Three-dimensional Composite Catalysts for Al–O₂ Batteries Composed of CoMn₂O₄ Nanoneedles Supported on Nitrogen-Doped Carbon Nanotubes/Graphene

Great efforts have been focused on studying high-efficiency and stable catalysts toward oxygen reduction reaction (ORR) in metal–air batteries. In view of synergistic effects and improved properties, carbon nanotubes and three-dimensional graphene (CNTs-3D graphene) hybrid catalysts developed via a well-controlled route are urgently required. Herein, a CoMn2O4 (CMO) nanoneedle-supported nitrogen-doped carbon nanotubes/3D graphene (NCNTs/3D graphene) composite was prepared by in situ chemical vapor deposition (CVD) along with hydrothermal methods over a Ni foam substrate. The cyclic voltammetry and linear sweep voltammograms results indicate that the CMO/NCNTs/3D graphene hybrid possesses remarkable electrocatalytic performance toward ORR in alkaline conditions compared with NCNTs/3D graphene, CMO/3D graphene, and 3D graphene catalysts, even outperforming the commercial 20 wt % Pt/C catalyst. Moreover, the Al–air coin cell employing CMO/NCNTs/3D graphene as cathode catalysts obtains an open circuit voltage of 1.55 V and a specific capacity of 312.8 mA h g–1, which are superior to the Al–air coin cell with NCNTs/3D graphene as catalysts. This work supplies new insights to advanced electrocatalysts introducing NCNTs/3D graphene as a catalyst support to develop scalable transition-metal oxide/NCNTs/3D graphene hybrids with excellent catalytic activity toward ORR in Al–air systems.