Switching CO<sub>2</sub> Electroreduction toward Ethanol by Delocalization State-Tuned Bond Cleavage
Zhengzheng Liu, Song Lu, Ximeng Lv, Mingtai Liu, Qianyou Wen, Linping Qian, Haozhen Wang, Maoyin Wang, Qing Han, Gengfeng Zheng
Abstract
The electrochemical CO 2 reduction reaction by copper-based catalysts features a promising approach to generate value-added multicarbon (C 2+ ) products. However, due to the unfavored formation of oxygenate intermediates on the catalyst surface, the selectivity of C 2+ alcohols like ethanol remains unsatisfactory compared to that of ethylene. The bifurcation point (i.e., the CH 2 ═CHO* intermediate adsorbed on Cu via a Cu–O–C linkage) is critical to the C 2+ product selectivity, whereas the subsequent cleavage of the Cu–O or the O–C bond determines the ethanol or ethylene pathway. Inspired by the hard–soft acid–base theory, in this work, we demonstrate an electron delocalization tuning strategy of the Cu catalyst by a nitrene surface functionalization approach, which allows weakening and cleaving of the Cu–O bond of the adsorbed CH 2 ═CHO*, as well as accelerating hydrogenation of the C═C bond along the ethanol pathway. As a result, the nitrene-functionalized Cu catalyst exhibited a much-enhanced ethanol Faradaic efficiency of 45% with a peak partial current density of 406 mA·cm –2, substantially exceeding that of unmodified Cu or amide-functionalized Cu. When assembled in a membrane electrode assembly electrolyzer, the catalyst presented a stable CO 2 -to-ethanol conversion for >300 h at an industrial current density of 400 mA·cm –2 .