Pyridinic N doped graphene: synthesis, electronic structure, and electrocatalytic property

Abstract

Different C–N bonding configurations in nitrogen (N) doped carbon materials have different electronic structures. Carbon materials doped with only one kind of C–N bonding configuration are an excellent platform for studying doping effects on the electronic structure and physical/chemical properties. Here we report synthesis of single layer graphene doped with pure pyridinic N by thermal chemical vapour deposition of hydrogen and ethylene on Cu foils in the presence of ammonia. By adjusting the flow rate of ammonia, the atomic ratio of N and C can be modulated from 0 to 16%. The domain like distribution of N incorporated in graphene was revealed by the imaging of Raman spectroscopy and time-of-flight secondary ion mass spectrometry. The ultraviolet photoemission spectroscopy investigation demonstrated that the pyridinic N efficiently changed the valence band structure of graphene, including the raising of density of π states near the Fermi level and the reduction of work function. Such pyridinic N doping in carbon materials was generally considered to be responsible for their oxygen reduction reaction (ORR) activity. The 2e reduction mechanism of ORR on our CN_xgraphene revealed by rotating disk electrode voltammetry indicated that the pyridinic N may not be an effective promoter for ORR activity of carbon materials as previously expected.