Versatility in the catalytic and photocatalytic reactions of composites based on Zr- and Zr-Pd-doped titania nanoparticles

Abstract A series of Zr-doped titanium oxide-based nanomaterials with different amounts of Zr (1%, 2% and 5%) have been prepared by a simple method based on sol-gel procedures. The materials have been calcined at different temperatures (400, 500 or 600 °C). The calcined materials have been characterised by different methods and the structural features compared and analysed in detail. In general, the incorporation of different quantities of Zr lead to changes in the structural features in terms of morphology, particle size and crystallinity of the sample. The Zr-doped titanium oxide nanomaterials were studied in the photodegradation of a model of organic pollutant such as methylene blue. The results show differences in the photocatalytic activity of the materials with different quantities of Zr and the calcination temperature. In view of the interesting results of photodegradation, the Zr-doped materials were also tested in the oxidation and photooxidation of benzyl alcohol to benzaldehyde. Furthermore, the nanomaterials which showed better catalytic properties were also doped with Pd nanoparticles, which were prepared in situ by reduction of a Pd salt. All the Pd-Zr-doped systems present significant physico-chemical differences with the analogous materials without Pd (changes in the band gap, surface area, crystallite size, and structural agglomeration). The Pd-doped systems were tested in C-C coupling reactions, catalytic and photocatalytic oxidation of benzyl alcohol and photodegradation of methylene blue at different pH values, showing an interesting catalytic and photocatalytic versatility which may be exploited in the future to other catalytic green processes.