The Influence of the Ratio of Au and Pt Nanoparticles in Ternary Composites with TiO2

In the present work, ternary composites were synthesized from commercial titanias (Evonik Aeroxide P25, Aldrich anatase-AA and Aldrich rutile-AR) and two noble metals (gold and platinum). This research focuses on the composition of the photocatalysts, especially on the noble metals. The ratio between the noble metals varies from 0.25 to 0.75% in each composite for each noble metal. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS) measurements were carried out to investigate the structural and optical properties. From the TEM, it can be observed that the particle sizes of the noble metals were between 1 and 4 nm, while the (anatase and rutile) crystals of P25 were 20-40 nm. The XRD showed that the semiconductors' composition remained unchanged during/after the deposition of noble metal nanoparticles. By the DRS measurements, using the Kubelka-Munk equation, it can be concluded that the deposition of the noble metal nanoparticles resulted the decrease of the bandgap energies of the titanias. The photocatalytic activity was investigated under the irradiation of UV light. Oxalic acid and salicylic acid were used as model pollutants. The hydrogen production capacity was investigated as well, where the sacrificial agent was oxalic acid, and UV irradiation was used.