Trace Ionic Liquid-Assisted Orientational Growth of Cu₂ O (110) Facets Promote CO₂ Electroreduction to C₂ Products

Cu₂ O has great advantages for CO₂ electroreduction to C₂ products, of which the activity and selectivity are closely related to its crystal facets. In this work, density functional theory calculation indicated that the (110) facets of Cu₂ O had a lower energy barrier for the C-C coupling compared to the (100) and (111) facets. Therefore, Cu₂ O(110) facets were successfully synthesized with the assistance of trace amounts of the ionic liquid 1-butyl-3-methylimidazolium ([Bmim]BF₄ ) by a sample wet-chemical method. A high faradaic efficiency of 71.1 % and a large current density of 265.1 mA cm^-2 toward C₂ H₄ and C₂ H₅ OH were achieved at -1.1 V (vs. reversible hydrogen electrode) in a flow cell. The in situ and electrochemical analysis indicated that it possessed the synergy effects of strong adsorption of *CO₂ and *CO, large active area, and excellent conductivity. This study provided a new way to enhance the C₂ selectivity of CO₂ electroreduction on Cu₂ O by crystal structure engineering.