Fe-N-C materials with atomically dispersed Fe–N4 sites could tolerate the poisoning of phosphate, and is regarded as the most promising alternative to costly Pt-based catalysts for the oxygen reduction in high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). However, they still face the critical issue of insufficient activity in phosphoric acid. Herein, we demonstrate a P-doping strategy to increase the activity of Fe-N-C catalyst via a feasible one-pot method. X-ray absorption spectroscopy and electron microscopy with atomic resolution indicated that the P atom is bonded with the N in Fe–N4 site through C atoms. The as prepared Fe-NCP catalyst shows a half-wave potential of 0.75 V (vs. reversible hydrogen electrode (RHE), 0.1 M H3PO4), which is 60 and 40 mV higher than that of Fe-NC and commercial Pt/C catalysts, respectively. More importantly, the Fe-NCP catalyst could deliver a peak power density of 357 mW·cm−2 in a high temperature fuel cell (160 °C), exceeding the non-noble-metal catalysts ever reported. The enhancement of activity is attributed to the increasing charge density and poisoning tolerance of Fe–N4 caused by neighboring P. This work not only promotes the practical application of Fe-N-C materials in HT-PEMFCs, but also provides a feasible P-doping method for regulating the structure of single atom site.
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Research Article
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Nano Research 2023, 16 (5): 6531-6536
Published: 23 December 2022
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