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Find, Josef; Paál, Z.; Schlögl, Robert; Wild, Ute

doi:10.1023/a:1019037926168

Cited by 19 publications

(25 citation statements)

References 26 publications

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“…Subsequent H 2 treatments increased somewhat the amount of surface carbon. An analogous phenomenon was observed on monometallic Pt black [25,30], indicating a solid-state transformation bringing out some subsurface carbon to the surface that contained both graphitic and slightly oxidized C (with single C-O bonds). The presence [26,42].…”

Section: Xpssupporting

confidence: 59%

“…A Leybold LHS 12 MCD instrument with a MgKα anode for XPS (pass energy, PE = 48 eV) was used, as reported earlier [23,29,30]. The binding energy (BE) was calibrated to the Au 4f 7/2 line (BE = 84.0 eV).…”

Section: Xpsmentioning

confidence: 99%

“…The specific surface for Pt was 2.64 m2 g−1 (BET, N 2 adsorption) [30]. The dispersion D = 0.9%) was measured by H 2 chemisorption and was used for calculation of turnover frequencies (TOFs) [27].…”

Section: Catalytic Tests and Pretreatmentsmentioning

confidence: 99%

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Preparation, physical characterization and catalytic properties of unsupported Pt–Rh catalyst

Paál

Győrffy

Wootsch

et al. 2007

Journal of Catalysis

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Rh was deposited on a parent platinum black catalyst by an underpotential deposition method. Mean particle size and bulk composition of this Rh-Pt sample was determined by TEM and EDS. No individual Rh grains could be observed, but Rh was present in the near-surface regions, according to energy-filtered TEM images. The surface-sensitive cyclic voltammetry indicated 15-20% Rh on the surface. XPS, in turn, detected ∼ 2-2.5% Rh in the information depth. The Rh-Pt catalyst was tested in methylcyclopentane hydrogenative ring-opening reaction between 468 and 603 K and 8 to 64 kPa H 2 pressure (with 1.3 kPa MCP). The parent Pt black as well as a Rh black catalyst was also studied for comparison. MCP produced ring opening and hydrogenolysis products. The ring-opening products (ROP) consisted of 2-and 3-methylpentane (2MP and 3MP) as well as hexane (nH). These were the main products, together with some fragments and unsaturated hydrocarbons. The amount of the latter class increased at higher temperatures. The selectivities of ROP, fragments, and benzene over Rh-Pt catalyst as a function of temperature were between the values observed on Pt and Rh. The hydrogen pressure dependence of selectivities on Rh-Pt was more similar to that observed on Pt. Four subsequent treatments with O 2 and H 2 up to T = 673 K were applied on the bimetallic catalyst, followed by XPS and catalytic runs, respectively. These treatments promoted structural rearrangement, with XPS detecting less Rh in the near-surface region, partly as oxidized Rh after O 2 treatment. The catalytic behavior became more Pt-like on these structural and composition changes. We concluded that adding a relatively small amount of Rh to Pt creates bimetallic active sites with properties different from those of its components, behaving as a true bimetallic catalyst.

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Section: Xpssupporting

confidence: 59%

Section: Xpsmentioning

confidence: 99%

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Preparation, physical characterization and catalytic properties of unsupported Pt–Rh catalyst

Paál

Győrffy

Wootsch

et al. 2007

Journal of Catalysis

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“…The structural rearrangement of Pt during hydrocarbon treatments was also observed by XRD [22,23,46] (Figure 4). The relative intensities of individual diffraction peaks of an untreated Pt (just sintered) corresponded roughly to the intensity ratios of a perfect crystal, 3 although higher-order reflections (311), (222) had somewhat lower intensities.…”

Section: What Can We Learn About the Interaction Of A Hydrocarbon Reamentioning

confidence: 83%

“…A slight line broadening appeared, due to the small crystallite sizes [22]. Sintering decreased the intensities of higher-angle lines, while subsequent H 2 treatments at 473-603 K reversed this tendency [22,23].…”

Section: The Way From An Inorganic Preparation To a Catalystmentioning

confidence: 97%

Investigation of a traditional catalyst by contemporary methods: Parallel electron spectroscopic and catalytic studies on Pt black

Paál

Schlögl

2009

Surface Science

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Results of electron spectroscopy (XPS and UPS) of platinum black catalyst measured in various states of the catalyst have been summarized. XPS showed up to almost 50% carbon and up to 20% oxygen on a sample stored in air. These, however, had almost no influence on the chemical state of Pt, except for the appearance of minor surface oxide. A Pt purity of ~90% could be reached by regeneration with O 2 and H 2 . The C 1s peak contained several components from individual C atoms to graphitic and polymeric hydrocarbon layers. Thus, the active catalyst was not clean Pt but metallic Pt; the impurities exerting little influence on catalytic activity. Regeneration and deactivation led also to slight structural rearrangement, as detected by XRD. Intentional deactivation with hydrocarbon-hydrogen mixtures was monitored by XPS, UPS and catalytic tests. Correlation was found between catalytic activity and selectivity in hexane reaction and the amount -and also the chemical state -of carbon accumulated during deactivating runs. A short summary of electron spectroscopy of supported Pt catalysts is also given. The main underlying idea regards solid catalyst and reactants as a dynamic system, including also solid-state changes of the former.

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X‐Ray Photoelectron Spectroscopy in Analysis of SurfacesUpdate based on the original article by Steffen Oswald,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

Oswald

2013

Encyclopedia of Analytical Chemistry

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X‐ray photoelectron spectroscopy (XPS) is an analytical technique that uses photoelectrons excited by X‐ray radiation (usually Mg Kα or Al Kα) for the characterization of surfaces to a depth of 2–5 nm. Elemental identification and information on chemical bonding are derived from the measured electron energy and energy shifts, respectively. The use of ultrahigh vacuum (UHV) during analysis requires special sample handling. Depth profiling is possible using ion sputtering. In contrast to the most popular surface analytical technique, Auger electron spectroscopy (AES), nonconducting material can be investigated, weak material damage occurs, and the chemical shifts are easier to interpret. However, the lateral resolution of the complementary AES technique (typically down to 20 nm) is much better than for XPS (50 µm for standard equipment, down to lower than 3 µm for dedicated instruments). The detection limit (of about 0.1 at%) is not as low as for mass spectroscopic techniques, but the quantification from XPS peak area measurements is more reliable, even disclaiming standard sample measurements. This article briefly discusses the principles of the technique, sample requirements, and the typical measuring strategy. Possible information sources (elements, chemical bonding, depth and lateral distributions) are described and their quantification principles are summarized. The main part deals with typical applications relating to several material classes (metals, semiconductors, insulators, and polymers) to give an impression of the capabilities of the method over a wide range of research and technological problems. A comparison with further complementary analytical techniques is given as a summary. Technological developments in electronics, nanotechnology, polymers, biotechnology, and medicine are all concerned with surface‐related phenomena, suggesting sustained interest in XPS in the foreseeable future.

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Untitled

Cited by 19 publications

References 26 publications

Preparation, physical characterization and catalytic properties of unsupported Pt–Rh catalyst

Preparation, physical characterization and catalytic properties of unsupported Pt–Rh catalyst

Investigation of a traditional catalyst by contemporary methods: Parallel electron spectroscopic and catalytic studies on Pt black

X‐Ray Photoelectron Spectroscopy in Analysis of SurfacesUpdate based on the original article by Steffen Oswald,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.

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