One-pot synthesized covalent porphyrin polymer-derived core-shell Fe3C@carbon for efficient oxygen electroreduction

The mass production of non-precious metal catalysts (NPMCs) with high catalytic performance for oxygen reduction reaction (ORR) is highly desirable for promoting the commercialization of proton membrane fuel cells. In this work, one-pot synthesized covalent porphyrin polymers (CPP) incorporated with iron chlorides (Fe-CPP) were converted into N-doped porous Fe3C@carbons (Fe3C@C) at a scale of over 10 g in one run by the template-free pyrolysis. The derived Fe3C nanocrystals with 10-50 nm particle size were encapsulated in the special N-doped carbon shells. The Fe3C@C obtained at the carbonization temperature of 900 °C had high graphitization degree and hierarchical pore structures with an appropriate surface area of 441.6 m2 g−1. The unique local structures and highly active sites for ORR including Fe3C activated carbon shells as well as Fe-Nx and the pyridinic and graphitic N sites contributed to the efficient catalytic performance of this core-shell Fe3C@C. It exhibited the ORR half-wave potential of 0.80 V in 0.1 M KOH and 0.68 V in 0.1 M HClO4, close to commercial 20 wt % Pt/C but with superior stability in both media. The template-free thermal conversion of easily-prepared Fe-CPP provided an industrially feasible synthesis for cost-effective Fe3C@C NPMCs with efficient electroreduction activity for ORR.

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