Noble metal

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

Superb Alkaline Hydrogen Evolution and Simultaneous Electricity Generation by Pt‐Decorated Ni3N Nanosheets

Abstract: The development of efficient hydrogen evolution reaction electrocatalysts is critical to the realization of clean hydrogen fuel production, while the sluggish kinetics of the Volmer-step substantially restricts the catalyst performances in alkali electrolyzers, even for noble metal catalysts such as Pt. Here, a Pt-decorated Ni3N nanosheet electrocatalyst is developed to achieve a top performance of hydrogen evolution in alkaline conditions. Possessing a high metallic conductivity and an atomic-thin semiconducting hydroxide surface, the Ni3N nanosheets serve as not only an efficient electron pathway without the hindrance of Schottky barriers, but also provide abundant active sites for water dissociation and generation of hydrogen intermediates, which are further adsorbed on the Pt surface to recombine to H2. The Pt-decorated Ni3N nanosheet catalyst exhibits a hydrogen evolution current density of 200 mA cm−2 at an overpotential of 160 mV versus reversible hydrogen electrode, a Tafel slope of ≈36.5 mV dec−1, and excellent stability of 82.5% current retention after 24 h of operation. Moreover, a hybrid cell consisting of a Pt-decorated Ni3N nanosheet cathode and a Li-metal anode is assembled to achieve simultaneous hydrogen evolution and electricity generation, exhibiting >60 h long-term hydrogen evolution reaction stability and an output voltage ranging from 1.3 to 2.2 V.

Role and Function of Noble-Metal/Cr-Layer Core/Shell Structure Cocatalysts for Photocatalytic Overall Water Splitting Studied by Model Electrodes

Abstract: The mechanism of hydrogen evolution by a core/shell noble-metal/Cr2O3 particulate as a highly efficient cocatalyst for overall water splitting under visible light using the photocatalyst (Ga1−xZnx)(N1−xOx) is investigated by electrochemical and in situ spectroscopic measurements of model electrodes. The electrodes are prepared by electrochemical deposition of 1.8−3.5 nm thick Cr2O3 films on Rh and Pt plates and are evaluated as model systems of Rh/Cr2O3 and Pt/Cr2O3 core/shell particulates, which have previously been applied effectively as cocatalysts for hydrogen evolution in this system. Proton adsorption/desorption and H2 evolution currents are observed for both the Cr2O3-coated and the bare electrodes, and the infrared absorption band due to Pt−H stretching (2039 cm−1) is apparent for both the coated and the bare electrodes. These observations indicate that the Cr2O3 layer does not interfere with proton reduction or hydrogen evolution and that proton reduction takes place at the Cr2O3/Pt interface. Ho...

Oxidation of CO, ethanol and toluene over TiO2 supported noble metal catalysts

Abstract: The oxidation of CO, ethanol and toluene was investigated on noble metal catalysts (Pt, Pd, Ir, Rh and Au) supported on TiO 2 . The catalysts were prepared by liquid phase reduction deposition (LPRD) and by incipient wetness impregnation (IMP). It was observed that the preparation method can have a significant effect on the dispersion of the metallic phase, and subsequently on the performance of the catalysts towards total oxidation of CO or VOC. For CO oxidation, Au IMP was the worst catalyst, while Au LPRD was the most active. This can be explained in terms of different Au particle sizes, well known to be related with catalytic activity. For all the other metals, LPRD also produces better results, although the differences are not so marked as with gold. Iridium seems to be the only exception since results were very similar. In VOC oxidation, the following performance trend was observed: Pt/TiO 2 > Pd/TiO 2 ≫ Rh/TiO 2 ≈ Ir/TiO 2 ≫ Au/TiO 2 , for both preparation methods. Ethanol and toluene oxidation over Pt and Pd catalysts were found to be structure sensitive reactions. Some experiments with ethanol/toluene mixtures were performed using the best catalyst (Pt/TiO 2 ). It was observed that toluene inhibits the combustion of ethanol, namely by slowing down the partial oxidation of ethanol towards acetaldehyde. Ethanol also has a slight inhibition effect on the total oxidation of toluene.

Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst.

Abstract: Producing hydrogen through solar water splitting requires the coverage of large land areas. Abundant metal-based molecular catalysts offer scalability, but only if they match noble metal activities. We report on a highly active p-GaInP2 photocathode protected through a 35-nm TiO2 layer functionalized by a cobaloxime molecular catalyst (GaInP2–TiO2–cobaloxime). This photoelectrode mediates H2 production with a current density of ∼9 mA cm−2 at a potential of 0 V versus RHE under 1-sun illumination at pH 13. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9 s−1. Bare GaInP2 shows a rapid current decay, whereas the GaInP2–TiO2–cobaloxime electrode shows ≤5% loss over 20 min, comparable to a GaInP2–TiO2–Pt catalyst particle-modified interface. The activity and corrosion resistance of the GaInP2–TiO2–cobaloxime photocathode in basic solution is made possible by an atomic layer-deposited TiO2 and an attached cobaloxime catalyst. Producing hydrogen via solar water splitting with metal-based molecular catalysts offers scalability. An active p-GaInP2 photocathode stabilized by a TiO2 layer functionalized by a cobaloxime molecular catalyst is now reported for water reduction.