Iron oxide@graphitic carbon core-shell nanoparticles embedded in ordered mesoporous N-doped carbon matrix as an efficient cathode catalyst for PEMFC

Abstract

Developing electrocatalysts with high activity and long-term stability towards oxygen reduction reaction (ORR) in acidic media is still an important topic. However, most of the already reported non-precious-metal catalysts (NPMCs) for ORR exhibit excellent performance in basic media.In the present work, we report a newly designed FeOx@graphitic carbon core-shell structured nanoparticles implanted in N-doped carbon matrix, with ordered and mesoporous structure (FeOx@GC-NOMC), which i) exhibits a better electrocatalytic activity in acidic media, ii) follows a four-electron ORR process, and iii) shows superior stability and inertness to methanol when compared with commercial Pt/C (20 wt %). These features are mostly attributed to the following two points: i) the ordered mesoporous carbon matrix can not only be favorable for the rapid transfer and active sites exposure, but also limit the embedded nanoparticles size and avoid its agglomeration, and ii) the high content of “Fe-N” active sites, and the core-shell structure of embedded nanoparticles (FeOx@GC) can protect the active sites from the corrosion of harsh conditions and ensure the long-term durability.It is found that the as-prepared FeOx@GC-NOMC shows one of the best H2-O2 PEMFC single-cell performances, among all thetested and currently reported NPMCs, as well as a long-term durability. More precisely, at an open circuit potential of ca. 1 V, the peak power density reaches up to 350 W g−1 (1050 mW cm-2 based on active area). A slight current decay is observed after a chronoamperometric test of 120 h. The above features make FeOx@GC-NOMC a promising potential alternative to Pt/C for ORR electrocatalysis in practical fuel cell applications.