Synthesis of three-dimensional flowerlike nitrogen-doped carbons by a copyrolysis route and the effect of nitrogen species on the electrocatalytic activity in oxygen reduction reaction

Three-dimensional flowerlike nitrogen-doped carbons (NCs) have been prepared by copyrolysis of solid ferrocene and melamine at 500–700 °C. X-ray photoelectron spectroscopy N1s spectra show three kinds of C–N bonding patterns: pyridinic-, pyrrolic-, and graphitic-type nitrogen species, and the atomic percentage of doping nitrogen can be adjusted between 0.67% and 4.62% by controlling reaction temperature. The electrocatalytic performance of as-prepared NCs for oxygen reduction reaction (ORR) is evaluated, and it is found that the NC-600 with the highest content of pyridinic-type nitrogen species outperforms other NC catalysts in ORR electrocatalytic activity in terms of half-wave potential, number of electrons transferred, and kinetic current density. It suggests that the pyridinic-type nitrogen species are active sites of NC catalysts and responsible for the enhanced ORR performance. Compared with the commercial Pt/C catalyst, the as-prepared NC catalysts exhibit a superior methanol tolerance for ORR in alkaline medium.