Joint tuning the morphology and oxygen vacancy of Cu2O by ionic liquid enables high-efficient CO2 reduction to C2 products

The electrochemical CO2 reduction to multi-carbon products is a promising way for tackling carbon emissions and restoring renewable electricity, which still lacks of efficient electrocatalysts. Herein, Cu2O nanoparticles with rough surface and abundant oxygen vacancies were facilely prepared by using an ionic liquid, [Omim]Cl (1-octyl-3-methylimidazolium chloride), as a bifunctional structure-directing agent, where the [Omim]+ played a role of surfactant to adjust the morphology of Cu2O and the Cl− facilitated the formation of oxygen vacancies by coordination with Cu+. The obtained Cu2O nanoparticles were further dispersed on the home-made graphite nanosheets to fabricate a composite catalyst, which showed an excellent catalytic performance with high faradaic efficiency of C2 (78.5 ± 2%) and commercial-level current density (123.1 mA cm−2) at − 1.1 V vs. RHE for 100 h in a flow cell. In situ surface-enhanced Raman spectroscopy and density functional theory calculations proved the special structure of Cu2O strengthened the adsorption of intermediates (CO2•−, CO*) and the following C–C coupling reaction, thus remarkably promoting the formation of C2 products. This work affords a novel strategy to synthesize metal oxide with controllable morphology and defects for electrochemical applications.