Grain Boundary-Derived Cu⁺ /Cu⁰ Interfaces in CuO Nanosheets for Low Overpotential Carbon Dioxide Electroreduction to...

Electrochemical CO₂ reduction reaction can be used to produce value-added hydrocarbon fuels and chemicals by coupling with clean electrical energy. However, highly active, selective, and energy-efficient CO₂ conversion to multicarbon hydrocarbons, such as C₂ H₄ , remains challenging because of the lack of efficient catalysts. Herein, an ultrasonication-assisted electrodeposition strategy to synthesize CuO nanosheets for low-overpotential CO₂ electroreduction to C₂ H₄ is reported. A high C₂ H₄ Faradaic efficiency of 62.5% is achieved over the CuO nanosheets at a small potential of -0.52 V versus a reversible hydrogen electrode, corresponding to a record high half-cell cathodic energy efficiency of 41%. The selectivity toward C₂ H₄ is maintained for over 60 h of continuous operation. The CuO nanosheets are prone to in situ restructuring during CO₂ reduction, forming abundant grain boundaries (GBs). Stable Cu⁺ /Cu⁰ interfaces are derived from the low-coordinated Cu atoms in the reconstructed GB regions and act as highly active sites for CO₂ reduction at low overpotentials. In situ Raman spectroscopic analysis and density functional theory computation reveal that the Cu⁺ /Cu⁰ interfaces offer high *CO surface coverage and lower the activation energy barrier for *CO dimerization, which, in synergy, facilitates CO₂ reduction to C₂ H₄ at low overpotentials.