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

Targeting acetate as a CO 2 electroreduction reaction (CO 2 RR) 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 C 1 products, or other C 2+ products, and acetate is usually presented as a byproduct. Herein, the effect of CuO x catalysts with different Cu(II)/Cu(I) ratios on the electrocatalytic reduction of CO 2 to acetate was investigated. The 350-CuO/Cu 2 O catalyst with the Cu(II)/Cu(I) ratio of 1.23 achieved a C 2+ Faradaic efficiency (FE C 2+ ) of 50.18 ± 1.45% and an acetate Faradaic efficiency (FE acetate ) of 35.78 ± 0.42% at a potential of −0.9 V versus the reversible hydrogen electrode in an H-type electrolysis cell, outperforming CuO x catalysts with other Cu(II)/Cu(I) ratios. Additionally, 350-CuO/Cu 2 O maintained high catalytic performance stability during the catalytic process, resulting in no significant decay of FE acetate 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 *OOCCH 3 key intermediates, thereby accelerating the conversion of CO 2 to acetate and suppressing the competitive hydrogen evolution reaction. This work provides fresh insight into enhance the selectivity of acetate based on CuO x catalysts.