Progress in ionomer-based microenvironment engineering of gas diffusion electrodes for electrochemical CO2 reduction

Abstract

The electrochemical CO2 reduction reaction (CO2RR) has emerged as a promising pathway toward net-zero emissions and carbon neutrality. For efficient CO2RR, optimizing the microenvironment of catalysts in the gas diffusion electrode (GDE) system is essential. Ionomer, composed of hydrophobic polymer chains and hydrophilic ionic groups, can be utilized to optimize the CO2 mass transfer and surface properties of catalyst layers in GDE. This review highlights the effect of ionomers on microenvironment modulation and their role in enhancing the CO2RR performance. The chemical structure of the ionomer can control its intrinsic properties, including the crystallinity of the ionomer matrix, charge or ion transport, and water uptake behavior. These characteristics of the ionomers can modulate the microenvironment of CO2RR catalysts and influence catalytic reaction efficiency. Therefore, ionomer can control CO2 availability, local pH, and cation effects, as well as stabilize the intermediate adsorption. By addressing the stability challenges of ionomer materials during electrolysis, this review further offers perspectives on the design strategies of ionomer-enhanced catalysts for efficient CO2RR.