2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 8: Surfaces and Interfaces(SISAM), Composite, Ceramic and Nanomaterials
| Editors: | Kongoli F, Braems I, Demange V, Dubois JM, Pech-Canul M, Patino CL, Fumio O |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 249 pages |
| ISBN: | 978-1-987820-75-1 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
CD shopping page
Light to Hydrogen Processes and Relative Phenomena in the Transition Metal Oxides and Silver and Cuprous Halides
Alexander Gavrilyuk1;1IOFFE PHYSICAL TECHNICAL INSTITUTE OF THE RUSSIAN ACADEMY OF SCIENCES, Saint-Petersburg, Russian Federation;
Type of Paper: Regular
Id Paper: 224
Topic: 42
Abstract:
WO3, MoO3, and V2O5 are famous “hydrogenphilics” capable of accommodating of great quantities of hydrogen atoms, which yields dramatic changing of the optical parameters. Photoinjection of atomic hydrogen was carried out into the oxide films; hydrogen being split off from adsorbed hydrogen-containing molecules (hydrogen donors) previously adsorbed on the oxide surface via a photochemical reaction. Being an excellent reducing agent, often a latent agent, and playing the role of a dopant or a catalyst, sometimes, combining both functions, atomic hydrogen triggers various processes on the solid surface. The adsorption mechanism for specially selected organic molecules (hydrogen donors) has been described. The great catalytic effect for the photochemical reaction of abstraction of hydrogen atoms from the adsorbed organic molecules has been achieved due to formation of donor-acceptor and hydrogen bonds, which perturbs both electronic and ionic systems of the molecules. The experiments, carried out in the wide temperature range, made it possible to consider the reaction mechanism as the proton-coupled electron transfer (PCET) between the adsorbed molecule and the oxide surface. A non-zero low temperature reaction rate limit was discovered, which is a reliable evidence for a tunneling mechanism reaction. The changes in the oxide optical properties in the wide spectral range upon insertion of hydrogen atoms have been considered. Special attention has been paid to formation of different color centers: bulk and surface (paramagnetic and diamagnetic). The nature of the giant shift of the fundamental absorption edge in the V2O5 nanocrystalline has been discussed. The function of the photochemical hydrogen as a catalyst for surface chemical reaction, yielding formation of other nanostructures, has been investigated. Several examples of hydrogen photosensitization carried out simultaneous to illumination in silver and cuprous halides are presented. The performances of the nano-heterostructures employing hydrogen photo-initiated spillover are discussed. The function of the photochemical hydrogen as a catalyst for secondary surface photochemical reactions has been shown. Several examples of hydrogen photosensitization carried out simultaneous to illumination in silver and cuprous halides have been observed in the double-layer structures: AgCl-WO3, AgI-WO3, RbAg4I5-WO3, and CuCl-WO3. First, the direct PIH into the WO3 films has been carried out, and then the detached hydrogen atoms migrating into the halide layer provided formation of sensitization centers, which enhanced the photolysis of the halides. The currently proceeding investigations have been showed the perceptiveness of the multifunctional materials on the base of the transition metal oxides either for fundamental or applied research.