Electroreduction of CO to 2.8 A cm⁻ 2 C 2+ Products: Maximizing Efficiency with Minimalist Electrode Design Featuring a Mesopore-Rich Hydrophobic Copper Catalyst Layer.

This work shows how hydrophobicity and porosity can be incorporated into copper catalyst layers (CLs) for the efficient electroreduction of CO (CORR) in a flow cell. Oxide-derived (OD) Cu catalysts are synthesized using K + and Cs + as templates, termed respectively as OD-Cu-K and OD-Cu-Cs. CLs, assembled from OD-Cu-K and OD-Cu-Cs, exhibit enhanced CORR performance compared to "unmodified" OD-Cu CL. OD-Cu-Cs can notably reduce CO to C 2+ products with Faradaic efficiencies (FE) as high as 96% (or 4% FE H 2 ). During CO electrolysis at -3000 mA cm -2 (-0.73 V vs reversible hydrogen electrode), C 2+ products and the alcohols are formed with respective current densities of -2804 and -1205 mA cm - 2 . The mesopores in the OD-Cu-Cs CL act as barriers against electrolyte flooding. Contact angle measurements confirm the CL's hydrophobicity ranking: OD-Cu-Cs > OD-Cu-K > OD-Cu. The enhanced hydrophobicity of a catalyst is proposed to allow more triple-phase (CO-electrolyte-catalyst) interfaces to be available for CORR. This study shows how the pore size-hydrophobicity relationship can be harvested to guide the design of a less-is-more Cu electrode, which can attain high CORR current density and selectivity, without the additional use of hydrophobic polytetrafluoroethylene particles or dopants, such as Ag.