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Rh Nanoparticles (rh + nanoparticle)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Preparation of Core,Shell-Structured Nanoparticles (with a Noble-Metal or Metal Oxide Core and a Chromia Shell) and Their Application in Water Splitting by Means of Visible Light

CHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2010
Kazuhiko Maeda Dr.
Abstract Core,shell-structured nanoparticles, consisting of a noble metal or metal oxide core and a chromia (Cr2O3) shell, were studied as promoters for photocatalytic water splitting under visible light. Core nanoparticles were loaded by impregnation, adsorption or photodeposition onto a solid solution of gallium nitride and zinc oxide (abbreviated GaN:ZnO), which is a particulate semiconductor photocatalyst with a band gap of approximately 2.7,eV, and a Cr2O3 shell was formed by photodeposition using a K2CrO4 precursor. Photodeposition of Cr2O3 on GaN:ZnO modified with a noble metal (Rh, Pd and Pt) or metal oxide (NiOx, RuO2 and Rh2O3) co-catalyst resulted in enhanced photocatalytic activity for overall water splitting under visible light (,>400,nm). This enhancement in activity was primarily due to the suppression of undesirable reverse reactions (H2,O2 recombination and/or O2 photoreduction) and/or protection of the core component from chemical corrosion, depending on the core type. Among the core materials examined, Rh species exhibited relatively high performance for this application. The activity for visible-light water splitting on GaN:ZnO modified with an Rh/Cr2O3 core,shell configuration was dependent on both the dispersion of Rh nanoparticles and the valence state. In addition, the morphology of the Cr2O3 photodeposits was significantly affected by the valence state of Rh and the pH at which the photoreduction of K2CrO4 was conducted. When a sufficient amount of K2CrO4 was used as the precursor and the solution pH ranged from 3 to 7.5, Cr2O3 was successfully formed with a constant shell thickness (,2,nm) on metallic Rh nanoparticles, which resulted in an effective promoter for overall water splitting. [source]

Carbohydrate-Derived 1,3-Diphosphite Ligands as Chiral Nanoparticle Stabilizers: Promising Catalytic Systems for Asymmetric Hydrogenation

CHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 8 2009
Aitor Gual Dr.
Abstract Metallic Ru, Rh, and Ir nanoparticles were prepared by the decomposition of organometallic precursors under H2 pressure in the presence of 1,3-diphosphite ligands, derived from carbohydrates, as stabilizing agents. Structural modifications to the diphosphite backbone were found to influence the nanoparticles, size, dispersion, and catalytic activity. In the hydrogenation of o - and m -methylanisole, the Rh nanoparticles showed higher catalytic activity than the corresponding Ru nanoparticles. The Ir nanoparticles presented the lowest catalytic activity of the series. In all cases, the hydrogenation of o -methylanisole gave total selectivity for the cis -product, however, the ee of the product was always less than 6,%. A maximum of 81,% cis -selectivity was obtained for the hydrogenation of m -methylanisole, however, no asymmetric induction was observed. These results show that the catalytic activity is affected by a combination of influences from the substrate, the diphosphite ligands, and the metallic nanoparticles. [source]

Catalytic porous ceramic prepared in-situ by sol-gelation for butane-to-syngas processing in microreactors

AICHE JOURNAL, Issue 7 2009
Nico Hotz
Abstract In this study, a novel flow-based method is presented to place catalytic nanoparticles into a reactor by sol-gelation of a porous ceramic consisting of Rh/ceria/zirconia nanoparticles, silica sand, ceramic binder, and a gelation agent. This method allows for the placement of a liquid precursor containing the catalyst into the final reactor geometry without the need of impregnating or coating of a substrate with the catalytic material. The so generated foam-like porous ceramic shows properties highly appropriate for use as catalytic reactor material, e.g., reasonable pressure drop due to its porosity, high thermal and catalytic stability, and excellent catalytic behavior. To investigate the catalytic activity, microreactors containing this foam-like ceramic are employed for the production of hydrogen and carbon monoxide-rich syngas from butane. The effect of operating parameters such as the inlet flow rate on the hydrocarbon processing is analyzed and the limitation of the reactor by diffusion mass transport is investigated. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]