Conformal iCVD‐Modified Electrodes for Enhanced Mass Transfer in High‐Rate CO₂ Electroreduction

Abstract Gas diffusion electrodes hold significant potential in the field of CO 2 reduction, yet facing a major challenge of flooding within the catalyst layer. Common modification methods, such as coating with hydrophobic organics or incorporating them to catalyst inks, tend to seal gas transport pores or impact electrical conductivity, limiting the enhancement of current density during electrocatalytic CO 2 reduction reaction. This paper describes the design and realization of a conformal hydrophobic modification, which is enabled by initiated chemical vapor deposition (iCVD) that conformally deposits a controllable thickness of hydrophobic poly(1H, 1H, 2H, 2H‐perfluorodecyl acrylate, PFDA) (PPFDA) inside aggregated Ag nanoparticles with interstitial porosity, loaded on carbon paper. Characterization and electrocatalytic experiments reveal that the hydrophobic modification of iCVD not only prevents the sealing of gas‐transporting pores but also maintains electrode conductivity. This improvement facilitates enhanced mass transfer of gaseous CO 2 during electrochemical CO 2 reduction reaction, leading to an increase in current density. The iCVD conformally modified electrodes exhibited excellent electrocatalytic performance in both a flow cell and a membrane electrode assembly (MEA) electrolyzers. A notable CO Faradaic efficiency of 93.5% is achieved at a current density of 300 mA cm −2 in a 4 cm 2 MEA electrolyzer, accompanied by an exceptional stability improvement.