Abstract: An ESCALAB High Pressure photoelectron spectrometer specially designed by Vacuum Generators Co. (UK) for in-situ measurements at high pressures has been modified for adsorption and catalytic experiments. New construction of a gas cell, which serves to create a high-pressure zone, allows us to measure photoemission spectra in-situ at pressures up to 0.2–0.5 mbar and to use a sample holder with independent heating of a sample. This makes it possible to measure temperature programmed desorption and reaction spectra and, as a consequence, to characterize the catalytic properties simultaneously with the acquisition of X-ray photoelectron spectroscopy (XPS) data. Capabilities of the modified spectrometer are demonstrated by the examples of studies of CO and methanol adsorption on Pd(111) single crystal and methanol oxidation over Cupoly. The XPS study of high-pressure adsorption of CO on perfect and sputtered Pd(111) showed that raising the pressure has the same effect as decreasing the temperature. The CO coverage is increased due to adsorption of CO to weakly bound (on-top) state, which appears in addition to more strongly bound three-fold and bridged species. No indications of CO dissociation or carbonyl formation were found under the given experimental conditions (high pressure and sputtering-induced defects), provided that the CO gas was sufficiently clean. Two pathways of methanol decomposition to CHx, ads (x≤3) and to COads was unambiguously identified, with their contribution being dependent on P and T. The decomposition to carbon-originated species had a small contribution in UHV conditions at room temperature, but became more significant at higher pressures and temperatures. Analysis of the distribution of the reaction products and surface species during methanol oxidation over copper in the sub-millibar pressure range showed that an increase in catalytic activity observed on heating the sample from 420 to 670 K is accompanied by transformation of the adlayer composition. At low temperatures, the surface is covered by methoxy- and, to a lesser extent, formate-groups. The active surface (T > 520 K) is metallic copper with two adsorbed oxygen species. The possible nature of these species is discussed.

Cite: Bukhtiyarov V.I. , Kaichev V.V. , Prosvirin I.P.
X-Ray Photoelectron Spectroscopy as a Tool for in-situ Study of the Mechanisms of Heterogeneous Catalytic Reactions
Topics in Catalysis. 2005. V.32. N1-2. P.3-15. DOI: 10.1007/s11244-005-9254-3 WOS Scopus РИНЦ ANCAN OpenAlex

Dates:

Published print:

Feb 1, 2005

Identifiers:

Web of science:	WOS:000226939900002
Scopus:	2-s2.0-13844255276
Elibrary:	13485511
Chemical Abstracts:	2005:89741
Chemical Abstracts (print):	142:285942
OpenAlex:	W1994894222

Citing:

DB	Citing
Web of science	73
Scopus	74
Elibrary	81
OpenAlex	76

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