Activating Copper for Electrocatalytic CO2 Reduction to Formate via Molecular Interactions

Cu is a well-known electrocatalyst for reducing CO2 to various products. However, unmodified Cu exhibits poor selectivity and activity for formate production. Our in situ Raman spectroscopy study detects HCOO* intermediates on the unmodified Cu surface under CO2 electroreduction reaction conditions and confirms their reductive desorption being the rate-limiting step of producing formate. We further show that cetyltrimethylammonium bromide (CTAB) can dramatically improve the catalysis via competitive adsorption to facilitate HCOO* desorption. The Cu-CTAB interaction leads to a faradic efficiency of 82% and a 56-fold increase in partial current density for CO2 reduction to formate at -0.5 V vs the reversible hydrogen electrode in a near-neutral aqueous solution, which is the best performance to date for unmodified Cu under ambient conditions.