Chemical activation of commercial CNTs with simultaneous surface deposition of manganese oxide nano flakes for the creation of CNTs-graphene supported oxygen reduction ternary composite catalysts applied in air fuel cell

Highlights: • Commercial CNTs-supported oxide coaxial catalysts involved graphene nano structure. • The CNTs were structurally "activated" with a mild conventional wet chemical method. • Working performances of assembled metal air fuel cells exceeded the targeted. • A pioneering work employed binary catalyst supports from one single carbon source. To elevate power performance is crucial for commercally potential metal air fuel cells. Non-precious metal oxide-based oxygen reduction catalytic electrode is much desirable. Rational combination with low-dimension nanomaterials are greatly expected as the supports. Herein, carbon nanotubes (CNTs)-graphene supported manganese oxides composite catalysts (CMnCs) were obtained through activating commercial CNTs, namely, immersing them in acidic KMnO₄ solution at room condition. It avoided conventional hydrothermal process and template surfactants. CMnCs-based air cathodes were made via pilot manufacture technology and equipped in fuel cells. Through characterizations, CNTs was found structurally defective and their outer walls suffered cracking into graphene nano pieces during processing, which further enhanced oxygen reduction reaction (ORR). Nano sized manganese oxide flakes were simulataneously grown on the CNTs-graphene surfaces, identified as the manganite. The areal distribution was found closely related to the additive amount of KMnO₄ with regard to CNTs, somewhat influencing catalytic performance. The ORR activities of these CMnCs exceeded raw CNTs and referred manganese catalysts under identical conditions, and also the CMnCs air fuel cells were capable of outputting ∼15% more power at 100 mA/cm². This reseach provided an inspiring pilot evidence for updating air fuel cell power from economical carbon as well as industrialization.