Identification of two types of oxidized palladium on γ-alumina by X-ray photoelectron spectroscopy

Otto, K.; Haack, Larry P.; deVries, J.E.

doi:10.1016/0926-3373(92)80003-i

Cited by 188 publications

(80 citation statements)

References 16 publications

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“…Both Pd and La characteristic X-ray peaks are seen in the spectrum, indicating that these elements are present on the g-alumina support at concentrations high enough to be detected by EDS but otherwise not visible in the HAADF images. The average concentration of the atomically dispersed Pd was estimated to be B0.5 wt% and this loading is similar to that seen previously in automotive catalysts for the 'oxidized' form of Pd, which was thought to interact strongly with the alumina support 16 .…”

Section: Resultssupporting

confidence: 59%

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Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

et al. 2014

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Catalysis by single isolated atoms of precious metals has attracted much recent interest, as it promises the ultimate in atom efficiency. Most previous reports are on reducible oxide supports. Here we show that isolated palladium atoms can be catalytically active on industrially relevant g-alumina supports. The addition of lanthanum oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated palladium atoms. Aberration-corrected scanning transmission electron microscopy and operando X-ray absorption spectroscopy confirm the presence of intermingled palladium and lanthanum on the g-alumina surface. Carbon monoxide oxidation reactivity measurements show onset of catalytic activity at 40°C. The catalyst activity can be regenerated by oxidation at 700°C in air. The high-temperature stability and regenerability of these ionic palladium species make this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

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Section: Resultssupporting

confidence: 59%

“…In the case of palladium, XPS observations by Otto et al 16 demonstrated the existence of two types of palladium oxide present on g-alumina. One oxide was characterized by relatively large particles with a Pd 3d binding energy characteristic of PdO, and which could be readily transformed to Pd metal at room temperature in hydrogen.…”

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confidence: 99%

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

et al. 2014

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“…50 The second shoulder peak centred at a binding energy of 337.6 eV, can typically be assigned to the presence of highly oxidized Pd species such as PdO2 (reported in the range between 337.2 -338.2 eV). [51][52][53] As the cubic NCs age over 6 months the PdOx peak intensity increased, which can be seen from comparison of the Pd 3d spectra in figure 5(a)-(c). The nature of the surface facets present in the NCs is important for understanding the oxidation behaviour of faceted NCs.…”

Section: Oxidation and Interaction Of Pvp With Pd Nanocrystalsmentioning

confidence: 79%

Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals

et al. 2014

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Access to the full text of the published version may require a subscription. Rights © 2014 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form AbstractA critical aspect in the practical application and enhanced catalytic performance of shape controlled nanocrystals is their stability and morphology retention under ambient conditions.Changes to the morphology of shape-controlled Pd nanocrystals capped by PVP are assessed by TEM and surface oxidation was evaluated by X-ray photoelectron spectroscopy (XPS), over 12 months. Surface oxidation of PVP-capped Pd nanocrystals resulted in loss of edge and corner sites and transition to spherical morphologies. The shape stability of the nanocrystals was found to follow the trend cubic < cuboctahedra < octahedral ~ concave cubes. For low index planes, {111} surfaces are more resistant to oxidation compared to {100} facets, correlating with the surface free energy of the nanocrystals. Cubic and cuboctahedral nanocrystals transitioned to spherical particles while octahedral nanocrystals retained their morphology. The presence of high energy {110} facets were observed in the cubic nanocrystals which undergo surface reconstruction. The presence of surface defects such as stacking faults were also found to influence the rate of the structural changes.Concave cubic nanocrystals, which possess high index facets and surface energies were consistently found to display excellent morphology retention. The concave cubic 2 nanocrystals displayed superior shape stability and reduced oxidation compared to cubic and cuboctahedral nanocrystals. XPS analysis further determined that PVP capping ligands on different Pd surface facets strongly influences the morphological consistency. The stability of the concave cubes can be attributed to stronger chemisorption of PVP capping ligands to the high index plane making them less susceptible to oxidation.

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“…11(b)), Pd3d spectrum gives a peak with E b (Pd3d 5/2 ) 335.6 eV, which is assigned to small metal particles. Bulk metal palladium is known to have E b of Pd3d 5/2 at 335.2 eV (Brun et al, 1999;Otto et al, 1992). In our case, a small increase of E b is likely to originate from the size effect (Mason, 1983).…”

Section: State Of Palladium In Pd/sz Catalystsmentioning

confidence: 85%

FTIR Spectroscopy of Adsorbed Probe Molecules for Analyzing the Surface Properties of Supported Pt (Pd) Catalysts

Belskaya¹,

Данилова²,

Казаков³

et al. 2012

Infrared Spectroscopy - Materials Science, Engineering and Technology

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Identification of two types of oxidized palladium on γ-alumina by X-ray photoelectron spectroscopy

Cited by 188 publications

References 16 publications

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals

FTIR Spectroscopy of Adsorbed Probe Molecules for Analyzing the Surface Properties of Supported Pt (Pd) Catalysts

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