Noble metal

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

Competitive CO and CO2 methanation over supported noble metal catalysts in high throughput scanning mass spectrometer

Abstract: High-throughput synthesis and screening methods have been developed for the heterogeneously catalyzed gas phase hydrogenation of CO and CO 2 (‘methanation’) over zirconia and ceria supported noble and base metal catalysts at 300–400 °C and ambient pressure. The discovery libraries, for primary screening, consisted of 11 × 11 arrays of 111 catalysts on 3 in. quartz wafers, and 16 × 16 arrays of 256 catalysts on 4 in. quartz wafers. Catalysts were prepared by liquid dispensing techniques and screened for catalytic activity in scanning mass spectrometers (SMS). This primary screening tool uses quadrupole mass spectrometry for rapid serial detection. More than 500 potential catalysts could be screened in a single day. A kinetic model based on fast equilibration by the reverse water–gas-shift reaction in parallel with about an order of magnitude slower CO hydrogenation is in good agreement with CO x conversion data. CO 2 is mainly reverse shifted to CO. Ru, Rh, and Ni were found to promote methanation whereas Pt tends to catalyze the reverse WGS reaction. Methanation activity can be enhanced by some acidic and redox dopants or suppressed by basic dopants. High conversions were achieved in SMS demonstrating the minimal scalability risk for short contact time reactions.

Glucose-oxidase like catalytic mechanism of noble metal nanozymes.

Abstract: Au nanoparticles (NPs) have been found to be excellent glucose oxidase mimics, while the catalytic processes have rarely been studied. Here, we reveal that the process of glucose oxidation catalyzed by Au NPs is as the same as that of natural glucose oxidase, namely, a two-step reaction including the dehydrogenation of glucose and the subsequent reduction of O2 to H2O2 by two electrons. Pt, Pd, Ru, Rh, and Ir NPs can also catalyze the dehydrogenation of glucose, except that O2 is preferably reduced to H2O. By the electron transfer feature of noble metal NPs, we overcame the limitation that H2O2 must be produced in the traditional two-step glucose assay and realize the rapid colorimetric detections of glucose. Inspired by the electron transport pathway in the catalytic process of natural enzymes, noble metal NPs have also been found to mimic various enzymatic electron transfer reactions including cytochrome c, coenzymes as well as nitrobenzene reductions. Gold nanoparticles (Au NPs) with enzyme-like activities are useful glucose oxidase mimics, but the insights into the mechanism of this reaction are limited. Here, the authors show that the process of glucose oxidation by Au NPs is analogous to the one catalysed by glucose oxidase, involving dehydrogenation and oxygen reduction to H2O2; and that other noble metal NPs also catalyse glucose dehydrogenation, but oxygen is preferably reduced to water.

Selective Hydrogenation of Crotonaldehyde to Crotyl Alcohol over Metal Oxide Modified Ir Catalysts and Mechanistic Insight

Abstract: The scope of metal oxide modified noble metal (M+M′Ox) catalysts was scrutinized in the hydrogenation of crotonaldehyde to crotyl alcohol as a model reaction under mild reaction conditions (303 K, 0.8 MPa, water solvent), demonstrating that MoOx, WOx, NbOx, FeOx and ReOx are effective metal oxides for Ir/SiO2 to enhance both the activity and selectivity, although the optimized (metal oxide)/(Ir metal) molar ratio depends on the metal oxide. MoOx modified Ir/SiO2 catalyst (Ir-MoOx/SiO2 (Mo/Ir = 1)) was the most efficient, providing a high yield of crotyl alcohol (90%) and a high TOF (217 h–1). The catalytic activity under such mild reaction conditions is the highest among the reported heterogeneous catalysts. These results showed that modification of active metals with an appropriate amount of metal oxides is an effective method for the development of efficient catalysts for selective hydrogenations. The reaction mechanism over the metal oxide modified Ir catalysts was investigated using Ir-ReOx/SiO2 (Re/I...