Surface and bulk structural response of Pt black upon its hydrogen treatment and catalytic reaction with n-hexane

Z. Paál, U. Wild, A. Wootsch, J. Find, R. Schlögl

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Pt black has been studied by X-ray and ultraviolet photoelectron spectroscopies (XPS, UPS) and XRD after reduction, after presintering and after subjection to various in situ treatments. All samples contained carbon and oxygen impurities. Sintering decreased the abundance of C. Samples introduced from the air contained a large amount of oxygen whose amount dropped markedly upon keeping the Pt in UHV for several hours. XPS and UPS revealed considerable amounts of nondissociatively chemisorbed CO after this treatment. An in situ hydrogen treatment at 603 K decreased the O content further but increased the concentration of surface carbon. The Pt 4f regions showed some oxidized Pt both before and after sintering. Pt reached an almost clean metallic state after UHV treatment. This state seemed to remain unchanged after further manipulations. Hardly any electronic interaction could thus be observed between Pt and its main impurity: C, which was present mostly as graphite and CxHy polymer after treatment with n-hexane plus hydrogen. n-Hexane alone produced mostly "disordered" surface carbon species. The intensity of higher-order X-ray reflections of Pt was suppressed upon sintering. This anisotropy was reversed after in situ H2 treatments, inducing recrystallization with preferential formation of higher Miller-index planes, (220) and (311). These reflections were again suppressed after exposure to n-hexane. Thus, adsorbate-induced solid-state rearrangement occurred as a result of the interplay of surface and subsurface impurities. The catalytic reactions of n-hexane over Pt black subjected to different pretreatments were different: abundant (220) and (311) reflections promoting isomerisation, C5-cyclisation and also hydrogenolysis. Carbon accumulation decreased the "intrinsic" activity of the Pt fraction detected by XPS. Selectivities, in turn, were governed by the crystallite structure as well as by the presence of composite platinum-carbon sites. "Disordered" surface carbon species poisoned all skeletal reactions and favoured dehydrogenation to hexenes.

Original languageEnglish
Pages (from-to)2148-2155
Number of pages8
JournalPhysical Chemistry Chemical Physics
Volume3
Issue number11
DOIs
Publication statusPublished - 2001

Fingerprint

Hydrogen
Carbon
carbon
sintering
hydrogen
X ray photoelectron spectroscopy
Sintering
Impurities
impurities
Ultraviolet photoelectron spectroscopy
Oxygen
hydrogenolysis
Hydrogenolysis
hexenes
Graphite
Cyclization
ultraviolet spectroscopy
oxygen
Dehydrogenation
Adsorbates

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics

Cite this

Surface and bulk structural response of Pt black upon its hydrogen treatment and catalytic reaction with n-hexane. / Paál, Z.; Wild, U.; Wootsch, A.; Find, J.; Schlögl, R.

In: Physical Chemistry Chemical Physics, Vol. 3, No. 11, 2001, p. 2148-2155.

Research output: Contribution to journalArticle

@article{c7d25d6b25f848deb6607124572bf921,
title = "Surface and bulk structural response of Pt black upon its hydrogen treatment and catalytic reaction with n-hexane",
abstract = "Pt black has been studied by X-ray and ultraviolet photoelectron spectroscopies (XPS, UPS) and XRD after reduction, after presintering and after subjection to various in situ treatments. All samples contained carbon and oxygen impurities. Sintering decreased the abundance of C. Samples introduced from the air contained a large amount of oxygen whose amount dropped markedly upon keeping the Pt in UHV for several hours. XPS and UPS revealed considerable amounts of nondissociatively chemisorbed CO after this treatment. An in situ hydrogen treatment at 603 K decreased the O content further but increased the concentration of surface carbon. The Pt 4f regions showed some oxidized Pt both before and after sintering. Pt reached an almost clean metallic state after UHV treatment. This state seemed to remain unchanged after further manipulations. Hardly any electronic interaction could thus be observed between Pt and its main impurity: C, which was present mostly as graphite and CxHy polymer after treatment with n-hexane plus hydrogen. n-Hexane alone produced mostly {"}disordered{"} surface carbon species. The intensity of higher-order X-ray reflections of Pt was suppressed upon sintering. This anisotropy was reversed after in situ H2 treatments, inducing recrystallization with preferential formation of higher Miller-index planes, (220) and (311). These reflections were again suppressed after exposure to n-hexane. Thus, adsorbate-induced solid-state rearrangement occurred as a result of the interplay of surface and subsurface impurities. The catalytic reactions of n-hexane over Pt black subjected to different pretreatments were different: abundant (220) and (311) reflections promoting isomerisation, C5-cyclisation and also hydrogenolysis. Carbon accumulation decreased the {"}intrinsic{"} activity of the Pt fraction detected by XPS. Selectivities, in turn, were governed by the crystallite structure as well as by the presence of composite platinum-carbon sites. {"}Disordered{"} surface carbon species poisoned all skeletal reactions and favoured dehydrogenation to hexenes.",
author = "Z. Pa{\'a}l and U. Wild and A. Wootsch and J. Find and R. Schl{\"o}gl",
year = "2001",
doi = "10.1039/b007837i",
language = "English",
volume = "3",
pages = "2148--2155",
journal = "Physical Chemistry Chemical Physics",
issn = "1463-9076",
publisher = "Royal Society of Chemistry",
number = "11",

}

TY - JOUR

T1 - Surface and bulk structural response of Pt black upon its hydrogen treatment and catalytic reaction with n-hexane

AU - Paál, Z.

