Construction of efficient electrodes for CO2RR through microenvironment regulation of hydrophobic ionomer

Abstract

CO₂ reduction reaction (CO₂RR) electrolyzers based on gas diffusion electrode (GDE) enable the direct mass transfer of CO₂ to the catalyst surface for participation in the reaction, thereby establishing an efficient three-phase reaction interface that significantly enhances current density. However, current hydrophobic modification methods face difficulties in achieving precise and substantial control over wettability, and the hydrophobic modifiers tend to significantly impair the conductivity of the electrode and ion transport capabilities. This study employs Nafion ionomers to hydrophobically modify the three-dimensional catalyst layer, revealing the bifunctionality of Nafion. The fluorinated backbone of Nafion ensures the hydrophobicity of the entire catalyst layer, while its sulfonic acid groups promote ion transport, without significantly affecting the conductivity of the electrode. Furthermore, by employing modifiers with distinct wettability characteristics, a highly efficient and large-scale manipulation of the hydrophilic/hydrophobic properties of the catalyst layer was successfully realized. The electrode, constructed with silver nanopowder as a representative catalyst and modified with the hydrophobic ionomer Nafion, exhibits a substantial enhancement in both catalytic activity and durability. The optimized electrode exhibited exceptional electrocatalytic performance in both flow cell and membrane electrode assembly (MEA) configurations. Notably, in the MEA, the electrode achieved a remarkable CO Faradaic efficiency (FE) of 93.3% at a total current density of 200 mA cm⁻², while maintaining stable operation for over 62 h.