Influence of structural and surface characteristics of Ti1-xZrxO2 nanoparticles on the photocatalytic degradation of methylcyclohexane in the gas phase

In the present work, we investigate the influence of the physicochemical characteristics of Ti1-xZrxO2 nanoparticles with anatase structure on the photocatalytic activity for the elimination of methylcyclohexane in the gas phase. Samples with a molar content of Zr ranging from 0 to 16% were prepared by an inverse microemulsion method. Additionally, a sample of ZrO2 supported on TiO2 (5.2% molar content of Zr) was obtained in a two-stage synthesis using the same microemulsion procedure. The structural and electronic properties of these materials were determined by a multitechnique approach using X-ray diffraction as well as Raman, XANES, EXAFS, and UV-vis spectroscopies. FTIR spectra of the catalysts before and after photocatalytic experiments were also carried out in order to evaluate the possible changes on the surface upon photoreaction. In addition, surface characteristics of these nanoparticles were determined by means of N-2 adsorption isotherms and NH3 adsorption microcalorimetry. XRD and XAS results indicate that the anatase-type structure is maintained throughout the Ti-Zr series, although noticeable changes in the local order are detected for samples above/below 6 % zirconium. All Ti1-xZrxO2 samples show a significant enhancement of the photocatalytic activity with respect to both TiO2 and the ZrO2/TiO2 sample at high relative humidity. In contrast, Ti-Zr catalysts exhibit higher deactivation under dry conditions than pure titania. These observations are discussed in relation to the structural and electronic modifications of the anatase nanoparticles induced by Zr incorporation.