Tuning Selectivity of Acidic Carbon Dioxide Electrolysis via Surface Modification

Electrocatalytic CO2 reduction to energy-dense organic compounds useful for industry is an interesting strategy for organic synthesis using non-fossil carbon feedstocks and for storing energy from intermittent sources in the form of chemical energy. Electrolysis under acidic conditions has been recently studied as a promising way to avoid carbon loss due to the inevitable carbonate formation using traditional neutral or alkaline electrolytes. Here we report one of the very first examples showing that a molecular modification of the surface of copper nanoparticles allows tuning the selectivity of the reaction toward favoring C-2 products, ethylene and ethanol, at industrially relevant current densities at acidic pH (<1). This is achieved thanks to the electrodeposition of an imidazolium-based layer on the nanoparticles and performing electrolysis using a gas-fed flow cell with an acidic catholyte. Moreover, acidic CO2 electroconversion in the absence of alkali cations is reported for the first time, providing new perspectives for addressing the problems associated with the utilization of catholytes containing alkali cations.