Noble metal

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

Direct, Electrocatalytic Oxygen Reduction by Laccase on Anthracene-2-methanethiol-Modified Gold

Abstract: Laccase, a multicopper oxidase, catalyzes the four-electron reduction of oxygen to water. Upon adsorption to an electrode surface, laccase is known to reduce oxygen at overpotentials lower than the best noble metal electrocatalysts usually employed. Whereas the electrocatalytic activity of laccase is well established on carbon electrodes, laccase does not typically adsorb to better defined noble metal surfaces in an orientation that allows for efficient electrocatalysis. In this work, we utilized anthracene-2-methanethiol (AMT) to modify the surface of Au electrodes and examined the electrocatalytic activity of adsorbed laccase. AMT facilitated the adsorption of laccase, and the onset of electrocatalytic oxygen reduction was observed as high as 1.13VRHE. We observed linear Tafel behavior with a 144 mV/dec slope, consistent with an outer sphere single electron transfer from the electrode to a Cu site in the enzyme as the rate-determining step of the oxygen reduction mechanism.

Nitrogen-doped graphene stabilized gold nanoparticles for aerobic selective oxidation of benzylic alcohols

Abstract: Increasing efforts have been made to fabricate Au/graphene composites due to the fascinating properties of both graphene and gold. Some Au nanoparticles with an average size of tens of nanometers were directly deposited on reduced graphene oxide (RGO), utilizing the residual oxy-functional groups as the “hitching post” of the nanoparticles. Some functional groups, such as amino and thiol, were attached to the surface of the graphene in order to stabilize gold nanoparticles with a smaller particle size (<5 nm in general). Unfortunately, most of these strategies result in Au particles with limited exposed atoms, which is certainly a disadvantage for their application, such as catalysis. Introduction of nitrogen heteroatoms into the framework of graphene can not only modulate the electronic structure, but also change the surface properties of the graphene. In this work, naked Au nanoparticles with an average size of about 2–4 nm were fabricated on nitrogen-doped graphene nanosheets (NG) via the direct simple reduction method. The Au/NG nanocomposites were characterized by XRD, XPS, TEM, AFM and Raman. It was revealed that the nitrogen atoms doped in NG, rather than defects or oxygen moieties, play an essential role in stabilizing Au NPs. It was also found that the initial reaction rate of benzyl alcohol oxidation over the Au/NG catalyst is about ten fold higher than that over Au/graphene catalysts. Our findings may provide a clue of nitrogen incorporation to stabilize uncapped noble metal nanoparticles on graphene or other inorganic oxide supports, such as TiO2.

Green synthesis of Pt-doped TiO2 nanocrystals with exposed (001) facets and mesoscopic void space for photo-splitting of water under solar irradiation.

Abstract: We report a non-trivial facile chemical approach using ionic liquid ([bmim][Cl]) as a porogen for the synthesis of (001) faceted TiO2 nanocrystals having mesoscopic void space. This faceted TiO2 nanomaterial has been doped with Pt nanoclusters through chemical impregnation. The resulting Pt-doped TiO2 nanomaterials are thoroughly characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), ultra high resolution transmission electron microscopy (UHR-TEM), energy dispersive X-ray spectrometry (EDX), UV-vis diffuse reflection spectroscopy (DRS) and N2 sorption studies. These Pt/TiO2 nanocrystals with (001) exposed facets are employed as efficient and benign catalysts for hydrogen production from pure water and methanol–water systems under one AM 1.5G sunlight illumination. The effect of platinum loading and methanol–water ratio on the photocatalytic activity of the faceted TiO2 nanocrystals are investigated and it is found that hydrogen evolution rates have been enhanced significantly upon Pt loading. Under optimized reaction conditions the highest photocatalytic activity of 11.2 mmol h−1 g−1 has been achieved over ca. 1.0 wt% Pt loaded Pt/TiO2 nanocrystals with (001) exposed facets, which is one of the highest hydrogen evolution rates over the noble metal/TiO2 system reported to date in the literature.

Ultrafine Rh nanocrystals decorated ultrathin NiO nanosheets for urea electro-oxidation

Abstract: Heterostructured noble metal/transition metal nanohybrids have attracted increasing attention in energy/environment-related electrocatalysis field due to their high activity. In this work, the ultrathin NiO nanosheets (NiO-NSs) decorated with ultrafine Rh nanocrystals (Rh-NCs) electrocatalyst (termed as Rh-NCs/NiO-NSs) is successfully synthesized by using mixed-cyanogels-NaBH4 method and succedent heat treatment. Physical characterizations confirm that as-prepared Rh-NCs/NiO-NSs have 1.6 nm thickness and a large specific surface area of 166.2 m2 g−1, and ultrafine Rh-NCs are uniformly dispersed on surface of NiO-NSs. Electrochemical measurements show that the incorporation of Rh-NCs can promote the generation of NiIIIOOH species and accelerate the oxidation of CO, thus significantly improving the electrocatalytic performance of NiO-NSs for urea electro-oxidation reaction (UEOR). The UEOR current at Rh-NCs/NiO-NSs achieves the 616 mA mg−1 at 1.55 V potential, which is 11.5 times bigger than that at NiO-NSs in 1 M KOH solution with 0.33 M urea. Additionally, Rh-NCs/NiO-NSs also show excellent long-term stability due to improved structural/chemical stability and anti-poisoning capability.

Noble metal nanoclusters and nanoparticles precede mineral formation in magmatic sulphide melts

Abstract: In low temperature aqueous solutions, it has long been recognized by in situ experiments that many minerals are preceded by crystalline nanometre-sized particles and non-crystalline nanophases. For magmatic systems, nanometre-sized precursors have not yet been demonstrated to exist, although the suggestion has been around for some time. Here we demonstrate by high temperature quench experiments that platinum and arsenic self-organize to nanoparticles, well before the melt has reached a Pt-As concentration at which discrete Pt arsenide minerals become stable phases. If all highly siderophile elements associate to nanophases in undersaturated melts, the distribution of the noble metals between silicate, sulphide and metal melts will be controlled by the surface properties of nano-associations, more so than by the chemical properties of the elements.