Membrane-controlled CO2 electrocatalysts with switchable C2 product selectivity and high faradaic efficiency for ethanol

Abstract

Bimetallic Cu materials are promising CO₂ reduction electrocatalysts for the formation of valuable multicarbon products. We describe membrane-modified Ag–Cu electrocatalysts that convert CO₂ to C2 products with high selectivity. While traditional Ag–Cu catalysts generate ethylene (C₂H₄) as the main product, we demonstrate that product selectivity can be switched to ethanol (C₂H₅OH) by introducing a proton-permeable fluoropolymer. By optimizing the catalyst composition, voltage, and membrane thickness and identity, we develop a catalyst that generates C₂H₅OH with up to 72% faradaic efficiency, making it the most selective Ag–Cu catalyst for C₂H₅OH reported. Lastly, we discuss a detailed chemical mechanism that explains how the hydrophobicity of the membrane overlayer enables catalysts with switchable C2 product selectivity.