Cu₂₊₁O/CuO_x heterostructures promote the electrosynthesis of C₂₊ products from CO₂

Manipulating the oxidation state of Cu catalysts can significantly affect the selectivity and activity of electrocatalytic carbon dioxide reduction (CO₂RR). However, the thermodynamically favorable cathodic reduction to metallic states typically leads to catalytic deactivation. Herein, a defect construction strategy is employed to prepare crystalline/amorphous Cu₂₊₁O/CuO_x heterostructures (c/a-CuO_x) with abundant Cu⁰ and Cu^δ+ (0 < δ < 1) sites for CO₂RR. The C₂₊ Faradaic efficiency of the heterostructured Cu catalyst is up to 81.3%, with partial current densities of 406.7 mA·cm⁻². Significantly, real-time monitoring of the Cu oxidation state evolution by in-situ Raman spectroscopy confirms the stability of Cu^δ+ species under long-term high current density operation. Density functional theory (DFT) calculations further reveal that the adjacent Cu⁰ and Cu^δ+ sites in heterostructured c/a-CuO_x can efficiently reduce the energy barrier of CO coupling for C₂₊ products.