Mesoporous Au/TiO2 composites preparation, characterization, and photocatalytic properties

In this work, mesoporous Au/TiO2 composites have been synthesized and tested on photodegradation of methylene blue dye solution. Mesoporous TiO2 prepared at 450 °C using triblock polymer F127 as structure-directing agent was applied as substrate, while various HAuCl4 concentrations were used for Au loading through deposition-precipitation method using urea as precipitator and hydrogen reducing process. The influences of Au loading on the microstructures of mesoporous TiO2 including degree of dispersion, particle size, surface area, light absorption, and band gap were studied with transmission electron microscopy (TEM), X-ray diffraction (XRD), diffuse reflection infrared Fourier transformed spectroscopy (DRIFT), N2 adsorption–desorption isotherm analysis (BET), and UV–Vis diffuse reflectance spectra. With Au loading, the size of TiO2 nanoparticles in Au/TiO2 composites is similar as that of TiO2 substrate. However, the degree of dispersion was greatly improved. Furthermore, an obvious surface plasmon resonance centered at 570 nm was found in UV–Vis diffuse reflectance spectra for Au/TiO2 composites. Au loading also induced an obvious red shift of light absorption from UV region to visible region and strengthened both UV and visible light absorption in contrast to substrate. Photodegradation results verified that photocatalytic activity of mesoporous TiO2 was improved by Au loading. 0.25%Au/TiO2 composite showed the highest activity, which may be ascribed to its high surface hydroxyl content and the formed Schottky junction after Au loading. These results suggested that noble metal modification is a promising way to synthesize photocatalysts with both high activity and visible light sensitivity.