Synthesis of cobalt doped nickel titanate nanomaterials for enhanced photocatalytic reduction of chromium

Abstract

A series of cobalt doped nickel titanate nanomaterials where cobalt % is varied from 1 to 10% have been successfully synthesized by solvothermal method followed by calcination at 600 °C. Synthesized materials are characterized by XRD, FE-SEM, HR-TEM, BET surface area, DRS UV-Vis-NIR, XPS and PL spectroscopy. XRD and HR-TEM confirm the existence of NiTiO3 ilmenite structure with crystallite size in the range of 20–30 nm. HR-TEM of cobalt doped NiTiO3 shows the presence of tiny single atom cobalt metal sitting on NiTiO3, surface which induces the surface plasmon resonance effect. XPS of the doped NiTiO3 exhibits Ti3+ formation accompanied with oxygen vacancies resulting in the extended light absorption in the Vis-NIR region. The photocatalytic efficiency is studied monitoring the photoreduction of carcinogenic Cr (VI) under visible light. 3% cobalt doped NiTiO3 achieves 100% reduction of 30 ppm Cr (VI) solution within 60 min whereas pristine NiTiO3 shows only 50% efficiency under identical conditions. The trapping experiment shows the direct transfer of photogenerated electrons for the reduction of Cr (VI) following a first order kinetics. The two-fold enhanced activity of cobalt doped NiTiO3 is due to the collective effect of oxygen vacancies, efficient Vis-NIR absorption and surface plasmon resonance effect.