Understanding the restructuring and degradation of oxide-derived copper during electrochemical CO2 reduction

Abstract

Renewable energy produced through electrochemical CO2 reduction is promising for mitigating the energy crisis and environmental issues. Notably, oxide-derived copper (OD-Cu) has attracted considerable attention owing to its unique ability to catalyze CO2 electroreduction to >2e− products, especially C2+ products, which are the key feedstocks for the chemical process. However, Cu under operating conditions usually leads to structure reconstruction and degradation, which hinders understanding the origin of its activity. Understanding the restructuring and degradation of OD-Cu catalyst to form C2+ products is critical for understanding the active sites and, thus for designing effective and durable catalysts for CO2 reduction. This paper describes that Cu defect sites are easily dissolved during electrochemical CO2 reduction, and the presence of defect sites is strongly related to the catalytic performance of C2+ products. Here, the C2+ products Faradaic efficiency (FE) of OD-Cu decreased from 39.4% at 1 h to 26.0% at 5 h at −1.5 V vs. RHE, along with a decrease in low-coordinated defect sites. The low-coordinated defect sites facilitate CO adsorption and help to increase the CO coverage, thus promoting CO–CO coupling. The decrease in the number of defect sites and activity degradation is circumvented by promoting the Cu redeposition process. The C2+ products FE of OD-Cu can be maintained at ca. 47.2% without an obvious decrease in CO2-saturated 0.1 M KHCO3 with 1 mM Cu2+. The results of this study help in understanding the activity of OD-Cu and reveal its deactivation mechanism. This knowledge will aid in designing highly active and stable catalysts for CO2 reduction.