Bamboo-like carbonitride nanotubes with multi-type active sites for oxygen reduction reaction in both alkaline and acid mediums

To omni-directionally utilize carbon-based material in nanoscale and improve its catalytic activity for oxygen reduction reaction (ORR), bamboo-like carbonitride nanotubes (bCNTs) with high-density multi-type active sites ([email protected]–N-bCNT) are facilely synthesized via a multi-step method referring to thermal pyrolysis of Co2+ complexed melamine, acid leaching and second annealing. Multi-type active sites including encapsulated Co nanoparticles, intercalated Co/CoO species, Co-Nx coordinated sites and defect-rich surface are present in the as-prepared [email protected]–N-bCNT electrocatalyst. The types and densities of these active sites are easily tuned via the ratio of melamine to Co2+ in precursors and subsequent treatment. Due to the high-density multi-type active sites and bamboo-like tubular structure, [email protected]–N-bCNT electrocatalyst exhibits high catalytic activity for ORR with high stability in both alkaline and acid electrolytes. Quasi-solid-state zinc air battery (ZAB) assembled with the [email protected]–N-bCNT as the cathode exhibits open circle voltage of 1.39 V and peak power density of 14.9 mW cm−2. Two-cell series of quasi-solid-state ZABs can light LED indicator for 7 h, suggesting its promising practical application. The studies provide facile strategy to design the carbon-based electrocatalysts with high performance and tune their active sites.