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 (C₂₊) by electrochemical CO₂ reduction reaction (CO₂RR) is a promising technology that will contribute to the realization of a carbon‐neutral society. In particular, efficient CO₂RR to produce C₂₊ in acidic electrolytes is desirable because the conversion of CO₂ to inert (bi)carbonate can be suppressed under acidic conditions, thereby increasing the efficiency of substrate CO₂ utilization. Herein, since C₂₊ products are produced via the dimerization of carbon monoxide, an intermediate in CO₂RR, 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 C₂₊ production. The faradaic efficiency and partial current density for C₂₊ 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 C₂₊ 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 C₂₊ production.