Ordered Mesoporous Porphyrinic Carbons for Oxygen Reduction Reaction: Pt-like Activity in Acidic Media and Active Site

The high cost of polymer electrolyte fuel cell (PEFC) systems, predominantly dictated by the platinum-based cathode catalysts for the oxygen reduction reaction (ORR), has critically impeded the widespread application of PEFCs. Therefore, the quest for low-cost yet high-performance non-precious metal catalysts has been of prime importance in recent years. We present a new class of self-supported, transition metal-doped ordered mesoporous porphyrinic carbon (M-OMPC; M=transition metal) catalysts, which were prepared by nanocasting mesoporous silica templates with metalloporphyrin precursors [1]. The preparation of M-OMPC catalysts is simple, tunable, scalable, and highly reproducible. Among the M-OMPC catalysts, FeCo-OMPC exhibits a very high ORR activity in an acidic medium, which is one of the best performances among the non-precious M/N/C catalysts, and outperformed the carbon-supported commercial Pt/C catalyst. Furthermore, the FeCo-OMPC showed superior long-term durability in ORR, compared to Pt/C; after cycling 10,000 times under O₂ bubbling, the FeCo-OMPC exhibited 6-fold higher ORR activity than the Pt/C. The weakening of the interaction between oxygen atom and the FeCo-OMPC compared to Pt/C as well as high surface area of the former could be responsible for its significantly high ORR activity. We also systematically investigated the potential active sites for the ORR in the FeCo-OMPC catalysts, and could correlate the local coordination structure around metal centers and corresponding ORR activities [2]. The M-OMPC catalysts could suggest a new concept for future design of non-precious metal-based high-performing ORR catalysts.

[1] J. Y. Cheon, T. Kim, Y. Choi, H. Y. Jeong, M. G. Kim, Y. J. Sa, J. Kim, Z. Lee, T.-H. Yang, K. Kwon, O. Terasaki, G.-G. Park, R. R. Adzic, S. H. Joo, Scientific Reports 3, 2715 (2013).

[2] J. Y. Cheon, M. G. Kim, G.-G. Park, S. H. Joo, manuscript in preparation.