Reduction of Break-In Duration for Polymer Electrolyte Fuel Cells through an Approach To Accelerate the Removal of Impurities in the Electrode

High productivity of fuel cell stacks is essential for the widespread adoption of polymer electrolyte fuel cells (PEFCs). The conditioning process (also called break-in) of a PEFC can take several hours, potentially becoming a bottleneck in mass production. In this study, the cause of the long break-in duration in the production of Toyota Mirai fuel cell stacks was identified through electrochemical measurements and sample analyses, and effective protocols were developed to reduce the duration. The primary cause of the extended duration was found to be organic contamination during the cell production process. Synchronizing the timing of electricity generation with the lowering of the cathode potential was found to be effective in promptly washing away contaminants from the Pt surface of the cathode catalyst using produced water. This concept was applied to the break-in process of the second-generation Mirai stacks, enabling a 70% reduction in the duration compared with the protocol for the first-generation Mirai stacks.