Improving the Energy Efficiency of CO Electrolysis by Controlling Cu Domain Size in Gas Diffusion Electrodes

Abstract

Carbon monoxide electrolysis is a potential bridge between CO2-to-CO technologies and renewable C2+ platform chemicals, but CO reduction (COR) cathode performance must improve to advance these systems. A key challenge is designing COR catalyst layers on gas diffusion electrodes with adequate electron, ion, and gas transport for high current densities. Here we study the effects of Cu domain size and loading in catalyst layers composed of Cu nanoparticles (NPs) and PTFE gas-transporting domains. Using a special ink solvent that stably disperses PTFE, we optimize the PTFE content to create catalyst layers with networks of ∼5 μm wide Cu NP domains. Such layers provide favorable COR transport properties even at very high Cu loadings, which reduces the COR overpotential. In a 24 h electrolysis, an optimized Cu/PTFE electrode achieves a 73.5% single-pass conversion efficiency at 200 mA cm–2 and 2.13 V with 76% Faradaic efficiency for COR, including 18% for propanol.