X-ray absorption studies of some platinum oxides

Mansour, A. N.; Sayers, D. E.; Cook, J. W.; Short, David R.; Shannon, R. D.; Katzer, J.R.

doi:10.1021/j150653a022

Cited by 52 publications

(41 citation statements)

References 3 publications

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“…It can be seen that the average value of PtÀ O bond distance is nearly 2.00 Å, regardless of the temperature under which the functioning catalyst was meas-ured. The interatomic distance obtained is characteristic to platinum oxides [64] and similar to early reports for Pt/CeO 2 systems. [10,58,65] A coordination number (CN) of the first coordination shell (PtÀ O) is~5.7(4) for the as-prepared catalyst and 4.8(4) for the activated catalyst.…”

Section: Operando Xafs Study Of Pto X /Ceo 2 Catalystssupporting

confidence: 88%

Cerium(III) Nitrate Derived CeO₂ Support Stabilising PtO_x Active Species for Room Temperature CO Oxidation

et al. 2020

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A new approach for preparing a PtOx/CeO2 catalyst for low‐temperature CO oxidation has been developed. The approach includes; i) preparation of a CeO2 support through the controllable thermal decomposition of Ce(NO3)3 ⋅ 6H2O, and then ii) deposition of polynuclear platinum nitrato complexes ([H3O⊂18‐crown‐6]2[Pt2(μ2‐OH)2(NO3)8][Pt4(μ3‐OH)2(μ2‐OH)4(NO3)10]) on the CeO2 support. The NO3−‐rich ceria support produced at the onset temperature of Ce(NO3)3 ‐> CeO2 transformation (220 °C) yields the “PtOx/CeO2‐220” catalyst that shows intriguingly high activity in CO oxidation, at room temperature and below. To understand the nature of the low‐temperature catalytic activity, prepared catalysts have been studied using X‐ray photoelectron spectroscopy (XPS), Raman and operando X‐ray absorption fine structure spectroscopy (XAFS) and transmission electron microscopy (TEM).

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Section: Operando Xafs Study Of Pto X /Ceo 2 Catalystssupporting

confidence: 88%

Cerium(III) Nitrate Derived CeO₂ Support Stabilising PtO_x Active Species for Room Temperature CO Oxidation

et al. 2020

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“…2a), the features are strongly enhanced with more spectral details due to the reduction of the Pt 2p core hole lifetime broadening. The strong white-line intensity and the "dip" in the post-edge region at high potentials are characteristic spectral features of platinum oxides 29 .…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

In situ X-ray probing reveals fingerprints of surface platinum oxide

Friebel

Miller

O’Grady

et al. 2011

Phys. Chem. Chem. Phys.

109

107

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In situ x-ray absorption spectroscopy (XAS) at the Pt L 3 edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard x-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF8 code and complementary extended x-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.

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“…15,34 The methodology for the XANES data analysis followed the procedure described by Meitzner et al 35 The methodology used to determine the Pt 5 d-orbital vacancies are based on earlier work by Mansour and co-workers. 36,37 In situ XAS data at the Pt L (L 3 and L 2 ) and Ru, and Mo K-edges were taken at 0.54 V using a computer-interfaced potentiostat/galvanostat ͑Solartron model 1287͒ and Scribner software ͑Corrware͒. The electrolyte of choice was 1 M HClO 4 .…”

Section: Methodsmentioning

confidence: 99%

Electrocatalysis of CO Tolerance by Carbon-Supported PtMo Electrocatalysts in PEMFCs

