Structural, chemical, optical and photocatalytic properties of Zr co-doped anatase-rutile mixed phase TiO2: Ag nanoparticles

Abstract

Zr co-doped TiO2:Ag nanoparticles were synthesized by the co-precipitation method and the influence of Zr co-dopant with varying content on the structural, optical and photocatalytic properties of TiO2:Ag photocatalysts was investigated. X-ray diffraction and Raman spectroscopy confirmed the anatase-rutile mixed phase of TiO2 and Zr content eased the anatase-rutile phase transformation. X-ray diffraction peak shift with Zr content indicated the substitutional doping of Zr4+ ions into TiO2 lattice. The optical properties of the nanoparticles were investigated with diffuse reflectance spectroscopy, photoluminescence and Fourier transform infrared spectroscopy. Zr dopants induced the Burstein-Moss effect, resulting in the broader bandgap and photoluminescence shift. X-ray photoelectron spectroscopy was utilized to reveal the surface chemical environment of the Zr co-doped TiO2:Ag nanoparticles and found the presence of Zr4+ ions on the photocatalyst surface, which act as electron traps. The dependence of operational parameters such as photocatalytic load, dye concentration and pH on Zr co-doped TiO2:Ag nanocatalyst was also monitored. The photocatalysts demonstrate improved photocatalytic activity toward methylene blue degradation with maximum efficiency achieved by the photocatalyst having the highest Zr content. 20 mg and 10.35 μM were found to be the optimum values for photocatalytic load and initial methylene blue concentration, respectively. Further, at alkaline pH, complete decolorization of the reaction mixture was observed in only 60 min with 92.6% efficiency by highest co-doped photocatalyst. The effect of Zr content on degradation rate with different parameters was also explored with a possible mechanism to understand the effect of dopants on photocatalytic activity of the photocatalysts.