Microwave Assisted Sol-Gel Synthesis and Characterization of M-TiO2 (M = Pt, Au) Photocatalysts

Pt-TiO₂ and Au-TiO₂ photocatalysts have been synthetized by a microwave assisted sol-gel method and characterized by means of X-ray diffraction (XRD) techniques and UV-Vis diffuse reflectance spectroscopy. Particle sizes have been determined by means of Scherrer equation. Depending on the weight percentage of dopant, some changes in the band gap energy can be observed. X-ray diffractions patterns were recorded to study the formation of TiO₂ crystalline species. The diffraction peaks detected after the calcination process indicate the presence of the crystalline anatase phase and no presence of rutile phase was observed. For the Pt-TiO₂ sample, the peaks detected in 2θ (39.4°, 45.9°, and 67°) indicate the presence of particles of metallic platinum. For the Au-TiO₂ sample, the peaks detected in 2θ (38°, 44.2°, 64.4°, and 77.2°) indicate the presence of particles of metallic gold. The Pt-loaded samples have a crystal size slightly smaller than the Au-loaded samples, from 3.09 to 4.74 nm. UV-Vis DSR technique was used to study the influence of metal load and type. The band gap decreases according to the metal load; it shows that at higher metal load (5 %) the band gap changes from 3.2 eV (pure TiO₂) to 2.98 eV and 3.04 eV for the samples loaded with gold and platinum, respectively. For the Pt-TiO₂ sample, the band gap varies from 3.04 eV (5 wt.%) to 3.2 eV (0.1 wt.%), the same behavior is found on the Au-loaded samples, with a band gap energy variation from 2.98 eV (5 wt.%) to 3.21 eV (0.01 wt.%).