Minimization of Pt-electrocatalyst deactivation in CO₂ reduction using a polymer electrolyte cell

Diluted CO₂ feeding was recently reported to efficiently generate CH₄ at the theoretical Pt electrode potential, however, the reaction was easily deactivated. To solve this problem, we investigated the reaction/deactivation mechanism to produce CH₄ from CO₂ electroreduction. Using a polymer electrolyte single cell containing a Pt/C catalyst, CO₂ was reduced to CH₄ without overpotential by simply controlling the CO₂ feed concentration. The CH₄ synthesis proceeded if the Pt–CO/Pt–H ratio formed on the Pt-catalyst surface was 1 : 11 or higher. The deactivation of the CH₄ generating reaction also depends on the Pt–CO/Pt–H ratio (the ratio does not satisfy 1 : 11 or higher). The optimum Pt–CO/Pt–H ratio to produce CH₄ was 1 : 18. Furthermore, we achieved 86% recovery of CH₄ activity by sweeping the deactivated Pt surface on the cathode up to 0.3 V where the CO₂/Pt–CO redox reaction occurred simultaneously. As a result, an efficient less energy-intensive reactivation reaction that we defined as a poisoning-elimination method was established. Overall, this work demonstrated that the application of a polymer electrolyte cell together with a low concentration of CO₂ is effective to minimize Pt-electrocatalyst deactivation.