In this work, we have successfully prepared urchin-like NiCo2O4 spheres via a facile
hydrothermal method without any templates or surfactants. The as-prepared urchin-like
NiCo2O4 spheres have uniform diameters of 6 mm with numerous small nanorods
radially-grown from the center. Typical nanorods have diameters of 20e50 nm and
lengths of 2e3 mm. Remarkably, urchin-like NiCo2O4 nanostructure as an alternative nonprecious
metal electrocatalyst for ORR exhibits catalytic performance and excellent
cycling stability in alkaline environment.