(419f) PGM-Free and Iron-Free Catalysts for Oxygen Reduction in PEM Fuel Cells

High‐performance and inexpensive platinum‐group‐metal (PGM)‐free catalysts for the oxygen reduction reaction (ORR) in challenging acidic media are crucial for proton‐exchange‐membrane fuel cells (PEMFCs). Catalysts based on Fe and N codoped carbon (Fe–N–C) have demonstrated promising activity and stability. However, a serious concern is the Fenton reactions between Fe²⁺ and H₂O₂ generating active free radicals, which likely cause degradation of the catalysts, organic ionomers within electrodes, and polymer membranes used in PEMFCs. Alternatively, Co–N–C and Mn-N-C catalysts with mitigated Fenton reactions have been explored as promising replacements for Fe and PGM catalysts. In this presentation, we will introduce our recent progress of developing atomically dispersed and nitrogen coordinated Co and Mn single site catalysts for the ORR in PEMFC applications [1-3]. Catalyst synthesis, structure/morphology, activity and stability improvement, and reaction mechanisms will be discussed in detail. Combining experimental and theoretical understanding, the aim is to elucidate the structure–property correlations and provide guidance for rational design of advanced Co and Mn catalysts with a special emphasis on the fuel cell MEA performance and durability.

References:

(1) Li, J.; Chen, M.; Cullen, D. A.; Hwang, S.; Wang, M.; Li, B.; Liu, K.; Karakalos, S.; Lucero, M.; Zhang, H., Atomically dispersed manganese catalysts for oxygen reduction in proton-exchange membrane fuel cells. Nature Catalysis 2018, 1 (12), 935.

(2) Wang, X. X.; Prabhakaran, V.; He, Y.; Shao, Y.; Wu, G., Iron-Free Cathode Catalysts for Proton-Exchange-Membrane Fuel Cells: Cobalt Catalysts and the Peroxide Mitigation Approach. Advanced Materials, 2019, 31, 1805126.

(3) Wang, X. X.; Cullen, D. A.; Pan, Y. T.; Hwang, S.; Wang, M.; Feng, Z.; Wang, J.; Engelhard, M. H.; Zhang, H.; He, Y., Nitrogen‐Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells. Advanced Materials 2018, 30 (11), 1706758.

(4) He, Y.; Hwang, S.; Cullen, D. A.; Uddin, M. A.; Langhorst, L.; Li, B.; Karakalos, S.; Kropf, A. J.; Wegener, E. C.; Sokolowski, J., Highly active atomically dispersed CoN 4 fuel cell cathode catalysts derived from surfactant-assisted MOFs: carbon-shell confinement strategy. Energy & Environmental Science 2019, 12, 250-260.