Abstract

Electrochemical reduction of carbon dioxide, if powered by renewable electricity, could serve as a sustainable technology for carbon recycling and energy storage. Among all the products, ethanol is an attractive liquid fuel. However, the maximum faradaic efficiency of ethanol is only approximate to 10 % on polycrystalline Cu. Here, CuZn bimetallic catalysts were synthesized by in situ electrochemical reduction of ZnO-shell/CuO-core bi-metal-oxide. Dynamic evolution of catalyst was revealed by STEM-EDS mapping, showing the migration of Zn atom and blending between Cu and Zn. CuZn bimetallic catalysts showed preference towards ethanol formation, with the ratio of ethanol/ethylene increasing over five times regardless of applied potential. We achieved 41 % faradaic efficiency for C2+ liquids with this catalyst. Transitioning from H-cell to an electrochemical flow cell, we achieved 48.6 % faradaic efficiency and -97 mA cm(-2) partial current density for C2+ liquids at only -0.68 V versus reversible hydrogen electrode in 1 m KOH. Operando Raman spectroscopy showed that CO binding on Cu sites was modified by Zn. Free CO and adsorbed *CH3 are believed to combine and form *COCH3 intermediate, which is exclusively reduced to ethanol.

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