▎ 摘　　要

Great efforts have been focused on exploring high-efficiency and stable catalysts towards oxygen reduction reaction (ORR) and reducing the use of polymer binders in cathodes for metal-air batteries. In consideration of synergistic effects, unique porous structure and improved properties, a composite of carbon nanotubes and three-dimensional graphene (CNTs-3D graphene) developed via a well-controlled route is urgently required. Herein, an ultrathin Co3O4 nanosheet clusters anchored on nitrogen-doped carbon nanotubes/3D graphene (NCNTs/3D graphene) composite was prepared by chemical vapor deposition (CVD) along with thermal treatments over a Ni foam substrate. The cyclic voltammetry (CV) and linear sweep voltammograms (LSVs) results indicate that the Co3O4/NCNTs/3D graphene composite possesses remarkable electrocatalytic performance towards ORR in alkaline condition compared with NCNTs/3D graphene, Co3O4/3D graphene, and 3D graphene catalysts, even outperforming the commercial 20 wt% Pt/C catalyst. Moreover, the Al-air coin cell employing Co3O4/NCNTs/3D graphene as binder-free cathode obtains an open circuit voltage of 1.52 V, a specific capacity of 482.80 mAh g(-1) at the discharge current density of 1.0 mA cm(-2), and a maximum power density (P-max) of 4.88 mW cm(-2), which are superior to the Al-air coin cell using Co3O4/3D graphene, Pt/C, and traditional Co3O4/NCNTs/3D graphene electrodes. This work supplies valuable insights to develop scalable binder-free cathodes using NCNTs/3D graphene based electrocatalysts with excellent catalytic activity towards ORR in Al-air systems.