Si doped Fe-N/C catalyst for oxygen reduction reaction directed by ordered mesoporous silica nanospheres template strategy

Abstract

Template-assisted synthesis strategy is an effective approach to prepare high performance oxygen reduction catalyst. The Fe-N/C catalysts were prepared via high temperature pyrolysis of the composites containing Fe-loaded mesoporous silica nanospheres and polypyrrole wrapped on it (Fe/mSiO2@PPY). Fe loading ways combined with polymerization means of pyrrole greatly influence the structure and morphology of the final catalysts. By controlling the type of templates (mesoporous, microporous and nonporous templates) and synthesis conditions, Si doped Fe-N/C (Si-Fe-N/C) catalyst with hollow shell structures was obtained. The multiple heteroatom co-doping of Si, Fe and N in carbon framework are confirmed by EDS, XPS and Raman. The co-doping of Fe and N increases the oxygen reduction reaction (ORR) catalytic activities, while the doping of Si facilitates graphitization degree of carbon framework. The electrochemical performance of the Si-Fe-N/C catalyst was evaluated by the linear sweep voltammograms (LSV). It exhibits higher current density (5.4 mA cm−2) and more positive half-wave potential (0.83 V vs. RHE), which is comparable to commercial Pt/C catalyst. Stability tests show that the Si-Fe-N/C catalyst possesses excellent durability and more than 90% of its original activity can be retained after 50,000 s running at 0.68 V (vs. RHE).