Enhanced Electrocatalytic CO2 Reduction to C2+ Products by Adjusting the Local Reaction Environment with Polymer Binders

The activity and selectivity of the electrochemical CO2 reduction reaction (CO2RR) are often hindered by the limited access of CO2 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 CO2 relative to H2O at the vicinity of the catalyst and thus the performance of CO2RR. 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 approximate to 1.2 nm, these binders strongly affect the activity and selectivity toward multi-carbon (C2+) products. The FEP coated catalyst exhibits a C2+ partial current density of over 600 mA cm(-2) with approximate to 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 H2O and enhances that of the reactant (i.e., CO2) 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.