Carbon Monoxide Reduction Reaction to Produce Multicarbon Products in Acidic Electrolytes Using Gas Diffusion Electrode Loaded with Copper Nanoparticles

Abstract The synthesis of multi‐carbon products (C 2+ ) by electrochemical CO 2 reduction reaction (CO 2 RR) is a promising technology that will contribute to the realization of a carbon‐neutral society. In particular, efficient CO 2 RR to produce C 2+ in acidic electrolytes is desirable because the conversion of CO 2 to inert (bi)carbonate can be suppressed under acidic conditions, thereby increasing the efficiency of substrate CO 2 utilization. Herein, since C 2+ products are produced via the dimerization of carbon monoxide, an intermediate in CO 2 RR, the focus is on the carbon monoxide reduction reaction (CORR). A gas diffusion electrode loaded with copper nanoparticles is used in acidic electrolytes to investigate the conditions necessary for efficient C 2+ production. The faradaic efficiency and partial current density for C 2+ production attained 75% and 280 mA cm −2 in a pH 2.0 solution, and they reached up to 66% and 260 mA cm −2 even in a pH 1.0 solution. Numerical simulations showed that increasing the alkalinity of the electrode surface to greater than pH 7 by consuming protons is necessary to facilitate the production of C 2+ during the CORR. When the desired level of alkalinity is achieved, the concentration and type of alkali cations present at the electrode surface have an impact on the selectivity for C 2+ production.