Highly active and thermo-stable anatase TiO2 photocatalysts synthesized by a microwave-assisted hydrothermal method

Abstract

Phase-pure anatase titanium dioxide (A-TiO2) with high thermal stability is synthesized by a microwave-assisted hydrothermal (MAH) method. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, and photoluminescence spectra (PL) analysis. The photo-electrochemical responses are examined via linear sweep voltammetry (LSV), intensity-modulated photocurrent spectroscopy (IMPS), and intensity-modulated photovoltage spectroscopy (IMVS). The photocatalytic activity of TiO2 nanoparticles (NPs) has been confirmed through the methylene blue (MB) de-colorization under the simulated sunlight. The results show that the as-prepared TiO2 nanocrystals possess thermal stability for the anatase-to-rutile phase transformation up to 900 °C. The phase-pure A-TiO2 annealed at 800 °C exhibits a much higher de-colorization rate than the commercially available TiO2 (Degussa P25) powders. The higher photocatalytic activity of this sample is due to its enhanced crystallinity, leading to a lower rate of electron/hole pair recombination and a larger photocurrent density in comparison with all other samples and P25. The sample annealed at 900 °C shows the highest specific activity on MB de-colorization, demonstrating the importance of thermal stability and crystalline phase.