CO<sub>2</sub>-assisted formation of grain boundaries for efficient CO–CO coupling on a derived Cu catalyst

The electrochemical CO₂ reduction reaction (CO₂RR) on Cu catalyst holds great promise for converting CO₂ into valuable multicarbon (C₂₊) compounds, but still suffers poor selectivity due to the sluggish kinetics of forming carbon–carbon (C–C) bonds. Here we reported a perovskite oxide-derived Cu catalyst with abundant grain boundaries for efficient C–C coupling. These grain boundaries are readily created from the structural reconstruction induced by CO₂-assisted La leaching. Using this defective catalyst, we achieved a maximum C₂₊ Faradaic efficiency of 80.3% with partial current density over 400 mA cm⁻² in neutral electrolyte in a flow-cell electrolyzer. By combining the structural and spectroscopic investigations, we uncovered that the in-situ generated defective sites trapped by grain boundaries enable favorable CO adsorption and thus promote C–C coupling kinetics for C₂₊ products formation. This work showcases the great potential of perovskite materials for efficient production of valuable multicarbon compounds via CO₂RR electrochemistry.