Synthesis of a heterojunction CoTiO/CoO nano-composite thin film with superior photocatalytic activity and reusability: Effect of calcination temperature on phase transformation and effect of oxidants on enhanced degradation of Indo Light Blue dye.

CoTiO/CoO heterojunction nano-composite was grown by a coprecipitation method at low temperature. The effects of calcination temperature on the phase composition, crystallization and morphology of the cobalt titanates were also examined. Notably, the novel nano-crystalline cobalt titanate with a narrow band gap to coulpe with cobalt oxide (CoO) by a direct coprecipitation method (CoTiO/CoO) was attained. The Nano-crystalline samples were systematically characterized by TG/DTG, XRD, DRS, FESEM, FT-IR, EDX and XPS techniques. The results showed that CoTiO/CoO nano-composite hetero-junction was formed at 650 °C, while at 750 °C a single phase CoTiO nano-crystal was prepared. Photocatalytic activities indicated the heterostructured CoTiO3/CoO nano-composite exhibited much higher photocatalytic activity for degradation of Indo Light blue under visible light irradiation with added oxidants (KSO, KBrO, and HO). The charge separation of CoTiO3 and CoO would result the enhanced visible-light harvesting ability and longer lifetime of photogenerated charge carriers. The stability and reusability of catalysts during four successive cycles were resulted. Finally, a possible mechanism responsible for the charge separation and improved photocatalytic activity was proposed.