Zero-Gap Electrolyzers Accelerate Reconstruction of Cu₂O-Derived Catalysts under CO₂ Reduction

To scale carbon dioxide reduction (CO2R), establishing a structure–property–performance relationship of the catalyst under the reaction conditions is a priority. Particularly in membrane electrode assembly (MEA) electrolyzers, knowledge about the valence state and coordination environment of the catalyst is of value yet limited. We developed an MEA electrolyzer that utilizes X-ray absorption spectroscopy to investigate the structural evolution of Cu2O-derived catalysts under CO2R and compare the same catalysts in a flow cell. Additionally, we study the influence of CO reduction and incorporating Ag on the reconstruction of the catalyst. We find that the strong reduction environment in the MEA and feeding CO leads to reconstruction of Cu2O particles, favoring higher coordination and lower oxidation states, which coincides with a shift in the reaction selectivity from C2+ to hydrogen. Conversely, incorporating small amounts of Ag in the catalyst restricts the reconstruction. These findings advocate for in situ studies in zero-gap electrolyzers.