Platinum

About: Platinum is a research topic. Over the lifetime, 49675 publications have been published within this topic receiving 1150035 citations. The topic is also known as: Pt & element 78.

Iridium As Catalyst and Cocatalyst for Oxygen Evolution/Reduction in Acidic Polymer Electrolyte Membrane Electrolyzers and Fuel Cells

Abstract: Among noble metal electrocatalysts, only iridium presents high activity for both the oxygen reduction reaction (ORR) in acid medium, in the oxide form, and the oxygen evolution reaction (OER) in acid medium, alloyed with first row transition metals. Indeed, platinum, the best catalyst for the ORR, has poor activity for the OER in any form, and ruthenium, the best catalyst for the OER, in the oxide form, possess poor activity for the ORR in any form. In this work, an overview of the application of Ir and Ir-containing catalysts for the OER in proton-exchange membrane water electrolyzer anodes, for the ORR in proton exchange membrane fuel cell cathodes, and for both OER and ORR in unit regenerative fuel cell oxygen electrodes is presented.

Synthesis and Characterization of the Nitrides of Platinum and Iridium

Abstract: Transition metal nitrides are of great technological and fundamental importance because of their strength and durability and because of their useful optical, electronic, and magnetic properties. We have evaluated a recently synthesized platinum nitride (PtN) that was shown to have a large bulk modulus, and we propose a structure that is isostructural with pyrite and has the stoichiometry PtN2. We have also synthesized a recoverable nitride of iridium under nearly the same conditions of pressure and temperature as PtN2. Although it has the same stoichiometry, it exhibits much lower structural symmetry. Preliminary results suggest that the bulk modulus of this material is also very large.

A Spectroscopic Study on the Nitrogen Electrochemical Reduction Reaction on Gold and Platinum Surfaces.

Abstract: The electrochemical reduction of nitrogen to ammonia on Au-based catalysts showed a reasonably high Coulombic efficiency. The pathway of this promising reaction, however, is not clear partially due to the lack of information on reaction intermediates. Herein, surface-enhanced infrared absorption spectroscopy (SEIRAS) was employed to study the reaction mechanisms of nitrogen reduction on an Au thin film for the first time. During the nitrogen reduction, the N2Hy species was detected with bands at 1453 (H-N-H bending), 1298 (-NH2 wagging), and 1109 cm-1 (N-N stretching) at potentials below 0 V against reversible hydrogen electrode. This result indicates that the nitrogen reduction reaction on Au surfaces follows an associative mechanism, and the N≡N bond in N2 tends to break simultaneously with the hydrogen addition. By comparison, no absorption band associated with N was observed on Pt surfaces under the same reaction condition. This result is consistent with the low efficiency of nitrogen reduction on Pt due to the much faster kinetics of hydrogen evolution reaction.

Kinetically Controlled Growth and Shape Formation Mechanism of Platinum Nanoparticles

Abstract: Recently, we have been able to synthesize platinum colloidal nanoparticles of different shapes (Science, 1996, 272, 1924). In this report, we present transmission electron microscopic (TEM) results on the time-dependent shape distribution of platinum nanoparticles during the growth period and its dependence on the concentration of the capping polymer as well as the pH of the solution. The results suggest a shape-controlled growth mechanism in which the difference between the rate of the catalytic reduction process of Pt2+ on the {111} and {100} faces, the competition between the Pt2+ reduction and the capping process on the different nanoparticle surfaces, and the concentration-dependent buffer action of the polymer itself all control the final distribution of the different shapes observed.

Catalytic oxidation of carbon monoxide on monodispersed platinum clusters: Each atom counts

Abstract: Nanoclusters open fascinating opportunities for quantum engineering because quantum-size effects become dominant in determining catalytic,1-3 optical,4 electronic,5 and magnetic6 properties. We succeeded in the controlled production of low-energy and high-flux monodispersed cluster beams, which allow for a systematic study of their reactivity after deposition onto a chemically inert substrate. We investigated the catalytic reaction that is the oxidation of CO on platinum and observed a distinct atom by atom size dependency for monodispersed platinum clusters on thin MgO(100) films. These results clearly show that the efficiency of a heterogeneous catalytic reaction can be tuned by the judicious choice of particle size.