Differential Pressure Across a Gas Diffusion Electrode Controls Efficiency of Liquid-Fed Electrolyzers for CO<sub>2</sub> Electroreduction at Elevated Temperatures
Alana Rossen, Nick Daems, Daniel Choukroun, Tom Breugelmans
Abstract
Commercialization of emerging power-to-X conversion technologies requires efficient integration and recovery of heat and waste within existing chemical plants. The electrochemical reduction of CO 2 fits such a scope, yet current research largely neglects the prospect of elevated temperature operation, which is likely to occur due to Joule heating and cooling constraints. Here, we set out to investigate the performance of liquid-fed CO 2 electrolyzers at temperatures of up to 85 °C─a threshold that exacerbates commonly met stability issues and leads to electrolyzer failure. To prevent the latter, our study first explores the interrelationships between elevated temperature operation, evaporation, gas solubility, electro-wetting, and how they affect performance. At 25 °C, unity selectivity to formate is demonstrated over the course of 24 h. However, at 85 °C, we show that fine optimization of differential pressure (28–40 mbar) has to be carried out to stabilize performance. Ultimately, a faradaic efficiency of 64% could be maintained after 24 h of electrolysis at −100 mA cm –2 ─a 68% improvement relative to the nonoptimized system. The substrate-dependent rate of performance decline at 85 °C, which is not distinguishable at ambient temperatures, underscores the necessity for a tailored system and differential pressure control for CO 2 electrolysis at elevated temperatures.