Self-supported N-doped NiSe2 hierarchical porous nanoflake arrays for efficient oxygen electrocatalysis in flexible zinc-air batteries

Rational design of efficient bifunctional air cathodes towards oxygen evolution/reduction reaction is of central importance for energy-efficient metal-air batteries, but remains an ongoing challenge. Here, N element doped NiSe2 nanosheets in-situ grown on the carbon cloth were prepared via facial hydrothermal synthesis of nickel hydroxide followed by selenization and nitrogen doping treatment. Such self-supported N-doped NiSe2 nanoarrays (N-NiSe2/CC) exhibits superior bifunctional catalytic activity and high durability compared with the pristine NiSe2/CC, which are ascribed to the unique structure after nitrogen doping. Nitrogen doping can provide more electrocatalytical active sites and improve the electronic transport for fast reaction kinetics, which is preferably corroborated with density functional theory calculations and X-ray absorption spectroscopy. As a proof of concept, the solid-state zinc-air batteries assembled by the N-NiSe2/CC directly as the air cathode present a low overpotential of 0.75 V, remarkable cyclic stability of 30 h with 90 circles, and robust flexibility. Therefore, the N-NiSe2/CC system proves to be a highly active and reliable electrode for the developing of metal-air batteries, opening up a promising opportunity for high-performance portable electronics.