CuO/Cu ₂ O Catalyst with Adjustable Cu(II)/Cu(I) for Selective CO ₂ Electroreduction to Acetate

Targeting acetate as a CO2 electroreduction reaction (CO2RR) end-product is a perspective to reform the current acetate industry. However, in current research, the selectivity of acetate is difficult to improve due to competitive reactions such as hydrogen evolution, the formation of C1 products, or other C2+ products, and acetate is usually presented as a byproduct. Herein, the effect of CuOx catalysts with different Cu(II)/Cu(I) ratios on the electrocatalytic reduction of CO2 to acetate was investigated. The 350-CuO/Cu2O catalyst with the Cu(II)/Cu(I) ratio of 1.23 achieved a C2+ Faradaic efficiency (FEC2+) of 50.18 ± 1.45% and an acetate Faradaic efficiency (FEacetate) of 35.78 ± 0.42% at a potential of −0.9 V versus the reversible hydrogen electrode in an H-type electrolysis cell, outperforming CuOx catalysts with other Cu(II)/Cu(I) ratios. Additionally, 350-CuO/Cu2O maintained high catalytic performance stability during the catalytic process, resulting in no significant decay of FEacetate over 32 h. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory calculations confirmed that the appropriate Cu(II)/Cu(I) ratio can optimize the energy barrier to generate *OCCOH and *OOCCH3 key intermediates, thereby accelerating the conversion of CO2 to acetate and suppressing the competitive hydrogen evolution reaction. This work provides fresh insight into enhance the selectivity of acetate based on CuOx catalysts.