▎ 摘　　要

Bifunctional catalyst, which presents excellent electrocatalytic activity for oxygen reduction/evolution reaction (ORR/OER), is the key factor to explore the rechargeable Zn-air batteries (ZABs) with excellent performance and high stability. Herein, the polyaniline is coated on the outer surface of N-doped graphene hollow spheres (NGHS), which can further form the N-doped carbide (CNx) through the high temperature calcination process. The prepared CNx decorated N-doped graphene hollow spheres (CNx-NGHS) could enhance the conductivity of substrate material caused by the doping of N atoms, and the stretchy 3D hollow structure can prevent the deformation and collapse of fabricated electrode catalyst during the charge/ discharge processes. Furthermore, the doped N atoms, acting as active sites, could facilitate the nucleation and growth of the core/shell metals/oxides nanoparticles on the surface of the CNx-NGHS, and at the same time enhance the interaction between metals/oxides nanoparticles and CNx-NGHS, both of which are helpful for promoting the electrocatalytic activity. Based on the investigation results, it can be concluded that CNx-NGHS loaded Co/CoO core/shell nanoparticles (Co/CoO/CNx-NGHS) show obvious better bifunctional electrocatalytic performance than that of CNx-NGHS supported Ni/NiO core/shell nanoparticles (Ni/NiO/CNx-NGHS). The synthesized Co/CoO/CNx-NGHS presents the lowest Delta E (similar to 0.728) (Delta E= E-j10-E-1/2), which indicates the better bifunctional electrocatalytic activity. The ZAB equipped with the Co/CoO/CNx NGHS catalyst can deliver a maximum power density of 117 mW cm(-2), which is larger than that of commercial 10% Pt/C (95 mW cm(-2)). The specific capacity of the Co/CoO/CNx-NGHS at both 100 and 200 mA cm(-2) can reach similar to 99% of the theoretical capacity (824 mAh g(-1)). Moreover, a minimum visible voltage loss can be seen for the synthesized Co/CoO/CNx-NGHS after cycled for 100 h, indicating the good durability and stability. All investigated results demonstrated that the outperformance of the fabricated Co/ CoO/CNx-NGHS catalyst makes it a potential choice to replace the noble metal/carbon-based materials. (C) 2021 Elsevier B.V. All rights reserved.