Ag-deposited Ti gas diffusion electrode in proton exchange membrane CO2 electrolyzer for CO production

Abstract

Electrochemical CO2-to-CO conversion is techno-economically effective for utilizing CO2. Although numerous studies are available on CO2 conversion catalysts, many of them are limited to a half-cell or conventional H-type apparatus in aqueous mediums, providing insufficient CO2 feeding. In this study, as a part of pioneering works on gas-feeding reactors, a gas diffusion electrode consisting of a Ti substrate with affixed Ag electrocatalysts was suggested; this enables the mass conversion of CO2 via direct feeding of CO2. Herein, Ag catalysts were electrodeposited on a Ti gas diffusion layer for a proton exchange membrane-based CO2 electrolyzer. Pre-treatment of the Ti crucially influenced the deposition profile, adhesiveness, morphology, and electrochemical surface area of the Ag deposit, which influence the CO2/CO conversion efficiency of the catalyst. Pre-treatment with HCl-H2SO4 conferred the highest roughness and hydrophilicity to the Ti substrate, leading to the highest surface area of the Ag catalyst and a consequent substantial increase in the CO2/CO conversion efficiency (45% at Vcell=−2.2V), which is a 5.7-fold increase when compared with the un-treated counterpart. The fabrication of Ag/Ti gas diffusion electrode via simple Ag electrodeposition and optimized Ti pre-treatments reported herein provides a guide for manufacturing proton exchange membrane-based CO2 electrolyzers.