Pitch-encapsulated Ni/Ni3C anchored on ammonia-activated carbon nanotubes for high-performance zinc-air batteries

The improvement of rechargeable zinc-air batteries is still limited by the sluggish oxygen electrochemistry at the air cathode, where both the oxygen reduction and oxygen evolution processes need to be accelerated. In this work, a Ni/Ni 3 C composite was obtained by thermal treatment using ammonia-activated carbon nanotubes as the conductive backbone and coal tar pitch as a supplementary carbon precursor. Ni and Ni 3 C nanoparticles are anchored on the nanotube framework, and part of their surface is wrapped by graphitized carbon. Such a multiphase architecture builds efficient electron-transport channels, reinforces the coupling between the Ni-based species and the carbon matrix, and improves structural robustness under electrochemical conditions. The catalyst therefore shows strong bifunctional oxygen electrocatalytic activity, giving a half-wave potential of 0.86 V for ORR and an overpotential of 250 mV at 10 mA·cm −2 for OER, together with satisfactory durability. When assembled as the air cathode of a rechargeable zinc-air battery, it affords an open-circuit voltage of about 1.42 V, a peak power density of 195 mW·cm −2 , and stable cycling for more than 200 h at 5 mA·cm −2 . DFT calculations indicate that nitrogen-containing interfacial sites reshape the local charge distribution and improve the adsorption and conversion of oxygen intermediates, which is favorable for both ORR and OER.