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Microstructure Engineering of Fe/Fe3C‑Decorated Metal–Nitrogen–Carbon Mesoporous Nanospheres via a Self-Template Method for Enhancing Oxygen Reduction Activity

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journal contribution
posted on 11.06.2020, 19:34 by Wanxin She, Qianru Xie, Yaohui Huang, Chuyi Xie, Xiangyu Zhang, Mingchen Sun, Feng Wang, Junwu Xiao
We report a self-template and facile pyrolysis method to synthesize Fe/Fe3C-decorated metal–nitrogen–carbon mesoporous nanospheres, of which preserved plum-like and hollow structures can be simply engineered via controlling the thickness of the outermost polydopamine layer in the precursors. The preserved plum-like structure is demonstrated to show a large electrochemically active surface area and facilitate fast charge transfer, in comparison with the hollow one. The catalytic activities of metal–nitrogen–carbon and nitrogen-doped carbon active sites in the outer carbon layer toward oxygen reduction are improved under the activation of the encased Fe species. Hence, preserved plum-like structures exhibit excellent catalytic kinetics toward the oxygen reduction reaction in alkaline media. The mass activity of 21.0 mA mgcatalyst–1 at 0.9 V vs RHE is achieved and the half-wave potential is 50 mV more positive than that of the Pt/C catalyst with the same mass loading. Moreover, the outer carbon layer endows the tolerance of strong acidic and alkaline environments, resulting in good durability. Our study proposes a simple strategy for the rational design of novel transition metal carbide-based catalysts, making it a promising candidate for replacing platinum-group metal catalysts in low-temperature fuel cells.