Noble metal

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

Studying the chemical, optical and catalytic properties of noble metal (Pt, Pd, Ag, Au)–Cu2O core–shell nanostructures grown via a general approach

Abstract: We studied the chemical, optical and catalytic properties of metal (Pt, Pd, Ag, Au)–Cu2O core–shell nanoparticles grown via a simple and reproducible approach which utilizes aqueous-phase reactions at room temperature. We were able to control the thickness of the Cu2O shell and examine the effect of the core's shape and size on the structure and properties of the hybrid nanocrystals. We also studied the optical properties of the hybrid nanocrystals, in particular the effect of the Cu2O shell thickness on the frequency of the plasmon of gold nanorods. In addition, the catalytic activity of the hybrid nanostructures was examined by testing the reduction reaction of 4-nitrophenol with NaBH4. Finally, the hybrid metal–Cu2O nanostructures were used as templates to form the yolk–shell of metal–Cu2S materials. The interface and the crystalline structures of the four hybrid nanostructures were extensively characterized by high resolution transmission electron microscopy (HRTEM), energy-filtered TEM (EFTRM) and X-ray diffraction (XRD).

Catalytic wet oxidation of p-chlorophenol over supported noble metal catalysts

Abstract: Heterogeneous catalytic wet oxidation of aqueous p-chlorophenol (p-CP) solution was investigated at 453 K and 2.6 MPa in a slurry reactor. The performance of noble metal catalysts was compared with that of traditional manganese catalysts. Activated carbon supported catalysts showed significant higher activities for total organic carbon (TOC) reduction than those supported on alumina or cerium oxide. Pt was found to be the most active metal for p-chlorophenol oxidation. The activities of noble metal catalysts were found to correlate with heat of formation of metal oxides. CO2 is the predominant oxidation product with formation of minor p-benzoquinone and acetic acid as intermediate compounds. Possible reaction pathway was also discussed.

Photocatalytic properties of TiO2 modified with gold nanoparticles in the degradation of oxalic acid in aqueous solution

Abstract: The commercially available TiO 2 -catalyst (Degussa P25) was supported by spray pyrolysis deposition method on the outer surface of the quartz tubes, incorporated in photocatalytic reactor. The crystal structure and the morphology of the films were studied. The immobilized TiO 2 is modified with nanosized gold particles by the photoreduction method to obtain different noble metal loading (0.05–0.4 wt.%). The characterization of the synthesized catalysts was carried out by the BET method, X-ray photoelectron spectroscopy (XPS), SEM, TEM and the adsorption of the model pollutant was determined. The degradation of oxalic acid has been studied in aqueous solution photocatalyzed by band-gap-irradiated TiO 2 , modified with nanosized gold particles. The presence of low amounts of gold on the TiO 2 surface leads to an increase of its photocatalytic activity. The maximum value of the photocatalytic activity was registered with the ≈0.16 wt.% Au on TiO 2 sample. At this concentration the activity of the Au-modified TiO 2 is approximately double that of the semiconducting support. The adsorption properties of the catalysts, as well as the noble metal content on the surface of the support, influence the efficiency of the photocatalytic process. The reaction rate of photocatalytic degradation of the oxalic acid follows a zero kinetic order according to the Langmuir–Hinshelwood model.

Noble metal-free MoS2 modified Mn0.25Cd0.75S for highly efficient visible-light driven photocatalytic H2 evolution

Abstract: Development of noble metal-free and highly efficient co-catalyst that endows semiconductor materials with high performance is of great significance towards enhancing photocatalytic H2 evolution. Herein, a series of novel Mn0.25Cd0.75S/MoS2 composites have been successfully prepared by a facile one-step hydrothermal method. The photocatalytic activity of the as-prepared photocatalysts for H2 production from water splitting under visible-light irradiation (λ ≥ 400 nm) was investigated. The results showed that Mn0.25Cd0.75S/MoS2 heterostructured composites have a higher photocatalytic activity than Mn0.25Cd0.75S, implying that the intimate interfacial contact between Mn0.25Cd0.75S and MoS2 facilitates electron transfer from Mn0.25Cd0.75S to MoS2, thus promoting the separation of photogenerated charge carriers and providing more active sites for H2 evolution reaction. The introduction of noble metal-free MoS2 co-catalyst led to a remarkable improvement in the photocatalytic H2 evolution activity of Mn0.25Cd0.75S, and the content of MoS2 in composite had an important influence on the photocatalytic activity. It was confirmed that 0.7 wt% of MoS2 loading content achieves a maximum photocatalytic H2 evolution rate of 12.47 mmol g−1 h−1, which was much higher than that of Mn0.25Cd0.75S and also slightly higher than that of Mn0.25Cd0.75S/Pt (1.0 wt%). This work revealed that low cost MoS2 could replace noble metal Pt as a highly efficient co-catalyst in enhancing the photocatalytic activity of semiconductor materials.