Improving the operational stability of electrochemical CO2 reduction reaction via salt precipitation understanding and management

Abstract

The practical application of electrochemical carbon dioxide reduction reaction (CO₂RR) technology remains hindered by poor stability, primarily owing to bicarbonate salt formation at the cathode, which blocks reactant CO₂ mass flow. Here, using operando characterization tools, we tracked the salt formation process and quantified salt precipitation under varying device operational conditions, elucidating a potential mechanism and optimizing anolyte conditions for long-term (>1,000 h) operation CO₂RR to CO under >100 mA cm^–2. Liquid droplets carrying cations and (bi)carbonate ions were observed to migrate from the catalyst/membrane interface towards the backside of the gas diffusion electrode, driven by interfacial gas evolution and CO₂ flow. These droplets eventually dried, forming bicarbonate salt precipitates that blocked the gas flow channels. On the basis of this observation, we applied a hydrophobic parylene coating to the cathode gas flow channel surface, facilitating the removal of the droplets and extending stability from ~100 h to over 500 h under 200 mA cm^–2.