In-situ self-templated preparation of porous core–shell Fe1−xS@N, S co-doped carbon architecture for highly efficient oxygen reduction reaction

Abstract Transition metal compound (TMC)/carbon hybrids, as prospering electrocatalyst, have attracted great attention in the field of oxygen reduction reaction (ORR). Their morphology, structure and composition often play a crucial role in determining the ORR performance. In this work, we for the first time report the successful fabrication of porous core–shell Fe1−xS@N, S co-doped carbon (Fe1−xS@NSC-t, t represents etching time) by a novel in-situ self-template induced strategy using Fe3O4 nanospheres and pyrrole as sacrificial self-template. The post-polymerization of pyrrole can be accomplished by the Fe3+ released through the etching of Fe3O4 by HCl acid. Thus, the etching time has a significant effect on the morphology, structure, composition and ORR performance of Fe1−xS@NSC-t. Based on the characterizations, we find Fe1−xS@NSC-24 can realize effective and balanced combination of Fe1−xS and NSC, possessing porous core–shell architecture, optimized structure defect, specific surface area and doped heteroatoms configurations (especially for pyridinic N, graphitic N and Fe-N structure). These features thus lead to outstanding catalytic activity and cycling stability towards ORR. Our work provides a good guidance on the design of TMC/carbon-based electrodes with unique stable morphology and optimized structure and composition.