Metal-free, NH3-activated N-doped mesoporous nanocarbon electrocatalysts for the oxygen reduction reaction

Abstract

Lowering the cost of electrocatalysts for the oxygen reduction reaction (ORR) is indispensable for the wider commercialization of fuel cells. Therefore, the development of non-Pt, especially metal-free, carbon-based electrocatalysts, has been encouraged as an alternative to Pt. Here, we report active N-doped nanocarbon electrocatalysts in ORR activated by thermal treatment of pristine carbon precursors with highly aligned mesopore channels under an NH3 atmosphere. This NH3-activation process adopts N-containing carbon sites, leading to enhanced ORR performance in an alkaline electrolyte with negligible formation of peroxide species. The stability of the activated carbon electrocatalysts was confirmed by performing 40,000 rounds of potential cycles in the accelerated stress test (AST). The variations in the voltammograms during AST were analyzed using X-ray photoelectron spectroscopy. The correlation between electrochemical behavior and the N 1 s spectrum corroborates the contribution of N-related sites toward voltammetric responses in ORR.