In situ stabilization of Cu⁺ for CO₂ Electroreduction via Environmental-molecules-induced ZnO_1-x shield.

Abstract

Electrochemical CO₂-to-ethanol conversion is challenged by sluggish C-C coupling kinetics and wide products distribution. Although Cu⁺ has been demonstrated to enhance multi-carbon (C₂₊) formation, the stabilization of Cu⁺ under reduction conditions is difficult. Here, we report a hydrogen-ethanol pretreatment strategy to obtain Cu nanoparticles covered by highly dispersed and disordered ZnO_1-x clusters. Ethanol-induced ZnO_1-x redispersion gives rise to abundant Cu⁺ on the subsurface. The optimal catalyst delivers a 73.0% ethanol Faradaic efficiency (FE) and 86.0% total C₂₊ FE at -0.9 V, with a 2.3 mmol cm^-2 h^-1 ethanol formation rate and single-pass ethanol yield of 18.0%. The catalyst also exhibits stability beyond 500 h, attributed to the stabilization of Cu⁺ by the ZnO_1-x shield that requires a high energy barrier for lattice oxygen removal. In situ X-ray spectroscopy and calculations reveal a volcano relationship between Cu⁺ ratio in Cu species and ethanol FE. Optimal Cu⁺ density not only facilitates *OC-COH coupling but also optimizes the adsorption energy of *CH₂CH₂O on catalyst for ethanol electrosynthesis.