Enhancing CO2 Electroreduction Performance through Si-Doped CuO: Stabilization of Cu+/Cu0 Sites and Improved C2 Product Selectivity

Abstract

Cu-based catalysts leveraging Cu⁺/Cu⁰ active sites have emerged as pivotal for synthesizing essential hydrocarbons and alcohols in electrochemical CO₂ reduction, such as ethylene and ethanol (C₂ products). However, the dynamic reduction of Cu⁺ to Cu⁰ during electroreduction leads to site instability, resulting in diminished efficiency for CO₂ conversion to C₂ products. Herein, we introduced Si into CuO by the selective dissolution method, engendering Cu–O–Si units to stabilize the Cu⁺/Cu⁰ sites. The catalyst manifested good activity in CO₂ electroreduction with an elevated Faradaic efficiency for C₂ products reaching 81.9% at −100 mA/cm². After ten cycles of electrochemical testing, the Cu⁺/Cu⁰ sites and performance exhibited no signs of degradation. The Si incorporation significantly improved the hybridization of O 2p and Cu 3d orbitals, thereby reinforcing the Cu–O bonds and stabilizing the Cu⁺/Cu⁰ sites, which was critical in promoting C–C coupling via decreasing the energy barriers for *OCCO formation and enhancing C₂ product selection. The active Cu⁺ cations with unsaturated coordination contributed to the reaction stabilization, thereby improving the preservation of Cu₂O metastable state.