TiO2 nanocrystallites photocatalysts modified with metallic species: Comparison between Cu and Pt doping

Abstract

In this work, TiO2 nanoparticles were modified with different Cu and Pt species: metallic nanoparticles and ions. The photocatalysts were prepared via a sol-gel process by peptization with HNO3 at low temperature (i.e. <100 °C). The metallic nanoparticles were prepared by NaBH4 reduction from the corresponding metallic salts. For the ion modification, metallic salts were just added during the synthesis of the TiO2. The materials were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, diffuse reflectance, and X-ray photoelectron spectroscopy (XPS). The results showed that the TiO2 materials were mainly composed of anatase phase with a small amount of brookite phase. The nanoparticle size was in the range of 4–8 nm leading to high specific surface area (i.e. >200 m2 g−1). The absorption property of these materials showed a visible sensitization for all samples even the pure TiO2 compared to the Evonik P25 due to N-doping confirmed by XPS analysis.The photocatalytic activity on the degradation of p-nitrophenol (PNP) showed an increase in the efficiency for nearly all catalysts compared to the pure one. Some mechanisms were proposed to explain these modifications of activity with doping. Under visible light, the photocatalysts were up to 5 times more efficient than P25 (for the best sample composed of Cu metallic nanoparticles).