A novel type of Nitrogen-Boron-Carbon ternary nanosheets (NBCs) was prepared directly from graphitic-phase carbon nitride (g-C3N4) and achieved high yields. In these NBCs, the molar content of nitrogen and boron can exceed that of carbon, at the same time with good electronic conductivity. It was observed that there is a coexistence tendency for B/N two elements which was able to maintain the aromaticity of micro-regions. The Morphology analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectrum results point to a two-dimensional conjugated dominated structure. In addition, NBCs exhibited superior electrochemical performance for ORR with much better methanol tolerance and catalytic stability than commercial Pt/C catalyst. NBCs also showed excellent catalytic activity for HER in aqueous solutions over a wide range of pH values, including acidic, neutral and alkaline conditions. These ternary nanosheets of such high N and B content has not been previously reported and potentially open up a broad research and application prospects. (C) 2018 Elsevier B.V. All rights reserved.