Improved photocatalytic activity of gold decorated differently doped TiO₂ nanoparticles: A comparative study

In this paper, undoped and several differently doped (with Fe(3+), N(-), and γ-Al2O3) TiO2-nanoparticle-based photocatalysts and those covered with ultrasmall gold nanoparticles (AuNPs) were engineered. Their photocatalytic performance was studied by utilizing them for the liquid-phase decomposition of the model dye methylene blue (MB) under visible-light irradiation. The structural, morphological, physico-chemical, and optical properties of the photocatalysts were investigated using X-ray diffraction, X-ray photoelectron spectroscopy, diffuse-reflectance UV-Vis absorption spectroscopy, Raman spectroscopy and transmission electron microscopy. Photodegradation kinetics of MB was followed by measuring the absorbance of MB at 664 nm at different irradiation times, whereas the mineralization of MB was examined by determining the total organic carbon (TOC) content. The photocatalytic activity of TiO2 nanoparticles was shown to be significantly increased by introducing dopants into the crystal lattice and depositing AuNPs on the surface. Among those, γ-Al2O3 doped TiO2 nanoparticles covered with deposited AuNPs show the best photocatalytic performance. Altogether, the here engineered photocatalysts as consisting of doped TiO2 nanoparticles decorated with AuNPs establish novel three-component nanocomposite systems, where synergetic interactions between surface AuNPs, dopants and TiO2 were shown to significantly enhance the photocatalytic activity.