Influence of Phases Content on Pt/TiO₂, Pd/TiO₂ Catalysts for Degradation of 4-Chlorophenol at Room Temperature

Different Pt/TiO₂ and Pd/TiO₂ catalysts were prepared by sol-gel method. The influence of different amounts of noble metals (1-5 mol-%) present on the microstructure as well as the photocatalytic property under 4-chlorophenol degradation was evaluated. The anatase phase was favored at low Pt content; however, the apparition of new phases after 3 mol-% (PtO) suggests a saturation lattice considering our solubility limit at 1 mol-%. Similar trend was observed when Pd was added to the TiO₂ lattice. The as-prepared catalysts were deeply characterized by X-ray diffraction (XRD) with the Rietveld Method, Raman spectroscopy, high resolution scanning electron microscopy (HRSEM), scanning transmission electron microscopy (STEM), Brunauer-Emmett-Teller (BET) adsorption analysis, and X-Ray photoelectron spectroscopy (XPS). Unit-cell parameter of TiO₂ phases varied from 30 to 93 vol-% depending on the amount of Pt or Pd added to the composite. HRTEM and HRSEM identified the phases in the catalysts and confirmed the nanometric size and morphology of the catalysts. An improvement in removal efficiency of 4-chlorophenol was obtained in all the specimens compared with the commercial Degussa P25, which can be explained in terms of phase composition and modification of the band gap.