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1. Size, nanostructure, and composition dependence of bimetallic Au-Pd supported on ceria-zirconia mixed oxide catalysts for selective oxidation of benzyl alcohol

Author

Olmos, Carol, Chinchilla, Lidia Esther, Villa, Alberto, Delgado, Juan José, Hungría, Ana Belén, Blanco, Ginesa, Prati, Laura, Calvino, José Juan, and Chen, Xiaowei

Subjects
Physics - Chemical Physics
Abstract

A bimetallic Au-Pd catalyst supported on ceriazirconia with Au:Pd molar ratio 0.8 has been synthesized using a simultaneous deposition-precipitation method and oxidized at 250, 450, and 700 $^\circ$C in order to modify its particle size, nanostructure, and composition. Combined Xray energy dispersive spectroscopy and Xray photoelectron spectroscopy analysis clearly evidence that the bimetallic Au-Pd catalyst oxidized at 250 $^\circ$C is made up of a mixture of monometallic Au and Pd and bimetallic Au-Pd nanoparticles with Au:Pd ratios varying over a wide range. Increasing oxidation temperature leads to a stronger interaction between Au and Pd. Meanwhile, a slight increase of particle size and a narrowing of the Au:Pd ratio in the bimetallic nanoparticles take place. Compared with titania and activated carbon supports, the resistance against sintering at high temperatures of Au-Pd metal particles supported on ceriazirconia is proven to be higher. A synergistic effect has been observed for selective oxidation of benzyl alcohol on these catalysts. The catalytic activity decreases only slightly after oxidation at 450 $^\circ$C. However, oxidation at 700 $^\circ$C results in much lower catalytic activity. Migration of Pd onto Au particles during oxidation of benzyl alcohol enhances the catalytic activity of a physical mixture of monometallic Au and Pd supported on ceriazirconia catalysts. This fact, jointly with an analysis of the intrinsic activity, reveals the influence of the actual nature of Au-Pd interactions in the bimetallic particles, which points to higher activity of Au@Pd or Au@Pd@Pd nanostructures on ceria-zirconia support., Comment: 12 pages, 8 figures

Published
2024
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3. Some results on discrete eigenvalues for the Stochastic Nonlinear Schroedinger Equation in fiber optics

Author

Prati, Laura and Barletti, Luigi

Subjects
Nonlinear Sciences - Pattern Formation and Solitons, Mathematical Physics
Abstract

We study a stochastic Nonlinear Schroedinger Equation (NLSE), with additive white Gaussian noise, by means of the Nonlinear Fourier Transform (NFT). In particular, we focus on the propagation of discrete eigenvalues along a focusing fiber. Since the stochastic NLSE is not exactly integrable by means of the NFT, then we use a perturbation approach, where we assume that the signal-to-noise ratio is high. The zeroth-order perturbation leads to the deterministic NLSE while the first-order perturbation allows to describe the statistics of the discrete eigenvalues. This is important to understand the properties of the channel for recently devised optical transmission techniques, where the information is encoded in the nonlinear Fourier spectrum.

Published
2020
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8. Cu and Fe modified Cerium and Zirconium Oxides for the Oxidation of Cyclohexane to KA Oil.

Author

Vomeri, Alessandro, Stucchi, Marta, Villa, Alberto, Hungría, Ana B., Calvino, José, and Prati, Laura

Subjects
ZIRCONIUM oxide, CERIUM oxides, COPPER, SURFACE chemistry, X-ray diffraction
Abstract

Ce and Zr oxides have been tested in the oxidation of cyclohexane to KA oil because of the possibility to tune their crystal structure and redox properties by introducing defects, and of modifying their mechanical and thermal stability. The redox properties of the two oxides, prepared by the inverse microemulsion technique, have been tuned by homogeneously including Cu or Fe (10 % molar) into their structures. These modifications led to very different behaviours in terms of both KA oil productivity and K/A ratios, especially upon undergoing reduction treatment, being the reduced Cu‐modified CeO2 oxide the most active catalyst, able to produce 2.2 mmol of KA oil after 5 hours with 93.2 % selectivity (K/A 2.6). The materials obtained have been characterized by solid state analytical techniques to study their structure, morphologies as well as their bulk and surface chemistry (STEM/EDX, BET, XRD, XPS). [ABSTRACT FROM AUTHOR]

