Effect of intermediate ball milling on the synthesis of Cu-doped TiO2 nano-photocatalyst by sol–gel method

Abstract

In this paper, Cu-doped TiO2 powder was prepared by sol–gel method and the influence of 1 h intermediate ball milling before calcination on different properties was investigated. The powders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and ultraviolet–visible spectrophotometer. Ball milling before calcination for 1 h was sufficient enough to accelerate the calcination process and obtain small size of the powder particles. Calcined ball milled sample at 450 °C for 2 h revealed anatase TiO2 phase structure with average particle size of 180 nm. The results showed that the synergistic effect of Cu doping and ball milling before calcination considerably narrowed the band gap of the synthesized TiO2 photocatalyst to 2.85 eV. PL results confirmed an effective separation of electron-hole pairs by Cu doping and also intermediated ball milling. The best photocatalytic performance under visible light in degradation of methylene blue (MB) was achieved with the combined influence of ball milling before calcination and Cu doping on TiO2, whereby a degradation of about 66% was obtained. It was found that the degradation reactions of MB by prepared photocatalysts followed the pseudo-first order reaction kinetics. In comparison, ball milling of TiO2 and Cu-doped TiO2 after calcination showed the undesirable effect on photocatalytic performance. In addition, nano-photocatalyst showed the good stability under visible light after recycling.