In the past few decades, polymer electrolyte membrane fuel cells (PEMFCs), as a kind of clean, efficient energy sources, which is considered to be the most promising solution to solve the increasingly serious energy crisis and reduce the environmental pollution, have experienced continuously increasing attention¹. Oxygen reduction reaction (ORR) in fuel cells plays a decisive role in determination of performance, and electrocatalysts with high-performance ORR are essential for practical applications. However, the commercialization of PEMFCs has long been hindered by the utilized expensive Pt-based catalyst for cathodic ORR^{2 3}. To solve the bottleneck, non-platinum-group-metal electrocatalysts with low cost, high activity and durability have been intensively pursued as alternatives to Pt for the ORR⁴. Recent years witnessed the dramatic interest in using nitrogen/sulfer-doped porous carbon as one of the promising ORR catalysts. Herein, we present N/S-Me (Fe, Ni) doped porous carbon derived from a metal–organic frameworks MOF-67 (ZIF-N/S-Me-PC) as highly efficient ORR electrocatalysts. The catalytic ORR activities of ZIF-N/S-Me-PC are studied by linear sweep voltammetry (LSV), employing rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques to quantitatively obtain the ORR kinetic constants and the catalysts' possible reaction mechanisms. In comparison to the commercial Pt/C (20%), the electrocatalyst ZIF-N/S-Me-PC exhibits a pronounced positive shift in E_onset. In addition, it also demonstrates excellent long-term stability and durability during the 5000-cycle continuing-oxygen-supply (COS) accelerating durability tests (ADTs). Catalytic ORR activities were thoroughly examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), low-temperature N₂ adsorption and X-ray photoelectron spectroscopy (XPS).

References

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2 Q.W. Tang, L.M. Wang, M.J. Wu, N.N. Xu, L. Jiang, J.L. Qiao, J. Power Sources, 365, 348 (2017).

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4 M.J. Wu, Q.W. Tang, F. Dong, Z.Y. Bai, L. Zhang, J.L. Qiao, J. Catal, 352 , 208 (2017).