Sol–gel preparation, structural, thermal and spectroscopic analyses, and opto-electronic and photocatalytic activities of normal spinel nickel cobaltite nano-powder for photo-degradation of Reactive Red RB

Abstract

Nickel cobaltite nano-composites have been prepared by a modified sol–gel process using nickel–cobalt acetates as precursors and citric acid-monoethylene glycol as stabilizers followed by calcination at 400 and 650 °C in air. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and thermogravimetry (TG-DTG), and energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) and UV–Vis diffuse reflectance (UV–Vis DRS) spectroscopies were used for structural, thermal, and opto-electronic characterization of the prepared nano-powders. XRD results showed that using acetate as precursor and calcination at 400 °C results in a pure nickel cobaltite phase (NiCo2O4), while at 650 °C, nickel cobaltite with NiO impurity is produced. The nano-structured nickel cobaltite photocatalyst was composed of nano-size crystalline phases with an average size of 25 nm. The optical band gap energy of the nano-structured nickel cobaltite photocatalyst was 2.00 (640) and 3.20 eV (387.5 nm) from the UV–Vis DRS absorption spectra. The photo-catalytic activity of the synthesized nickel cobaltite nano-composite photo-catalysts for degradation of Reactive Red RB azo textile dye was examined. The nano-structured nickel cobaltite photocatalyst exhibited high photocatalytic activity for the photo-degradation of Reactive Red RB which is related to the optical absorption in the visible (640 nm) and UV (387.5 nm) irradiation, electron–hole separation and high surface area of the nano size particles (average size of 25 nm). © 2017, Springer Science+Business Media New York.