Potential Cycling of Silver Cathodes in an Alkaline CO₂Flow Electrolyzer for Accelerated Stress Testing and Carbonate Inhibition

The electrochemical reduction of CO2 (CO2RR) holds promise for the reduction of environmentally taxing CO2 emissions, for the carbon-neutral production of valuable fuels and chemicals, and for storage of excess renewable energy from intermittent sources such as wind and solar in chemical products. Durability of cathodes used in high-throughput CO2RR systems is of paramount importance for the commercial readiness of the CO2RR technology. In this study, we investigate the durability of silver-coated gas diffusion electrode cathodes under potential cycling conditions to simulate the impact of repeated cycles of startup and shutdown as might be experienced in connection with a variable renewable power source. We determine that cycling can impact the cathode via two distinct degradation mechanisms: (1) carbonate formation at negative potentials and (2) catalyst layer restructuring and loss in the relatively positive “oxide formation” potential range. We also explore tailored potential cycling as a mechanism for inhibiting carbonate formation by interrupting the high concentration of OH– at the catalyst layer. The findings from this work lend insight into the types of variable potential operating conditions under which CO2RR systems can deliver continuous, robust performance.