Stabilization of Cu⁺ Sites in Cu₂O-PdO Heterostructures via Orbital Engineering for Enhanced Electrochemical CO₂ Reduction to Ethylene

Electrochemical CO₂ reduction to multicarbon products is vital for renewable fuels. While copper catalysts are effective for C₂₊ production, the instability of Cu⁺ species hinders long-term performance. The present study reports the development of a Cu₂O-PdO heterojunction and investigates the influence of an unoccupied orbital energy level regulation strategy on the stabilization of interfacial crystalline Cu₂O during the CO₂ reduction reaction (CO₂RR). The hybrid catalyst showed a significant improvement, with an 84% higher Faradaic efficiency for C₂H₄, and the catalyst lasted over 7 h, vastly outperforming the 2 h benchmark of Cu₂O. In-situ Raman, ex-situ XRD, and theoretical calculations reveal that the broadened d-orbital in interfacial PdO provides a lower energy level for electrons, which contributes to the stabilization of adjacent Cu⁺ ions, and the high active interface significantly lowers the energy barrier of the CO-CO dimerization step (2*CO → *OCCO) and enhances the selectivity and activity for CO₂RR to ethylene.