Mukerjee

Urian

Lee

et al. 2004

J. Electrochem. Soc.

120

104

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This paper is a full version of an earlier short communication, where significantly higher ͑up to threefold͒ CO tolerance was reported for PtMo/C ͑atomic ratio, Pt:Mo, 3:1͒ relative to the current state-of-the-art PtRu/C ͑1:1͒ in a proton exchange membrane fuel cell ͑PEMFC͒ under standard operating conditions ͑85°C, 100% humidification, with H 2 ϩ 100 pm CO//O 2 ). We report significantly different behavior for PtMo/C in contrast to PtRu/C, wherein there is negligible variation in CO tolerance ͑100 ppm CO in H 2 ) with variations in alloying compositions ͑Pt:Mo, 1:1 to 5:1͒. Further, in contrast to Pt/C and PtRu/C, significantly lower variations in overpotential losses is observed for PtMo/C as a function of temperature ͑55-115°C͒ and CO concentrations ͑5-100 ppm, balance H 2 ). In addition, excellent long-term stability is reported for PtMo/C ͑1:1͒ under steady-state conditions ͑constant potential conditions at 0.6 V͒ for a total duration of 1500 h, with anode gas composition varied between pure H 2 and those with 100 ppm CO, with or without the presence of other reformate gases ͑primarily CO 2 and N 2 ). These are discussed in the context of detailed physicochemical characterization of the nanoparticles using a combination of X-ray diffraction, transmission electron microscopy, and in situ synchrotron X-ray absorption spectroscopy.CO tolerance in reformer-based low-and medium-temperature proton exchange membrane fuel cells ͑PEMFCs͒ is crucial for the viability of this technology for transportation and portable power applications. The choice of an appropriate anode electrocatalyst with low susceptibility to CO poisoning and a high kinetic rate for hydrogen oxidation is therefore paramount. Despite its superior activity for anodic, hydrogen oxidation, and interfacial stability under acidic pH conditions and the operating temperatures of an actual PEMFC, electrocatalysis by Pt/C suffers from the problem of high polarization losses due to CO poisoning. This is especially true for temperatures below 115°C.The large affinity for CO chemisorption at potentials lower than ϳ0.65 V on Pt/C necessitates the search for other nanophase Ptbased electrocatalysts capable of initiating CO oxidation, preferably close to the hydrogen oxidation potential. This need manifested in the ''bifunctional'' 1,2 approach, where a second, more oxidizable element, present either as an admetal or as an alloying element, initiates the CO oxidation at lower potentials. The result is enough bare surface on Pt crystallites to efficiently oxidize hydrogen at lower overpotentials.Prior literature, involving several decades of research, is replete with investigations of alloys such as PtSn, 3,4 PtRh, 5 PtRu, 6-8 and Pt with adsorbing adatoms such as Ge, Sb, and Sn, 2,9 etc. In recent years nanophase PtRu electrocatalysts have received renewed attention as promising candidates for CO oxidation in PEMFCs. 10-12 A recent report by Oetjen et al., 13 using steady-state polarization data, indicates a fourfold performance enhancement with highly dispersed ...

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X-ray absorption studies of some platinum oxides

Cited by 52 publications

References 3 publications

Cerium(III) Nitrate Derived CeO₂ Support Stabilising PtO_x Active Species for Room Temperature CO Oxidation

Cerium(III) Nitrate Derived CeO₂ Support Stabilising PtO_x Active Species for Room Temperature CO Oxidation

In situ X-ray probing reveals fingerprints of surface platinum oxide

Electrocatalysis of CO Tolerance by Carbon-Supported PtMo Electrocatalysts in PEMFCs

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X-ray absorption studies of some platinum oxides

Cited by 52 publications

References 3 publications

Cerium(III) Nitrate Derived CeO2 Support Stabilising PtOx Active Species for Room Temperature CO Oxidation

Cerium(III) Nitrate Derived CeO2 Support Stabilising PtOx Active Species for Room Temperature CO Oxidation

In situ X-ray probing reveals fingerprints of surface platinum oxide

Electrocatalysis of CO Tolerance by Carbon-Supported PtMo Electrocatalysts in PEMFCs

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Product

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Cerium(III) Nitrate Derived CeO₂ Support Stabilising PtO_x Active Species for Room Temperature CO Oxidation

Cerium(III) Nitrate Derived CeO₂ Support Stabilising PtO_x Active Species for Room Temperature CO Oxidation