Amorphous hierarchical NiCo2O4–CoNiO2hybrids have been successfully fabricated<italic>via</italic>a facile one-pot hydrothermal route, followed by morphologic conversion into urchin-like structured NiCo2O4–CoNiO2nanorods and irregular-shaped hierarchical NiCo2O4–CoNiO2polyhedral nanocrystals through air-annealing treatment at 450 °C and 650 °C, respectively.

Co2+/Co3+ratio dependence of electromagnetic wave absorption in hierarchical NiCo2O4–CoNiO2hybrids