Cysteine modified anatase TiO2 hollow microspheres with enhanced visible-light-driven photocatalytic activity

Abstract

Preparation of visible-light responsive TiO2 photocatalyst for recycling and repeated use is of great importance in practical application, such as water purification. In this paper, anatase TiO2 hollow microspheres were prepared using Ti(SO4)2 and NH4F as the starting materials, which were then mixed with cysteine, a biomolecule, followed by calcination at 300°C for 2h. The cysteine modified TiO2 hollow microspheres were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption isotherms, UV–vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, photoluminescence and photocurrent. The photocatalytic activity of cysteine modified TiO2 hollow microspheres was evaluated using Brilliant Red X3B, an anionic azo dye, as the target organic molecule under visible light irradiation (λ≥400nm). The experimental results showed that C, N and S elements were doped into the lattices of TiO2 hollow microspheres, resulting in an obvious increase in visible-light harvesting ability. With increase in the molar ratio of cysteine to titania (R) from 0 to 2.0, the visible-light photocatalytic activity of the samples increase first, and then decrease. The photocatalyst with R=1.0 shows the highest photocatalytic activity, which is 6 and 4 times higher than that of pristine TiO2 counterpart and commercial P25 photocatalyst, respectively. The enhanced photocatalytic activity of cysteine modified TiO2 hollow microspheres is attributed to the synergistic effects of improved visible-light harvesting ability, enhanced adsorption to organic pollutant and increased efficiency in separation of the photo-generated electron and hole.