Ternary Fe/N/C catalysts are regarded as the most promising candidate of low-cost alternative to Pt for catalyzing the oxygen reduction reaction (ORR). High-temperature pyrolysis of N-containing carbon precursors in the presence of Fe salts has been a common and efficient route to prepare the Fe/N/C catalysts. However, simple pyrolysis usually leads to large weight loss of N-containing precursor, which not only increases the overall cost of the catalysts, but also results in catalysts having low density of active sites. We show herein that this problem can be effectively overcome by dispersing a highly hydrosoluble polymer precursor, namely, the polyvinylpyrrolidone (PVP), in the NaCl crystallites. The use of the hydrosoluble polymer precursor enables efficient dispersing and confining of precursor in NaCl crystallites in a simple solvent evaporation process. The subsequent pyrolysis process not only shows little weight loss, but produces a mesoporous Fe/N/C ORR catalyst with remarkably higher specific surface area (414.5 m² g ^-1 ) and ORR activity (half-wave potentials, E_1/2=0.793 V and 0.878 V vs. RHE respectively in acidic and alkaline media) than the material prepared without using the NaCl confinement (72.9 m² g ^-1 , E_1/2=0. 634 V and 0.785 V respectively in acidic and alkaline media), as well as superior stability under the ORR condition.

        https://pubs.rsc.org/en/content/getauthorversionpdf/c6ta05075a