Enhanced photo-catalytic degradation of naphthol blue black on nano-structure MnCo₂O₄: charge separation of the photo-generated electron–hole pair

MnCo₂O₄ nano-composite photocatalyst was synthesized via co-precipitation technique. Composite formation of cobalt oxide with manganese was intended to create tail states within the band gap of cobalt oxide for better charge separation of the photo-generated electron–hole pairs in nano-composite photocatalyst. The MnCo₂O₄ nano-composite can effectively mineralize organic contaminants. MnCo₂O₄ nano-composite photocatalyst was characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), transmission electron microscopy, energy dispersive X-ray spectroscopy, fourier transform infrared spectroscopy (FTIR) and UV–Vis diffuse reflectance spectra (UV–Vis DRS). X-ray diffraction analysis showed cubic manganese cobalt oxide MnCo₂O₄. FESEM results showed spherical nanoparticles with cauliflower nanostructure. The mean size of particles was in the ranges of 30–60 nm. The band gap for MnCo₂O₄ nano-composite photocatalyst was 1.95 and 2.49 eV, based on the results of diffuse reflectance spectra. FTIR results showed two type of fundamental absorption bands at 620 and 505 cm⁻¹ due to stretching vibrations of Mn–O and Co–O, respectively. The photo-catalytic activitie of nano-composite photocatalysts were investigated using a naphthol blue black dye as textile dye contaminant and the results showed an outstanding performance yielded 92 % total organic carbon removals attributed to charge separation of the photo-generated electron–hole pairs in nano-composite.