Cu-Ag gas diffusion electrodes for electrochemical CO2 reduction to multi-carbon products

Electrochemical CO₂ reduction can produce low-carbon fuels using sustainable electricity, contributing to climate-change mitigation. In this work, we modify the surface of CuO x gas-diffusion electrodes (GDEs) with Ag using a simple spontaneous electrochemical deposition method. The prepared catalysts were tested in a three-chamber flow GDE reactor to evaluate their electrochemical performance and product distribution. Several products were obtained, including carbon monoxide, ethylene, ethanol, 1-propanol, and hydrogen. The addition of Ag on the Cu-GDE surface enhances the formation of C₂⁺ products and suppresses hydrogen evolution. A CuO x GDE with 8-min Ag deposition achieves a C₂⁺ faradaic efficiency of over 60% with a current density of 130 mA cm⁻² at −1.15 V vs RHE. Pseudo-in-situ X-ray photoelectron and Raman analyses indicate that copper oxide reduction is slower in CuO x -Ag GDEs than in pristine CuO x . Density functional theory calculations show that Ag promotes Cu migration toward the electrode surface, enabling stronger CO adsorption and facilitating further reduction to multi carbon C₂⁺products. The reduction in CO faradaic efficiency from 28% to 15% correlates with the increase in C₂⁺ efficiency from 35% to 65% for the CuOx-Ag (8-min) sample compared with pristine CuO x , supporting the theoretical findings. This study demonstrates the enhanced C₂⁺ selectivity of CuO x -Ag catalysts and provides mechanistic insight through pseudo-in-situ spectroscopy, offering guidance for the development of efficient systems for electrochemical CO₂ conversion to C₂⁺ compounds.