Nickel-Nitrogen Doped MnO2 as Oxygen Reduction Reaction Catalyst for Aluminum Air Batteries.

Aluminum-air battery has the advantages of high energy density, low cost and environmental protection, and is considered as an ideal next-generation energy storage conversion system. However, the slow oxygen reduction reaction (ORR) in air cathode leads to its unsatisfactory performance. Here, we report an electrode made of N and Ni co-doped MnO₂ nanotubes. In alkaline solution, Ni/N-MnO₂ has higher oxygen reduction activity than undoped MnO₂, with an initial potential of 1.00 V and a half-wave potential of 0.75 V. This is because it has abundant defects, high specific surface area and sufficient Mn³⁺ active sites, which promote the transfer of electrons and oxygen-containing intermediates. Density functional theory (DFT) calculations show that MnO₂ doped with N and Ni atoms reduces the reaction overpotential and improves the ORR kinetics. The peak power density and energy density of the Ni/N-MnO₂ air electrode increased by 34.03 mW cm^-2 and 316.41 mWh g^-1, respectively. The results show that N and Ni co-doped MnO₂ nanotubes are a promising air electrode, which can provide some ideas for the research of aluminum-air batteries.