Effects of the Brookite Phase on the Properties of Different Nanostructured TiO2 Phases Photocatalytically Active Towards the Degradation of N-Phenylurea

Different sol-gel synthesis methods were used to obtain four nanostructured mesoporous TiO2 samples for an efficient photocatalytic degradation of the emerging contaminant N-phenylurea under either simulated solar light (1 Sun) or UV light. Particularly, two TiO2 samples were obtained by means of as many template-assisted syntheses, whereas other two TiO2 samples were obtained by a greener template-free procedure, implying acidic conditions and, then, calcination at either 200 °C or 600 °C. In one case, anatase was obtained, whereas in the other three cases mixed crystalline phases were obtained. The four TiO2 samples were characterized by X-ray powder diffraction (followed by Rietveld analysis); Transmission Electron Microscopy; N2 adsorption/desorption at −196 °C; Diffuse Reflectance UV/Vis spectroscopy and ζ-potential measurements. A commercial TiO2 powder (i. e., Degussa P25) was used for comparison. Differences among the synthesized samples were observed not only in their quantitative phase composition, but also in their nanoparticles morphology (shape and size), specific surface area, pore size distribution and pHIEP (pH at isoelectric point), whereas the samples band-gap did not vary sizably. The samples showed different photocatalytic behavior in terms of N-phenylurea degradation, which are ascribed to their different physico-chemical properties and, especially, to their phase composition, stemming from the different synthesis conditions

Solid-state ion exchange of Fe in small pore SSZ-13 zeolite: Characterization of the exchanged species and their relevance for the NOx SCR reaction

Solid state ion exchange was performed for the successful introduction of Fe cations in the small pore CHA structured SSZ-13 zeolite. The produced catalysts were characterized by IR and UV-Vis spectroscopies and thermally programmed reaction techniques to probe the Fe sites formed during the exchange and the catalytic activity for the NOx SCR reaction. The results indicate that highly dispersed and heterogeneous Fe sites are formed, and the type depends on the Al distribution in the zeolite. Dimeric Fe species are formed preferentially at the start of the exchange on the 6- and 8-member rings that contain at least two Al exchange sites and once these sites are fully saturated the Fe is exchanged as isolated cations

Conclusions

The current chapter reports the main conclusions that were drawn during the writing process. Suggestions on how to optimize the experimental methodology for a more accurate comparison between different heterogeneous catalysts are given. The difficulties concerning the issues of the scale up and of the efficiency of novel water splitting cells are addressed, as well. Finally, future perspectives of the solar driven hydrogen production technology are foreseen