Title
The role of hydrogen during Pt-Ga nanocatalyst formationThe role of hydrogen during Pt-Ga nanocatalyst formation
Author
Faculty/Department
Faculty of Sciences. Physics
Research group
Electron microscopy for materials research (EMAT)
Publication type
article
Publication
Cambridge,
Subject
Physics
Chemistry
Source (journal)
Physical chemistry, chemical physics / Chemical Society [London] - Cambridge, 1999, currens
Volume/pages
18(2016):4, p. 3234-3243
ISSN
1463-9076
ISI
000369506000106
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
Hydrogen plays an essential role during the in situ assembly of tailored catalytic materials, and serves as key ingredient in multifarious chemical reactions promoted by these catalysts. Despite intensive debate for several decades, the existence and nature of hydrogen-involved mechanisms - such as hydrogen-spillover, surface migration - have not been unambiguously proven and elucidated up to date. Here, Pt-Ga alloy formation is used as a probe reaction to study the behavior and atomic transport of H and Ga, starting from Pt nanoparticles on hydrotalcite-derived Mg(Ga)(Al)O-x supports. In situ XANES spectroscopy, time-resolved TAP kinetic experiments, HAADF-STEM imaging and EDX mapping are combined to probe Pt, Ga and H in a series of H-2 reduction experiments up to 650 degrees C. Mg(Ga)(Al)O-x by itself dissociates hydrogen, but these dissociated hydrogen species do not induce significant reduction of Ga3+ cations in the support. Only in the presence of Pt, partial reduction of Ga3+ into Ga delta+ is observed, suggesting that different reaction mechanisms dominate for Pt- and Mg(Ga)(Al)O-x-dissociated hydrogen species. This partial reduction of Ga3+ is made possible by Pt-dissociated H species which spillover onto non-reducible Mg(Al)O-x or partially reducible Mg(Ga)(Al) Ox and undergo long-range transport over the support surface. Moderately mobile Ga delta+Ox migrates towards Pt clusters, where Ga delta+ is only fully reduced to Ga-0 on condition of immediate stabilization inside Pt-Ga alloyed nanoparticles.
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Full text (open access)
https://repository.uantwerpen.be/docman/irua/233bd5/130678.pdf
E-info
https://repository.uantwerpen.be/docman/iruaauth/7216e6/132315.pdf
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