Proton-exchange membrane CO2 electrolyzer for CO production using Ag catalyst directly electrodeposited onto gas diffusion layer

Carbon monoxide is an important product of electrochemical CO2 reduction because its syngas mixture with H-2 can be used to synthesize hydrocarbons via the Fischer-Tropsch process. Herein, a hierarchical dendritic Ag catalyst for electrochemical CO2 reduction is prepared through pulse electrodeposition onto functionalized carbon paper. To gain the hydrophilicity required for contact with the deposition electrolyte, carbon paper is acid-treated to induce oxygen-containing functional groups on the surface. Among the acids tested, H2SO4 significantly enhances the morphological characteristics, such as population and size, of Ag clusters during pulse electrodeposition. This leads to lower charge transfer resistance and 1.6 times higher current density for CO production during CO2 electrolysis in a bath-type cell than those for Ag on pristine carbon paper. This superior activity is maintained in a membrane-electrode-assembly-type cell employing a proton-exchange membrane, which is desirable for mass production of CO. Thus, pulse electrodeposition of Ag onto H2SO4-treated carbon paper is a beneficial strategy to fabricate an electrode for a high-performance proton-exchange membrane CO2 electrolyzer.