Flooding\nControl by Electrochemically Reduced Graphene\nOxide Additives in Silver Catalyst Layers for CO<sub>2</sub> Electrolysis

Electrolyte flooding\nin porous catalyst layers on gas diffusion\nelectrodes (GDE) limits the stability and high-current performance\nof CO<sub>2</sub> and CO electrolyzers. Here, we demonstrate the in\nsitu electroreduction of graphene oxide (GO) to reduced graphene oxide\n(r-GO) within a silver catalyst layer on a carbon GDE. The r-GO introduces\nhydrophobicity regions in the catalyst layer that help mitigate electrolyte\nflooding during high current density CO<sub>2</sub> electrolysis to\nCO. The flooding-resistant r-GO/Ag-coated GDE achieves a sustained\nFaradaic efficiency of CO at 94% for more than 8 h, compared to a\nrapid drop from 95% to 66% in an Ag-coated GDE without r-GO at 100\nmA·cm<sup>–2</sup>. We found that GO enhances the electrochemically\nactive surface area of the catalyst layer during CO<sub>2</sub> electrolysis\ntests because the incorporation of GO increases the roughness of the\ncatalyst layer. The in situ method of electrochemically reducing GO\nto r-GO provides a low-cost, practical approach that can be applied\nduring standard spray-deposition procedures to develop flooding-resistant\nGDEs.