Zero-Gap Electrolyzers\nAccelerate Reconstruction of\nCu<sub>2</sub>O‑Derived Catalysts under CO<sub>2</sub> Reduction

To scale carbon dioxide reduction (CO<sub>2</sub>R),\nestablishing\na structure–property–performance relationship of the\ncatalyst under the reaction conditions is a priority. Particularly\nin membrane electrode assembly (MEA) electrolyzers, knowledge about\nthe valence state and coordination environment of the catalyst is\nof value yet limited. We developed an MEA electrolyzer that utilizes\nX-ray absorption spectroscopy to investigate the structural evolution\nof Cu<sub>2</sub>O-derived catalysts under CO<sub>2</sub>R and compare\nthe same catalysts in a flow cell. Additionally, we study the influence\nof CO reduction and incorporating Ag on the reconstruction of the\ncatalyst. We find that the strong reduction environment in the MEA\nand feeding CO leads to reconstruction of Cu<sub>2</sub>O particles,\nfavoring higher coordination and lower oxidation states, which coincides\nwith a shift in the reaction selectivity from C<sub>2+</sub> to hydrogen.\nConversely, incorporating small amounts of Ag in the catalyst restricts\nthe reconstruction. These findings advocate for <i>in situ</i> studies in zero-gap electrolyzers.