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 degrees 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 degrees 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 degrees 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 degrees C, which helps to suppress the increasing rate of hydrogen evolution and with that a mechanical degradation of the GDE.