Interconnected Fe, S, N-Codoped Hollow and Porous Carbon Nanorods As Efficient Electrocatalysts for the Oxygen Reduction Reaction

As promising precious metal-free oxygen reduction reaction (ORR) electrocatalysts, Fe-N-C catalysts still face a great challenge to meet the requirement of practical applications. In this study, Fe, S, N-codoped hollow and porous carbon nanorods (Fe-S-N HPCNRs) were designed with the aim of improving the performance of Fe-N-C catalysts from the perspective of composition and structure. They were successfully prepared using cysteine, Fe salt, and polydopamine-encapsulated ZnO nanorods (ZnO NRs@PDA) as precursors by a pyrolysis-acid etching strategy. The hollow and porous structure and composition of Fe, S, N, and C were verified by transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy tests. At the optimum ratio of ZnO NRs@PDA/cysteine and pyrolysis temperature, the Fe-S-N HPCNRs display higher ORR activities than the control samples which are lack of one of the precursors. Electrochemical tests show that the ORR follows a 4e pathway with the Fe-S-N HPCNRs. In addition, the long-term stability and methanol tolerance of Fe-S-N HPCNRs are good and superior to those of 20 wt % Pt/C.