Structural characterization and photocatalytic properties of hydrothermally synthesized Ni2+-TiO2 nanoparticles for dye degradation under direct sunlight

Abstract

A Ni²⁺-TiO₂ photocatalyst, efficient and highly active in sunlight has been prepared by a simple hydrothermal method using titanium isopropoxide (TTIP) precursor. The synthesized nanoparticles (NPs) have been analysed to determine its structural, optical, morphological and compositional properties using X-ray diffraction, Raman, UV-DRS, photoluminescence, XPS, TEM and EDS. The EDS micrograph confirms the existence of Ni²⁺ atoms (0.65, 1.32 and 1.60 wt.%) in the TiO₂ matrix. The average particle size obtained from TEM is 8-11 nm and is in good agreement with XRD results. Raman bands at 641.44 cm^-1, 517.42 cm^-1 and 398.43 cm^-1 further confirm pure phase anatase in all samples. XPS shows the substitution of Ti⁴⁺ ions by Ni²⁺ ions in the TiO₂ host lattice. The photocatalytic activity of these nanoparticles have been studied using malachite green dye under UV light, visible light and direct sunlight. The crystallite size and band gap decreases with increase in Ni²⁺ concentration which increase its catalytic activity under sunlight. The photocatalyst, Ni²⁺-TiO₂ (1.60 wt.%), shows excellent photocatalytic activity in the visible and direct sunlight and hence it is a promising for environmental friendly photocatalytic applications.