Effect of Pd addition on the nanostructure and properties of Pd/TiO ₂ catalysts for the photocatalytic degradation of 4-chlorophenol

In this work, the effect of Pd addition on nanostructured TiO₂ powders is studied. The materials were obtained by the sol-gel method and characterized by XRD, Rietveld refinement, TEM, Raman and UV-vis spectroscopies. The crystal structure and the nature of the different TiO₂ phases were modified by varying the palladium/TiO₂ ratio: 0.01, 0.03, and 0.05. The XRD results revealed the presence of different combinations of TiO₂ (B), anatase, rutile and PdO phases as well as their coexistence in the different samples. The Rietveld analysis showed that the composition of the phases is rather affected by the amount of Pd added to the TiO₂ structure. The Raman spectroscopy confirmed the characteristic bands of the TiO₂ phases in the samples and their variation depending on the Pd/TiO₂ ratio. The TEM results indicated that the as-prepared samples displayed crystal sizes of nanometric order (< 80nm). The observed reduction of the band gap was also correlated with the combination of phases due to the palladium addition. All the Pd/TiO₂ samples showed a significant improvement in the elimination of 4-chlorophenol during the application of water treatment technology.