Screening of Binder Materials for Ag-Based Gas Diffusion Electrodes for CO₂ Conversion to CO

Abstract

Electrochemical CO₂ reduction (CO₂R) to chemicals and fuels has made tremendous progress since the introduction of gas diffusion electrodes (GDEs) to overcome mass-transfer limitations and enable industrial-scale current densities. The advancement in the field, however, has come with new challenges that are related to the stability and degradation of the GDE due to flooding issues, which currently hinder the scale-up. Here, we investigated the effect of six different binding materials (Nafion, polytetrafluoroethylene, Fumion, Pention, poly(vinyl alcohol), and polypyrrole) on the stability and performance of Ag-based GDEs for CO₂R to CO in alkaline media. All binders show a decrease in the Faraday efficiency (FE) of CO and increase in hydrogen evolution reaction over time. The most hydrophilic GDE based on polypyrrole can uphold a higher FE of CO for longer times, which is contrary to a common belief that low wettability is required for long-term stability. By using a range of tools (SEM-EDX, SEM-FIB, X-ray diffraction, and contact angle measurements) for the postelectrolysis characterization of the GDEs, we show that the performance loss is related to flooding, bi(carbonate) precipitation, and catalyst agglomeration. These results contribute to a better understanding of the stability issues in GDE-based CO₂ electrolyzers.