Influence of Temperature on the Performance of Gas Diffusion Electrodes in the CO2 Reduction Reaction

A detailed investigation of the influence of operating temperature on the electrochemical reduction of CO2 to formate at tin oxide loaded gas diffusion electrodes (GDEs). Ambient pressure electrolysis is performed between 20 and 70 °C with a focus on maximizing current density and energy efficiency while maintaining an average formate faradaic efficiency of at least 80 %. The best performance is achieved at a temperature of 50 °C, which allows a current density of 1000 mA cm−2. Lower or higher temperatures both show an increased hydrogen evolution at said current density. Further investigation of CO2 transport limitation revealed a minimum at 50 °C, which is explained by the opposing influence of temperature on CO2 diffusion coefficients and solubility. This explanation is supported by an estimate of the current density at which hydrogen evolution starts to increase based on the flooded agglomerate model. Long‐term operation for 24 h also revealed an optimum temperature of 50 °C, which helps to suppress the increasing rate of hydrogen evolution and with that a mechanical degradation of the GDE. Beyond limits: Electrochemical CO2 reduction is a promising and intensively studied process to valorize this greenhouse gas. Even though gas diffusion electrodes are considered essential to overcome mass transport limitations, detailed investigations on the influence of temperature is lacking. In this Article, the temperature dependency of the electrodes activity and selectivity is described, and the observed results are correlated with a minimum in CO2 mass transport limitation.