCO 2 RR). 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 Zn 1 O x /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 CO 2 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.