The innovative core-ring structured NiCo2O4 nanoplatelets were found to be novel and promising photocatalysts. The physical and photophysical properties of the photocatalyst were characterized by SEM, TEM, XPS, UV−vis absorption, and photoluminescence, respectively. The core-ring NiCo2O4 nanoplatelets were composed of much smaller nanocrystallines, with an average size of 80−150 nm, compared to the ordinary NiCo2O4 prepared through a conventional hydroxide decomposition method. Moreover, the optical band gap energies of the core-ring NiCo2O4 nanoplatelets were estimated to be 2.06 and 3.63 eV from the UV−vis absorption spectra. The core-ring structured NiCo2O4 photocatalyst exhibited a much higher photocatalytic activity for the degradation of methylene blue than the ordinary NiCo2O4 and TiO2 under visible light irradiation (>420 nm). This enhanced photocatalytic activity of the core-ring NiCo2O4 nanoplatelets was attributed to their higher optical absorption ability, smaller particle size, and more active internal electron transitions. On the basis of all the results, the band structure of the photocatalyst was discussed.

Photophysical and Photocatalytic Properties of Core-Ring Structured NiCo2O4 Nanoplatelets