Structural properties of Au/Cu₂O catalysts for electrochemical CO₂ reduction to C₂ products

Improving the selectivity towards multi-carbon products for the electrochemical reduction reaction of CO₂ (CO₂RR) with Cu-based catalysts remains a significant topic of scientific interest. It is known that using a secondary metal can provide some control over selectivity, with the structure of the bimetallic catalysts playing an important role in product distribution. In this study, we synthesized Au/Cu₂O catalysts via a precipitation method followed by galvanic replacement using varying Au concentrations. This approach enabled a systematic investigation of the restructuring of Cu₂O phases decorated with highly dispersed Au, Au-Cu alloys, and Au clusters and their impact on the catalytic activity. Among the tested catalysts, the Cu₂O catalyst with highly dispersed Au exhibited the highest Faradaic efficiency towards ethylene and ethanol. In situ X-ray absorption spectroscopy (XAS) and quasi-in situ X-ray photoelectron spectroscopy (XPS) measurements revealed that the presence of Au influenced the reduction of Cu₂O, where the catalyst with highly dispersed Au displayed the highest fraction of cationic Cu species. Furthermore, in situ X-ray diffraction (XRD) was employed to study the structural evolution of crystalline phases of the catalysts during CO₂RR, which suggests that significant restructuring and redispersion of Au takes place. This work highlights the relevance of in situ studies to understand the dynamic interplay between the structure and the catalytic behavior during the reaction.