▎ 摘　　要

Preparing non-noble metal and metal-free electrocatalysts as the alternatives to noble metal-based materials, such as Pt/C, IrO2, is very necessary for energy conversion and storage. Carbon-based nanomaterials are promising candidates because of their low-cost, good electrical conductivity, and high surface area. Among the carbon nanomaterials, graphene and carbon nanotube are more excellent as the electrocatalysts for oxygen electrode reactions, especially heteroatoms doped graphene and carbon nanotube. Herein, we developed a bifunctional electrocatalyst composed of nitrogen, sulfur co-doped graphene oxide and multi-walled carbon nanotube (N, S-GCNT), which exhibit good performance for catalyzing oxygen reduction and evolution reactions. These properties are comparable to those of noble-based catalysts such as Pt/C and IrO2, which are attributed to the synergetical effect of doped N, S because they modified the polarity of carbon in the graphene and carbon nanotube. This work provides a simple way to prepare high performance carbon-based metal-free catalysts for the applications in energy-related reactions. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.