Electroreduction of CO to 2.8 A cm⁻² C₂₊ Products: Maximizing Efficiency with Minimalist Electrode Design Featuring a Mesopore‐Rich Hydrophobic Copper Catalyst Layer

Abstract 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 C₂₊ products with Faradaic efficiencies (FE) as high as 96% (or 4% FE H₂). During CO electrolysis at −3000 mA cm⁻² (−0.73 V vs reversible hydrogen electrode), C₂₊ 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.