Cu and Pt clusters deposition on TiO2 powders by DC magnetron sputtering for photocatalytic hydrogen production

Titanium dioxide-based photocatalyst powders were obtained by deposition of copper and/or platinum clusters by means of pulsed direct current magnetron sputtering with different deposition times and plasma composition during Cu/Pt sputtering. A top-down configuration was employed with the sputtering source facing the powder holder mounted on a shaker mechanism, which continuously mixed the powder during the sputtering process. HRTEM analyses revealed the presence of well dispersed, subnanometric sized metal clusters, even for long deposition times, while XRPD analysis showed no modification of the TiO2crystal structure upon metal deposition. The so obtained powders were tested as photocatalysts in methanol photo-steam reforming for hydrogen production. The presence of Pt clusters increased the photoactivity with respect to that of bare TiO2. The plasma composition during Cu sputtering was found to strongly affect the photoactivity of the obtained materials, Cu alone deposited as co-catalyst in an Ar-only atmosphere imparting better photoactivity than Cu sputtered in Ar/O2. When the deposition of Cu clusters was coupled with the deposition of Pt clusters, an additive effect of the two metals in increasing TiO2photoactivity was observed if Cu clusters were sputtered in the absence of oxygen

Overview on the phenomenon of two-qubit entanglement revivals in classical environments

The occurrence of revivals of quantum entanglement between separated open quantum systems has been shown not only for dissipative non-Markovian quantum environments but also for classical environments in absence of back-action. While the phenomenon is well understood in the first case, the possibility to retrieve entanglement when the composite quantum system is subject to local classical noise has generated a debate regarding its interpretation. This dynamical property of open quantum systems assumes an important role in quantum information theory from both fundamental and practical perspectives. Hybrid quantum-classical systems are in fact promising candidates to investigate the interplay among quantum and classical features and to look for possible control strategies of a quantum system by means of a classical device. Here we present an overview on this topic, reporting the most recent theoretical and experimental results about the revivals of entanglement between two qubits locally interacting with classical environments. We also review and discuss the interpretations provided so far to explain this phenomenon, suggesting that they can be cast under a unified viewpoint.Comment: 16 pages, 9 figures. Chapter written for the upcoming book "Lectures on general quantum correlations and their applications

Metal Dispersion and Interaction with the Supports in the Coke Production Over Ethanol Steam Reforming Catalysts

reforming of ethanol. The catalytic performances, in terms of both H2 productivity and stability towards coking and sintering, were related to the physico-chemical properties of the catalysts. The samples were prepared either by synthesis of the support by precipitation and subsequent impregnation with the active phase, or by direct synthesis through Flame Pyrolysis. Many techniques have been used to assess the physico-chemical properties of both the fresh and spent catalysts. The samples showed different textural, structural and morphological properties, as well as different reducibility and thermal resistance, depending on the preparation method and support. The performance of the titania-supported catalysts were found very dependent on the preparation procedure, and we may conclude that operation at 625 C can be satisfactory from all the points of view of activity, productivity and C balance, allowing to limit the heat input to the reactor with respect to operation at 750 C

Effects of the TiO2 Phase in the Photocatalytic Oxidation of Aqueous NH3

Pure brookite, anatase and rutile TiO2 nanopowders, synthesized through thermo-hydrolysis of TiCl4 and modified by the deposition of Pt nanoparticles, were tested in the photocatalytic oxidation of aqueous NH3. Ammonia conversion and the selectivity toward mildly oxidized N2 and highly oxidized nitrite and nitrate anions were monitored during the runs, employing both naked and Pt-modified semiconductor particles as photocatalysts. Pt addition largely increased the rate of ammonia conversion. Pure brookite powders modified with Pt nanoparticles, which already proved to be efficient photocatalysts in thermodynamically up-hill H2 production through photo-steam reforming of methanol, were found to be most efficient also in down-hill aqueous ammonia abatement, with the highest selectivity (ca. 30 %) toward innocuous N2, this parameter being pretty important in view of a large scale photo-abatement of NH3, where the amount of noxious nitrite and nitrate ions must be kept as low as possible. Furthermore, intriguing effects concerning the mechanism of NH3 degradation where observed upon Pt nanoparticles deposition on pure brookite powders