Combined TPRx, in situ GISAXS and GIXAS studies of model semiconductor-supported platinum catalysts in the hydrogenation of ethene

Abstract

The preparation, characterization and catalytic reactivity of a GaN supported Pt catalyst in the hydrogenation of ethene are presented in this feature article, highlighting the use of in situ characterization of the material properties during sample handling and catalysis by combining temperature programmed reaction with in situ grazing incidence small-angle X-ray scattering and X-ray absorption spectroscopy. The catalysts are found to be sintering resistant at elevated temperatures as well as during reduction and hydrogenation reactions. In contrast to Pt particles of approximately 7 nm diameter, smaller particles of 1.8 nm in size are found to dynamically adapt their shape and oxidation state to the changes in the reaction environment. These smaller Pt particles also showed an initial deactivation in ethene hydrogenation, which is paralleled by the change in the particle shape. The subtle temperature-dependent X-ray absorbance of the 1.8 nm sized Pt particles indicates that subtle variations in the electronic structure induced by the state of reduction by electron tunnelling over the Schottky barrier between the Pt particles and the GaN support can be monitored.

Low‐temperature catalytic activity of CO oxidation by uni‐size Pt30 cluster disks bonded to silicon substrate

“…Indeed, in these decades, vigorous research studies have been made on catalytic actions driven by supported metal clusters . It has been shown that catalytic activities of gold clusters supported on the (100) surface of a MgO thin film prepared on a metal surface relate closely to their charge state; a three‐dimensional Au 8 placed an oxygen‐vacancy defect (F centre) of the MgO film reveals a high catalytic activity in the CO oxidation induced by charging due to the electron transfer from the F centre to the Au 8 , while that attached on a defect‐free MgO film has no catalytic activity because of less charging .…”

Tunable Oxygen Activation for Catalytic Organic Oxidation: Schottky Junction versus Plasmonic Effects

“…This strategy is intuitively straightforward, and its feasibility has been exhibited in hydrogenation reactions. In hydrogenation reactions, H 2 activation can be maneuvered through variations in the electronic structure of metal catalysts supported on semiconductors 12. Nevertheless, the carrier dynamics in the M–S junction are so complicated that the O 2 ‐activation efficacy of this design cannot be warranted.…”

Charge Transfer across the GaN/Pt Nanoparticle Interface in an Electrolyte

“…Shape-selective, monodisperse Pt nanoparticles (diameter: 8.1 nm) were prepared according to the polyol process [23,24] and deposited onto the GaN surfaces through spin-coating, thereby resulting in highly reproducible, homogeneous, and stable areal nanoparticle distributions without agglomeration. [11,12] Although this method does not create ordered arrays of nanoparticles, it is suitable for the preparation of low-coverage model catalyst systems to study nanoparticle-support interactions. [14] The total amount of Pt cuboctahedra on the surface was assessed from the nanoparticle diameter (by using TEM) and from the areal density of the nanoparticles (by using AFM).…”

“…[9,10] Although its wide bandgap (3.4 eV) severely limits its maximum efficiency under solar illumination, GaN constitutes a model system for the study of semiconductor/electrolyte interfaces and photocatalysis. [11][12][13][14][15] Electrochemical and photocatalytic applications require a fundamental understanding and, eventually, control of interfacial charge-transfer processes, as well as long-term electrode stability. The chemical control of interfacial charge-transfer kinetics is commonly achieved by either the addition of suitable redox agents to the electrolyte or by the deposition of thin metal overlayers onto the electrode.…”