Thin film technology has made significant contributions to the field of photocatalysis through improvements in surface properties and a decrease in material costs. Therefore, the present study aims to evidence the properties that Pd can confer to TiO₂ thin films prepared by chemical vapor deposition technique and to verify their effectiveness as photocatalysts in the degradation reaction of the carbinol-based malachite green dye. TiO₂ films with different nominal Pd contents (2.8, 3.7, 4.6, and 6.4 at. % Pd) synthesized by CVD at 400 °C and 1 Torr pressure exhibit significant changes in their crystal structure, morphology, and electronic properties. On the one hand, at low concentrations (2.8 and 3.7 at. % Pd), substitutional doping is promoted. In contrast, the increase in concentration (4.6 and 6.4 at. % Pd) encourages the formation of PdO and PdTiO₃ phases, as indicated by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy results. The anatase phase is partially inhibited by other phases, such as Pd–O and Ti-Pd–O; consequently, the grain size that constitutes the film is considerably reduced, and microstrains are increased. On the other hand, the study of the optical properties reveals a decrease in the bandgap energy and the recombination velocity of the charge carriers, resulting in a maximum degradation of 67% of the dye, which is obtained with film 4.6 at. % Pd, attributed to a synergistic effect between the observed properties.

Au nanoparticles were supported on TiO₂ nanotubes by a novel vapor phase impregnation approach (VPI) using gold dimethyl-acetylacetonate as a precursor. This study aimed to evaluate the capacity of these materials in the photodecoloration of malachite green dye, with the vision to correlate the chemical, structural, morphological, and optical properties with its photocatalytic performance. The photocatalysts were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectronic spectroscopy (XPS), electronic microscopy (HAADF-STEM and HRTEM), and UV–vis spectroscopy. The techniques mentioned above made it possible to detect the presence of small gold nanoparticles (around 3.1 nm), with a high apparent dispersion even at high metal loading for all analyzed systems. According to the XPS results, the Au nanoparticles remain reduced (Au°), and they have a high electronic interaction with TiO₂, which eventually originates an electronic exchange between them and consequently a decrease in the band gap energy. In addition, the surface plasmonic resonance observed through UV–vis spectroscopy of the Au nanoparticles are factors that can be related to the high decoloration observed in these photocatalysts, specifically in the 15 wt% Au material, which achieves maximum photodecoloration of malachite green dye at 93%.