Dynamic determination of Cu+ roles for CO2 reduction on electrochemically stable Cu2O-based nanocubes

Abstract

Copper (Cu), as the most important and efficient catalyst, has been widely studied for electrochemically reducing carbon dioxide (CO₂) into multi-carbon (C₂₊) products. However, the roles of Cu⁺ species in CO₂ reduction are debatable due to the instabilities of all the reported Cu oxides under negative potentials. Here, for the first time, we fabricated an electrochemically stable Cu₂O catalyst. In situ Raman spectroscopy determines that, with the protection of ligands, the Cu⁺ species are resistant to the negative potentials and remain unchanged during CO₂ reduction. We find that stable Cu₂O shows a high C₂ Faraday efficiency (FE) of 73%, 1.5× higher than that of common Cu₂O, which reduces to metallic Cu during the CO₂ reduction, suggesting that the Cu⁺ species promote C–C coupling. Further, we coat the ligand-stabilized Cu₂O nanocubes with AgO_x clusters, which achieves an increase in ethylene FE from 35% to 50% under a current density of 150 mA cm⁻².