Manipulating the Coordination Environment of Cu Single Atoms via Regulating ZrO₂ Support Crystal Phases for Enhanced CO₂ Electroreduction

For electrochemical CO₂ reduction (ECR), high-precision manipulation of the single-atomic catalytic centers is significant and remains an issue. Here, we report a support crystal phase engineering (SCPE) strategy by regulating the crystal phase of the ZrO₂ support to modulate its interaction with Cu atomic centers, synergizing the coordination environment of Cu atoms and the local microenvironment for ECR. Specifically, tetragonal ZrO₂ (tZrO₂) supports a Cu₁O₃ structure, and the rich bridging O atoms at the tZrO₂ surface could serve as basic sites. In contrast, the monoclinic ZrO₂ (mZrO₂) forming a Cu₁O₄ structure has weak basicity. The Cu₁O₃-tZrO₂ site displays a high activity for ECR to methane, with 3.16 (FE_CH₄) and 2.54 (<i>j</i>_CH₄) times higher than those of the Cu₁O₄-mZrO₂ counterpart. Density functional theory (DFT) and attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveal that the dynamic *OH on Cu₁O₃-tZrO₂ helps to significantly lower the Gibbs free-energy change (Δ<i>G</i>) for the rate-determining step (RDS). The rich basic sites on tZrO₂ could also facilitate the adsorption and activation of CO₂ and create an H₂O-expelling local microenvironment to suppress the competing hydrogen evolution reaction. Our work demonstrates a facile strategy to simultaneously manipulate the coordination environment of the active centers and the local microenvironment for the catalytic reaction.