Crystallinity-Directed In Situ Reconstruction of Cu–Al Oxides Yielding Tunable Cuδ+ Sites for Electrochemical CO2-to-C2+ Conversion

During the electrochemical CO2 reduction reaction (CO2RR), copper catalysts continuously undergo structural evolution, which is less controllable, and its impact on the product distribution of CO2RR remains unclear. Here, crystallinity-tunable Cu-Al mixed metal oxide (CuAl-MMO-T) precatalysts were first synthesized via layered double hydroxide calcination. These precatalysts subsequently underwent in situ electrochemical reconstruction to form active CuAl-MMO-TR catalysts with tailored Cuδ+ valence states. The moderately crystalline-derived CuAl-MMO-600R achieves a C2+ Faradaic efficiency of 76.8% with 44.6% ethylene selectivity at -300 mA·cm-2, outperforming both its low- and high-crystallinity counterparts. In situ Raman and density functional theory showed that residual Al species stabilize Cu+ active sites via strong electronic interactions, while oxygen vacancies promote *CO adsorption and OH- enrichment, synergistically lowering the C-C coupling energy barrier. Furthermore, system integration assisted by the glycerol oxidation reaction reduces the full-cell voltage by 17%, enabling simultaneous CO2-to-C2+ conversion and biomass-derived chemical production. This crystallinity-directed reconstruction strategy provides a pathway to tailoring CO2RR electrocatalysts and controlling the product selectivity.