▎ 摘 要
Nitrogen-doped graphene-carbon nanotubes (NG-NCNTs) were prepared from multi-walled carbon nanotubes (MWCNTs) and then hybridized with nitrogen-doped nano-onions (NNOs) to fabricate a highly effective carbon-based electrocatalytic material for the oxygen reduction reaction (ORR). The graphene oxide attached on the oxidized MWCNTs (GO-OCNTs), which was formed from the MWCNTs by an oxidation reaction with a strong acid, underwent nitrogen doping with urea to produce the NG-NCNTs. The content of oxygen of the GO-OCNTs was controlled by varying the oxidation time to produce NG-NCNTs with an optimal ORR activity. The NG-NCNTs prepared from GO-OCNTs and oxidized for 6 h showed the best ORR activity. The NG-NCNTs were hybridized with NNOs to further improve their ORR activity. The NNO aggregates were well dispersed among the NG-NCNTs by mixing, and significantly increased the specific surface area of the NG-NCNT/NNO hybrid. As a result, the NG-NCNT/NNO hybrid exhibited a better ORR activity than the NNOs and NG-NCNTs. The current density of the NG-NCNT/NNO hybrid was comparable to that of the platinum-based catalyst (Pt/C). A carbon-based catalyst with a high ORR activity and long-term stability could be produced by hybridizing NG-NCNTs and NNOs. (C) 2018 The Electrochemical Society.