Search results for "Fondamenti"
showing 10 items of 542 documents
EPR investigations of polymeric and H2O2 -modified C3N4 -based photocatalysts
2019
The C3N4 -based nanopowders prepared by thermal condensation of melamine (MCN) with subsequent thermal etching (MCN-TE) and H2O2 -treatment were investigated by Q- and X-band EPR spectroscopy in dark and upon in situ UVA or visible-light exposure. Lorentzian signal at g = 2.003, more pronounced in the case of the thermally etched material, dominates EPR spectra of MCN and MCN-TE. More complex spectra were found for H2O2 -treated photocatalysts revealing the presence of signals attributed to the radicals produced via H2O2 interaction with C/N sites in the C3N4 polymeric network. The X-band spectra monitored upon in situ irradiation of the C3N4 -based photocatalysts evidenced the intensity gr…
Overview on photoreforming of biomass aqueous solutions to generate H2 in the presence of g-C3N4 based materials
2023
Photoreforming (PR) of biomass can be considered a viable technology under mild experimental conditions to produce hydrogen with a high reaction rate using compounds from renewable resources and waste materials. The application of biomass PR gives rise to both hydrogen generation and biomass waste valorization. The process could be scaled up to obtain hydrogen under natural sunlight irradiation, and research on polymeric carbon nitride (g-C3N4)-based photocatalysts has been widely carried out in recent years. The non-metallic-based carbon nitride materials are economical and (photo)stable polymer semiconductors, and their physicochemical surface and electronic properties are optimal for obt…
Photocatalysis: Applications
2016
Heterogeneous photocatalysis is a sustainable technology mainly employed for water and air cleaning purposes. However, in the last two decades a lot of attention has been given to photocatalysis as an alternative route to be used in place of traditional industrial processes. The sustainability of photocatalysis mainly comes from the exploitation of renewable sources, such as solar light, and the possibility to avoid unsafe reagents/solvents and severe temperatures and pressures. In this chapter we give a critical presentation of some case studies concerning the use of heterogeneous photocatalysts, such as modified and bare TiO2, ZnO, ZnS, WO3, titanium silicalite, V2O5, polyoxometalates, Cd…
Photocatalytic glucose conversion to produce hydrogen in the presence of TiO2 based materials.
2015
In the present research commercial anatase (BDH) and anatase/rutile (P25) and home prepared anatase (HPA), rutile (HPR) and brookite (HPB) TiO2 polymorphs and have been used as supports for the deposition of metallic Pt. The Pt-TiO2 samples have been tested in the glucose conversion under anaerobic conditions. The presence of Pt resulted essential for the production of H2 and the home prepared samples resulted more active than the commercial ones.
Keggin heteropolyacid supported on TiO2 used in gas-solid (photo)catalytic propene hydration and in liquid-solid photocatalytic glycerol dehydration
2017
Abstract (Photo)catalytic propene hydration to 2-propanol and glycerol dehydration to acrolein were carried out by using Keggin heteropolyacids (HPAs) supported on TiO 2 . Binary materials have been prepared by impregnation of H 3 PW 12 O 40 , H 3 PMo 12 O 40 and H 4 SiW 12 O 40 , on TiO 2 Evonik P25. Moreover, a binary material consisting of H 4 SiW 12 O 40 and TiO 2 was prepared via a hydrothermal treatment and tested for the same reactions. All the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with energy dispersive X-ray (EDX) measurements, diffuse reflectance spectroscopy (DRS), Raman spectroscopy and Fourier transform …
Photocatalytic Processes in Membrane Reactors
2010
Conversion and degradation processes of various substrates in various types of matrices using both artificial and solar light are today very attractive by considering the scarcity and the expensiveness of the conventional energy sources. Coupling of membrane with light has shown to be very powerful and promising hybrid process, especially because a synergistic effect has been often observed. Some examples of reactions carried out to produce useful chemicals or to degrade noxious species in the framework of the green chemistry approach are reported. Fundamentals of heterogeneous photocatalysis, in general, and photocatalytic reactions in membrane reactors, in particular, are treated with a f…
Halogen Bonding beyond Crystals in Materials Science
2019
Halogen bonding has recently gained well deserved attention in present-day research for its importance in many fields of supramolecular science and crystal engineering. Although generally overlooked in comprehensive studies in the past, halogen bonding has become an important tool also in the field of materials science. An increased number of scientific reports are published every year where halogen bonding is exploited in soft materials rather than in crystal engineering. Here, we focus on a description of the most exciting contemporary developments in the field of halogen-bonded functional soft materials, assembled using the guiding principles of crystal engineering. We give a particular …
Azobenzene-based difunctional halogen-bond donor: Towards the engineering of photoresponsive co-crystals
2014
Halogen bonding is emerging as a powerful non-covalent interaction in the context of supramolecular photoresponsive materials design, particularly due to its high directionality. In order to obtain further insight into the solid-state features of halogen-bonded photoactive molecules, three halogen-bonded co-crystals containing an azobenzene-based difunctional halogen-bond donor molecule, (E)-bis(4-iodo-2,3,5,6-tetrafluorophenyl)diazene, C12F8I2N2, have been synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal structure of the non-iodinated homologue (E)-bis(2,3,5,6-tetrafluorophenyl)diazene, C12H2F8N2, is also reported. It is demonstrated that the stud…
Selective photocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxaldehyde by polymeric carbon nitride-hydrogen peroxide adduct
2018
Abstract Polymeric carbon nitride-hydrogen peroxide adduct (PCN-H2O2) has been prepared, thoroughly characterised and its application for selective photocatalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxaldehyde (FDC) in aqueous suspension has been studied. The PCN-H2O2 adduct is stable in aqueous suspension under UV and solar irradiation up to 100 °C. It is also stable up to 200 °C if heated in air, while at temperatures close to 300 °C its decomposition takes place. Based on the obtained characterisation data it has been proposed that H2O2 attaches to the non-polymerised carbon nitride species and to the heptazine nitrogen atoms, thus producing strong hydrogen bond…