The Free Energy of Formation of Palladium Oxide

Warner, Julie

doi:10.1149/1.2426509

Cited by 48 publications

(18 citation statements)

References 4 publications

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“…Similar TG and DTA curves were also measured for the oxidation of amorphous PdZr3. Calculations based on thermodynamic data [7] indicate that under air PdO decomposition is expected to start at about 800"C, which is in agreement with the experimental results shown in Fig. 3.…”

Section: Oxidation Of Amorphous Palladium-zirconium Alloyssupporting

confidence: 87%

Transformation of Glassy Palladium‐Zirconium Alloys to Highly Active CO‐Oxidation Catalysts During In Situ Activation Studied by Thermoanalytical Methods and X‐Ray Diffraction

Baiker

Maciejewski

Tagliaferri

1993

Ber Bunsenges Phys Chem

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Alloy I Catalysis I Glasses I Materials Properties I MetalsPalladiudzirconia catalysts highly active for the oxidation of CO can be prepared by exposing amorphous Pd-Zr alloys to CO oxidation conditions at 280°C. The bulk chemical and structural changes occuring under these conditions have been studied using thermoanalytical methods (TG, DTA) combined with mass spectrometry and in-situ powder XRD. Amorphous PdZr2 and PdZr3 alloys exhibit virtually no activity when exposed to CO oxidation conditions, mainly due to their low specific surface area (-0.01 m'lg). The activity develops with time on stream, passes through a maximum and reaches a stable state only after several hours. The maximum in the activity is observed when about 50-70% of the amount of oxygen necessary for complete oxidation of the precursor to PdO and Zr02 has been consumed. The oxidation of the amorphous Pd-Zr alloys, which results in a drastic increase of the specific surface area of the samples, starts at significantly lower temperature than the crystallization temperatures of the alloys. The stable catalysts contain poorly crystalline monoclinic and tetragonal ZrOz, metallic palladium and PdO as bulk phases. The concentration of these phases is influenced by a series of simultaneously occurring reactions, including: the oxidation of the alloy constituents by O2 which results in PdO and Zr02, the oxidation by COz resulting in Pd and Zr02, and the reduction of the PdO formed by CO and by metallic Zr present in the unreacted part of the alloy. The solid state reduction 2 PdO + Zr -Pd + ZrOz contributes significantly to the reduction of the PdO as long as metallic Zr is abundant in the alloys.

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Section: Oxidation Of Amorphous Palladium-zirconium Alloyssupporting

confidence: 87%

Transformation of Glassy Palladium‐Zirconium Alloys to Highly Active CO‐Oxidation Catalysts During In Situ Activation Studied by Thermoanalytical Methods and X‐Ray Diffraction

Baiker

Maciejewski

Tagliaferri

1993

Ber Bunsenges Phys Chem

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“…For example, Smirnov and Graham [34] showed that Pd films that had been vapor deposited onto ceria-zirconia substrates could be completely oxidized by heating to 423 K in ultra-high vacuum. Given that oxygen binding is much stronger on reduced ceria-zirconia than it is on Pd [28,30,35], this transfer of oxygen must be endothermic, suggesting that the driving force for oxygen transfer from ceria-zirconia to Pd is entropic. A similar situation may occur with CeO 2 and MnO, even though this reaction should also be endothermic.…”

Section: Discussionmentioning

confidence: 99%

A Study of Cerium–Manganese Mixed Oxides for Oxidation Catalysis

2007

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Cerium-manganese mixed oxides with compositions of Ce 0.5 Mn 0.5 O 1.75 and Ce 0.8 Mn 0.2 O 1.9 were prepared by the citric-acid (Pechini) method and their catalytic properties were compared to CeO 2 and Mn 2 O 3 . The mixed oxides exhibited higher specific rates than either CeO 2 or Mn 2 O 3 for oxidation of both methane and n-butane. While XRD measurements of the mixed oxides suggested that the materials had primarily the fluorite structure, oxygen isotherms, measured by coulometric titration at 973 K, exhibited steps associated with MnO-Mn 3 O 4 and Mn 3 O 4 -Mn 2 O 3 equilibria, implying that manganese oxide must exist as separate phases in the solids. The P(O 2 ) for the MnO-Mn 3 O 4 equilibrium is shifted to lower values in the mixed oxides, indicating that the manganese-oxide phase is affected by interactions with ceria.

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“…Dedicated environmental TEMs (ETEM) can allow high resolution imaging and spectroscopy in a gaseous environment, but are limited to mbar-range pressures [3][4][5][6]. To simulate operando conditions for many relevant systems, higher pressures are needed: the decomposition temperature of PdO in O 2 , for instance, changes by nearly 300 degrees between 1 mbar and 1 atm [7][8][9]. There have been several reports of greater-than-atmospheric pressures using customized stages in which the gas is contained between two semi-transparent windows, typically a pair of amorphous SiN membranes separated by less than 100 mm [10][11][12][13][14][15][16][17]22,23].…”

Section: Introductionmentioning

confidence: 99%

A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

et al. 2015

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Environmental transmission electron microscopy (TEM) has enabled in situ experiments in a gaseous environment with high resolution imaging and spectroscopy. Addressing scientific challenges in areas such as catalysis, corrosion, and geochemistry can require pressures much higher than the ∼20 mbar achievable with a differentially pumped environmental TEM. Gas flow stages, in which the environment is contained between two semi-transparent thin membrane windows, have been demonstrated at pressures of several atmospheres. However, the relationship between the pressure at the sample and the pressure drop across the system is not clear for some geometries. We demonstrate a method for measuring the gas pressure at the sample by measuring the ratio of elastic to inelastic scattering and the defocus of the pair of thin windows. This method requires two energy filtered high-resolution TEM images that can be performed during an ongoing experiment, at the region of interest. The approach is demonstrated to measure greater than atmosphere pressures of N2 gas using a commercially available gas-flow stage. This technique provides a means to ensure reproducible sample pressures between different experiments, and even between very differently designed gas-flow stages.

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The Free Energy of Formation of Palladium Oxide

Cited by 48 publications

References 4 publications

Transformation of Glassy Palladium‐Zirconium Alloys to Highly Active CO‐Oxidation Catalysts During In Situ Activation Studied by Thermoanalytical Methods and X‐Ray Diffraction

Transformation of Glassy Palladium‐Zirconium Alloys to Highly Active CO‐Oxidation Catalysts During In Situ Activation Studied by Thermoanalytical Methods and X‐Ray Diffraction

A Study of Cerium–Manganese Mixed Oxides for Oxidation Catalysis

A method for measuring the local gas pressure within a gas-flow stage in situ in the transmission electron microscope

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