Palladium-platinum powder catalysts manufactured by colloid synthesis

Veisz, Bernadett; Tóth, Lajos; Teschner, Detre; Paál, Z.; Győrffy, Nóra; Wild, Ute; Schlögl, Robert

doi:10.1016/j.molcata.2005.04.064

Cited by 35 publications

(31 citation statements)

References 37 publications

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“…In accordance with the Ga 3d spectra that showed small amounts of zero-valent Ga at this reduction temperature, this indicates the co-existence of metallic Pd and of Pd interacting with zero-valent Ga at a beginning stage of intermetallic formation. It was possible to fit the Pd 3d region using two species: an asymmetric one (TS = 0.1, TL = 40) at a binding energy of 335.2 eV and a symmetric one at 335.7 eV, with the former value being characteristic of metallic Pd particles of the nm size regime [41][42][43]. The latter higher BE is similar to that of Pd 3d observed in unsupported bulk intermetallic Pd-Ga compounds [23] and, in combination with XRD, we therefore assign it to Pd within the IMC Pd 2 Ga. Additionally, a broad peak at approximately 342 eV is present and can be assigned to a Plasmon excitation shifted by about 6.5 eV compared with Pd 3d 5/2 [44].…”

Section: In Situ Xps During H2 Reductionmentioning

confidence: 99%

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Haghöfer

Föttinger

Girgsdies

et al. 2012

Journal of Catalysis

105

138

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Pd/Ga2O3 methanol steam reforming (MSR) catalysts were characterized in detail by utilizing a range of in situ techniques of varying surface sensitivity. Correlating the nature of the intermetallic Pd-Ga compound (IMC; formed upon reduction) with the corresponding activity/selectivity revealed pronounced differences. Generally, a dynamic response of the catalyst surface to the surrounding gas environment was observed. Special attention was paid to the bulk and surface stability of the Pd-Ga IMCs. Whereas the bulk was stable in O2, decomposition of the surface occurred resulting in a partial coverage by GaxOy islands. In addition, we focused on the formation mechanism of undesired CO and were able to identify the reasons limiting the selectivity to MSR. We observed a detrimental effect of CO on the selective Pd-Ga intermetallic compound, causing partial decomposition of the IMC to metallic Pd at the surface. Consequently, patches of Pd metal are present under reaction conditions, catalyzing the unwanted parallel methanol decomposition reaction.

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Section: In Situ Xps During H2 Reductionmentioning

confidence: 99%

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Haghöfer

Föttinger

Girgsdies

et al. 2012

Journal of Catalysis

105

138

View full text Add to dashboard Cite

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“…38,39) The Al 2s spectrum is fitted with two peaks, the peak at 117.3 eV can be assigned to the metallic state, and the other peak at 119.7 eV is from the oxidized Al 3þ state. 40) The spectrum in the range of 538-525 eV was decomposed into two peaks, in which the primary peak located at 531.1 eV is assigned to O 1s electron of the metal oxide oxygen from the surface, 33) and the minor peak at 532.4 eV may originate from Pd 3p 3=2 electrons 41) or O 1s electrons in oxygenous organic contamination. 42) In the XPS high resolution spectra, metallic forms of Zr, Pd, Ag, Fe and Al can all be confirmed, while only Zr, Pd and Al show oxidized states.…”

Section: Corrosion Behaviormentioning

confidence: 99%

Development of Ni- and Cu-Free Zr-Based Bulk Metallic Glasses for Biomedical Applications

2011

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Two Ni-and Cu-free bulk metallic glasses (BMGs) of Zr 65 Pd 17:5 Fe 10 Al 7:5 and Zr 65 Pd 12:5 Ag 5 Fe 10 Al 7:5 , with a critical casting diameter of 6 mm and a compressive strength above 1500 MPa, were developed. While the Zr 65 Pd 17:5 Fe 10 Al 7:5 alloy showed little plastic strain before fracture, the Zr 65 Pd 12:5 Ag 5 Fe 10 Al 7:5 alloy exhibited much larger plasticity by the relatively stable, intermittent propagation of the major shear band under compression. This unusual plastic deformation behavior was interpreted on the basis of the contribution of the icosahedral shortrange order. Potentiodynamic polarization tests revealed that the Zr 65 Pd 12:5 Ag 5 Fe 10 Al 7:5 alloy has a higher corrosion resistance than the Zr 65 Pd 17:5 Fe 10 Al 7:5 alloy in phosphate buffered saline at 37 C. X-ray photoelectron spectroscopy analysis revealed that the passive film of Zr 65 Pd 12:5 Ag 5 Fe 10 Al 7:5 alloy consisted mostly of ZrO 2 , which may be responsible for the excellent corrosion resistance of this alloy. Ni-and Cufree BMGs with a critical diameter of 6 mm, together with enhanced mechanical properties and corrosion resistance, may be promising in biomedical applications.

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“…XPS proved very useful for studying the composition and valence state of the components in bimetallic catalysts [37,38]. The untreated Rh-Pt contained much oxygen and carbon impurities ( Table 1).…”

Section: Xpsmentioning

confidence: 99%

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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Palladium-platinum powder catalysts manufactured by colloid synthesis

Cited by 35 publications

References 37 publications

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

In situ study of the formation and stability of supported Pd2Ga methanol steam reforming catalysts

Development of Ni- and Cu-Free Zr-Based Bulk Metallic Glasses for Biomedical Applications

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

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