Tuning Selectivity of Acidic Carbon Dioxide Electrolysis via Surface Modification

Electrocatalytic CO 2 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 CO 2 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.