Nitrogen−carbon materials base on pyrolytic graphene hydrogel for oxygen reduction

Abstract

HypothesisOxygen reduction reaction (ORR) has played a significant role in the utilization of energy nowadays. Nitrogen−doped carbon materials are seen as promising catalysts for ORR, so it is of great significance in studying the functions of different nitrogen moieties. ExperimentsThe graphene hydrogel−based nitrogen−arbon materials (GH N−C) were fabricated by first obtaining a gel through hydrothermal treatment using graphene oxide (GO) as precursor, and then calcined in an ammonia atmosphere at different temperatures to form N−doped graphitized materials with divers nitrogen configuration. FindingsGH N−C materials with tunable nitrogen configuration were synthesized by a two−step method base on graphene hydrogel. Benefiting from the 3D hydrogel structure, rich defects and optimized chemical properties, GH N−C−900 prepared by NH3 pyrolysis at 900 °C exhibits an excellent electrocatalytic performance toward ORR, with the onset potential of 0.947 ± 0.013 V versus RHE, half−wave potential of 0.830 ± 0.010 V versus RHE, electron transfer number of 3.61–3.99, along as methanol tolerance and superior long−term stability. Comprehensive studies have shown that there is a positive correlation between the total amount of pyrrolic−N and quaternary−N and the catalytic performance of ORR.