Enhanced Electrocatalytic CO 2 Reduction to C 2+ Products by Adjusting the Local Reaction Environment with Polymer Binders

The activity and selectivity of the electrochemical CO 2 reduction reaction (CO 2 RR) are often hindered by the limited access of CO 2 to the catalyst surface and overtaken by the competing hydrogen evolution reaction. Herein, it is revealed that polymers used as catalyst binders can effectively modulate the accessibility of CO 2 relative to H 2 O at the vicinity of the catalyst and thus the performance of CO 2 RR. Three polymers with different hydrophilicities (i.e., polyacrylic acid (PAA), Nafion, and fluorinated ethylene propylene (FEP)) are selected as binders for Cu catalysts. At a thickness of only ≈1.2 nm, these binders strongly affect the activity and selectivity toward multi‐carbon (C 2+ ) products. The FEP coated catalyst exhibits a C 2+ partial current density of over 600 mA cm −2 with ≈77% faradaic efficiency at −0.76 V versus RHE. This high performance is attributed to the hydrophobic (aerophilic) properties of FEP, which reduces the local concentration of H 2 O and enhances that of the reactant (i.e., CO 2 ) and the reaction intermediates (i.e., CO). These findings suggest that tuning the hydrophobicity of electrocatalysts with polymer binders can be a promising way to regulate the performance of electrochemical reactions involving gas–solid–liquid interfaces.