Gas-assisted electrodeposition modulates the grain structure of Cu catalysts for selective conversion of CO2 to C2+ products

Electrochemical CO 2 reduction has attracted considerable research interest as a pathway to convert CO 2 into value-added multicarbon products. Cu is a key catalyst for multicarbon-product formation, and its selectivity is strongly affected by its microstructure. However, the effect of the gas environment during electrodeposition on Cu growth and subsequent CO 2 reduction performance remains poorly understood. Here, Cu catalysts were directly grown on a gas diffusion layer (GDL) in a flow-cell-based electrodeposition system while either CO 2 or Ar was supplied to the backside of the GDL, allowing the gaseous growth environment to be varied during deposition. The electrodes prepared under backside CO 2 supply exhibited finer surface features, and the representative Cu-gCO 2 −20 electrode showed a more highly subdivided crystallographic microstructure than the corresponding Ar-prepared electrode. These structural differences were associated with enhanced C 2+ selectivity during subsequent CO 2 reduction. Under representative operating conditions, the optimized electrode fabricated under CO 2 -supplied conditions achieved a C 2+ Faradaic efficiency of approximately 70% and an FE C2+ /FE C1 ratio of 5.5, compared with 2.7 for the corresponding Ar-prepared electrode. These findings highlight backside gas supply as an additional electrodeposition parameter for promoting the selective conversion and reuse of CO 2 into multicarbon products, including ethylene and ethanol.