Power source research at USC: Development of advanced electrocatalysts for polymer electrolyte membrane fuel cells

This paper provides an overview on the development of advanced fuel cell cathode catalysts at University of South Carolina (USC) with the emphasis on the stability of non-precious metal and Pt alloy catalysts. Nitrogen-modified carbon composite (NMCC) catalysts were developed for the oxygen reduction reaction (ORR) through the pyrolysis of cobalt (iron)–nitrogen chelate followed by the treatment combination of pyrolysis, acid leaching, and re-pyrolysis. A promising stability was observed for 1050 h fuel cell operation under current density of 200 mA cm−2 as evidenced by a potential decay rate as low as 40 μV h−1. The performance degradation mechanism of the NMCC-based fuel cell is discussed. Pt and PtPd hybrid catalysts are developed that use a NMCC, which is itself active for the ORR, instead of a conventional carbon black support. The stability test at 1 A cm−2 indicated that the Pt/NMCC hybrid catalyst (new Pt–Co/C) is more stable than the conventional Pt–Co/C without the Co leaching out. The PEM fuel cell accelerated stress test (AST) for supports and catalysts demonstrated that their stability changes in the order: Pt3Pd1/NMCC hybrid catalyst > Pt/NMCC hybrid catalyst > conventional Pt/C catalyst. Moreover, the hybrid catalysts exhibit higher mass activity than the Pt/C catalysts.