Reorganization of Interfacial Water By an Amphiphilic Cationic Surfactant Promotes CO2 Reduction

Abstract

The presence of cetyltrimethylammonium bromide (CTAB) near the surface of a Cu electrode promotes the electrochemical reduction of CO2-to-fuels. The presence of CTAB increases the CO2 reduction rate by as much as 10x and decreased the HER rate by 4x, leading to ~75% selectivity towards the reduction of CO2. We utilized Surface Enhanced Infrared Absorption Spectroscopy (SEIRAS) to probe the dynamics of CTAB adsorption on the structure of interfacial water and CO2 reduction intermediates. HER suppression was found to arise from the displacement of interfacial water molecules from the presence of CTAB in the double layer. The enhanced CO2 reduction rate can be correlated to an increased population of atop bound CO and the emergence of a low frequency atop CO band. These results unravel the role of additives in improving CO2-to-fuels electrocatalysis and establishing this as a powerful methodology for directing product selectivity.