AU - Wild, U.

AU - Wootsch, A.

AU - Find, J.

AU - Schlögl, R.

PY - 2001

Y1 - 2001

N2 - Pt black has been studied by X-ray and ultraviolet photoelectron spectroscopies (XPS, UPS) and XRD after reduction, after presintering and after subjection to various in situ treatments. All samples contained carbon and oxygen impurities. Sintering decreased the abundance of C. Samples introduced from the air contained a large amount of oxygen whose amount dropped markedly upon keeping the Pt in UHV for several hours. XPS and UPS revealed considerable amounts of nondissociatively chemisorbed CO after this treatment. An in situ hydrogen treatment at 603 K decreased the O content further but increased the concentration of surface carbon. The Pt 4f regions showed some oxidized Pt both before and after sintering. Pt reached an almost clean metallic state after UHV treatment. This state seemed to remain unchanged after further manipulations. Hardly any electronic interaction could thus be observed between Pt and its main impurity: C, which was present mostly as graphite and CxHy polymer after treatment with n-hexane plus hydrogen. n-Hexane alone produced mostly "disordered" surface carbon species. The intensity of higher-order X-ray reflections of Pt was suppressed upon sintering. This anisotropy was reversed after in situ H2 treatments, inducing recrystallization with preferential formation of higher Miller-index planes, (220) and (311). These reflections were again suppressed after exposure to n-hexane. Thus, adsorbate-induced solid-state rearrangement occurred as a result of the interplay of surface and subsurface impurities. The catalytic reactions of n-hexane over Pt black subjected to different pretreatments were different: abundant (220) and (311) reflections promoting isomerisation, C5-cyclisation and also hydrogenolysis. Carbon accumulation decreased the "intrinsic" activity of the Pt fraction detected by XPS. Selectivities, in turn, were governed by the crystallite structure as well as by the presence of composite platinum-carbon sites. "Disordered" surface carbon species poisoned all skeletal reactions and favoured dehydrogenation to hexenes.

AB - Pt black has been studied by X-ray and ultraviolet photoelectron spectroscopies (XPS, UPS) and XRD after reduction, after presintering and after subjection to various in situ treatments. All samples contained carbon and oxygen impurities. Sintering decreased the abundance of C. Samples introduced from the air contained a large amount of oxygen whose amount dropped markedly upon keeping the Pt in UHV for several hours. XPS and UPS revealed considerable amounts of nondissociatively chemisorbed CO after this treatment. An in situ hydrogen treatment at 603 K decreased the O content further but increased the concentration of surface carbon. The Pt 4f regions showed some oxidized Pt both before and after sintering. Pt reached an almost clean metallic state after UHV treatment. This state seemed to remain unchanged after further manipulations. Hardly any electronic interaction could thus be observed between Pt and its main impurity: C, which was present mostly as graphite and CxHy polymer after treatment with n-hexane plus hydrogen. n-Hexane alone produced mostly "disordered" surface carbon species. The intensity of higher-order X-ray reflections of Pt was suppressed upon sintering. This anisotropy was reversed after in situ H2 treatments, inducing recrystallization with preferential formation of higher Miller-index planes, (220) and (311). These reflections were again suppressed after exposure to n-hexane. Thus, adsorbate-induced solid-state rearrangement occurred as a result of the interplay of surface and subsurface impurities. The catalytic reactions of n-hexane over Pt black subjected to different pretreatments were different: abundant (220) and (311) reflections promoting isomerisation, C5-cyclisation and also hydrogenolysis. Carbon accumulation decreased the "intrinsic" activity of the Pt fraction detected by XPS. Selectivities, in turn, were governed by the crystallite structure as well as by the presence of composite platinum-carbon sites. "Disordered" surface carbon species poisoned all skeletal reactions and favoured dehydrogenation to hexenes.

UR - http://www.scopus.com/inward/record.url?scp=0034743138&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034743138&partnerID=8YFLogxK

U2 - 10.1039/b007837i

DO - 10.1039/b007837i

M3 - Article

AN - SCOPUS:0034743138

VL - 3

SP - 2148

EP - 2155

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 11

ER -