Noble metal

About: Noble metal is a research topic. Over the lifetime, 15113 publications have been published within this topic receiving 337947 citations.

A family of metal-organic frameworks exhibiting size-selective catalysis with encapsulated noble-metal nanoparticles.

Abstract: The encapsulation of noble-metal nanoparticles (NPs) in metal-organic frameworks (MOFs) with carboxylic acid ligands, the most extensive branch of the MOF family, gives NP/MOF composites that exhibit excellent shape-selective catalytic performance in olefin hydrogenation, aqueous reaction in the reduction of 4-nitrophenol, and faster molecular diffusion in CO oxidation. The strategy of using functionalized cavities of MOFs as hosts for different metal NPs looks promising for the development of high-performance heterogeneous catalysts.

Efficient photoelectrochemical hydrogen generation using heterostructures of Si and chemically exfoliated metallic MoS2.

Abstract: We report the preparation and characterization of highly efficient and robust photocathodes based on heterostructures of chemically exfoliated metallic 1T-MoS2 and planar p-type Si for solar-driven hydrogen production. Photocurrents up to 17.6 mA/cm(2) at 0 V vs reversible hydrogen electrode were achieved under simulated 1 sun irradiation, and excellent stability was demonstrated over long-term operation. Electrochemical impedance spectroscopy revealed low charge-transfer resistances at the semiconductor/catalyst and catalyst/electrolyte interfaces, and surface photoresponse measurements also demonstrated slow carrier recombination dynamics and consequently efficient charge carrier separation, providing further evidence for the superior performance. Our results suggest that chemically exfoliated 1T-MoS2/Si heterostructures are promising earth-abundant alternatives to photocathodes based on noble metal catalysts for solar-driven hydrogen production.

Nitrogen-Doped Graphene Nanosheets as Metal-Free Catalysts for Aerobic Selective Oxidation of Benzylic Alcohols

Abstract: This work demonstrates the molecular engineering of active sites on a graphene scaffold. It was found that the N-doped graphene nanosheets prepared by a high-temperature nitridation procedure represent a novel chemical function of efficiently catalyzing aerobic alcohol oxidation. Among three types of nitrogen species doped into the graphene lattice—pyridinic N, pyrrolic N, and graphitic N—the graphitic sp2 N species were established to be catalytically active centers for the aerobic oxidation reaction based on good linear correlation with the activity results. Kinetic analysis showed that the N-doped graphene-catalyzed aerobic alcohol oxidation proceeds via a Langmuir–Hinshelwood pathway and has moderate activation energy (56.1 ± 3.5 kJ·mol–1 for the benzyl alcohol oxidation) close to that (51.4 kJ·mol–1) proceeding on the catalyst Ru/Al2O3 reported in literature. An adduct mechanism was proposed to be different remarkably from that occurring on the noble metal catalyst. The possible formation of a sp2 N–...

Corrosion micromorphology of noble metal alloys and depletion gilding

Abstract: Noble metal alloys commonly undergo selective dissolution during anodic corrosion whereby the less noble component is dissolved preferentially. This is particularly interesting, as it leads to a depletion of the less noble species not only at the surface of the metal but also at an appreciable depth within it, implying that a mass transport of atoms is occurring either through the bulk of the crystal lattice or across the surface to support the continuing dissolution. Experiments in which the micromorphology of silver–gold alloys is observed during such corrosive treatment have shown that surface diffusion of gold plays an important part in this process. As surface silver atoms are dissolved the residual gold atoms reform into gold-rich islands so that fresh silver atoms are continuously exposed to the environment layer by layer. These observations will be described in detail elsewhere1. Here the mechanism of surface re-arrangement is considered, which leads to the accumulation of gold-rich surface regions, and throws a new light on the ancient craft of depletion gilding.