New insights into influences of initial oxidization states on dynamic reconstruction of Cu catalysts and C–C coupling in CO2 reduction

Abstract

Cu-based catalysts hold enormous potential for electrocatalytic CO₂ reduction toward value-added C₂₊ products, and surface reconstruction commonly happens under operating CO₂ reduction conditions. Understanding Cu reconstruction is thus of utmost importance as it directly affects surface sites and catalytic pathways. Here, we report on how the initial oxidization states of Cu catalysts influence their in situ dynamic reconstruction and crucial factors determining C–C coupling through comprehensive ex situ/in situ microscopic and spectroscopic methods. We demonstrate that the spontaneous oxidization/reduction of the Cu surface occurs during CO₂ reduction, resulting in the dynamic formation of CuO_x species. Compared to metallic Cu, Cu oxides leave more oxygen residues on the Cu surface due to the mild electrochemical reduction process. Such a situation leads to a longer time required to reach the steady-state oxidization/reduction of CuO_x species and less concentration of CuO_x on the oxide-derived Cu surface than the metallic one. Moreover, we reveal that the in situ formed CuO_x species play a more significant role in promoting C–C coupling than commonly recognized factors, such as surface oxygen residues, local pH, and CO coverage. This work provides insights into mechanisms of metal surface reconstruction and motivates the design of advanced catalysts in electrocatalysis.