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 activ...