High-temperature polymer electrolyte fuel cells (HT-PEMFCs) show promise in heavy-duty vehicle application with the benefits in enhanced fuel impurities tolerance, easier heat rejection, and simpler water management. Typically, HT-PEMFCs operate under higher temperature (120-200 °C) with H3PO4 doped membrane and ionomer as the electrolyte, which creates a different environment for oxygen reduction reaction (ORR) as compared to that in low-temperature polymer electrolyte fuel cells (LT-PEMFCs). Regular catalyst screening in diluted acids at room temperature might not reflect ORR performance in HT-PEMFCs properly, as the catalyst may be exposed to concentrated H3PO4. Here, we report a simple modification to a typical rotating disk electrode setup to enable the analysis at elevated temperatures (up to 160 °C). ORR on Pt was studied in pure H3PO4 at temperatures between 80 °C and 160 °C and compared with similar tests in diluted HClO4 and H3PO4 solutions at room temperature. The electrochemical surface area, oxygen transport, and ORR activity are significantly suppressed in both diluted and pure H3PO4. Under high temperature, side reactions of H3PO4 reduction and H3PO3 oxidation are also observed. Understanding these changes provides new perspectives for HT-PEMFC’s ORR catalyst design and development.

Understanding oxygen reduction in high-temperature PEMFCs – a rotating disk electrode (RDE) study on Pt at elevated temperature (> 100 °C )

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