Published
2024
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12. Combined Role of {001} Facet-Enriched Morphology and Gold Nanoparticle Deposition on Anatase TiO2Photoactivity

Author

Montalbano, Marco, Marra, Gianluigi, Longhi, Mariangela, Prati, Laura, Selli, Elena, and Dozzi, Maria Vittoria

Abstract

The interplay on anatase TiO2photoactivity between particle morphology and gold nanoparticles (NPs) deposition, via either deposition–precipitation (DP) or photodeposition (P), is here investigated by evaluating the photoactivity of Au modified anatase (Au/TiO2) nanocrystals with either a pseudospherical shape or a nanosheet structure in both reduction and oxidation test reactions. The presence of Au NPs on the anatase surface only slightly affects its photoactivity in Cr(VI) reduction, which is kinetically limited by the anodic half-reaction, whereas a larger exposure of highly oxidant {001} facets is beneficial for overcoming this rate-determining step. In the photocatalytic oxidation of both formic acid, proceeding through a direct mechanism, and rhodamine B (RhB) on surface fluorinated photocatalysts, occurring through a hydroxyl-radical-mediated mechanism, the presence of gold NPs produces a significant photoactivity increase only with spherically shaped photocatalysts, mainly exposing {101} facets. These results are rationalized in light of the preferential migration of photogenerated, oppositely charged carriers toward different crystal facets. In fact, when the Au/TiO2material mainly exposes the more oxidant {001} facets, where photoproduced holes preferentially migrate, recombination between these latter and the electrons captured by Au NPs is favored. Instead, Au NPs on {101} facets efficiently capture photopromoted electrons, preferentially migrating toward such facets with a consequent improvement of photoproduced charge separation.

Published
2024
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34. N-Doping Effect on the Activity of TiO2 Supported Catalysts in Glycerol Oxidation

Author

Cherni, Dhia, Moussa, Noomen, NCIB, Mohamed Faouzi, Prati, Laura, Villa, Alberto, Abdalla, Hassan, Series editor, Abdul Mannan, Md., Series editor, Alalouch, Chaham, Series editor, Attia, Sahar, Series editor, Boemi, Sofia Natalia, Series editor, Bougdah, Hocine, Series editor, Bozonnet, Emmanuel, Series editor, De Bonis, Luciano, Series editor, Hawkes, Dean, Series editor, Kostopoulou, Stella, Series editor, Mahgoub, Yasser, Series editor, Mesbah Elkaffas, Saleh, Series editor, Mohareb, Nabil, Series editor, O. Gawad, Iman, Series editor, Oostra, Mieke, Series editor, Pignatta, Gloria, Series editor, Pisello, Anna Laura, Series editor, Rosso, Federica, Series editor, Kallel, Amjad, editor, Ksibi, Mohamed, editor, Ben Dhia, Hamed, editor, and Khélifi, Nabil, editor

Published
2018
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48. The Effect of Sibunit Carbon Surface Modification with Diazonium Tosylate Salts of Pd and Pd-Au Catalysts on Furfural Hydrogenation

Author

German, Dmitrii, primary, Kolobova, Ekaterina, additional, Pakrieva, Ekaterina, additional, Carabineiro, Sónia A. C., additional, Sviridova, Elizaveta, additional, Perevezentsev, Sergey, additional, Alijani, Shahram, additional, Villa, Alberto, additional, Prati, Laura, additional, Postnikov, Pavel, additional, Bogdanchikova, Nina, additional, and Pestryakov, Alexey, additional

Published
2022
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