High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows
The structural and redox stability of the n = 1 Ruddlesden-Popper (RP) oxide Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4-δ, synthesized by the citrate-gel method, has been investigated over the temperature range 25-700 °C under reducing (5% H 2 flow) and oxidizing (O 2 or air flow) conditions by means of in situ ne...
| Main Authors: | , , , , , , |
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| פורמט: | Journal article |
| שפה: | English |
| יצא לאור: |
2012
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| _version_ | 1826304980547534848 |
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| author | Bahout, M Tonus, F Prestipino, C Pelloquin, D Hansen, T Fonda, E Battle, P |
| author_facet | Bahout, M Tonus, F Prestipino, C Pelloquin, D Hansen, T Fonda, E Battle, P |
| author_sort | Bahout, M |
| collection | OXFORD |
| description | The structural and redox stability of the n = 1 Ruddlesden-Popper (RP) oxide Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4-δ, synthesized by the citrate-gel method, has been investigated over the temperature range 25-700 °C under reducing (5% H 2 flow) and oxidizing (O 2 or air flow) conditions by means of in situ neutron powder diffraction (NPD) and X-ray absorption near-edge structure spectroscopy (XANES). Sequential Rietveld refinement of the NPD patterns collected under hydrogen revealed de-intercalation of oxide ions from the equatorial anion positions with retention of I4/mmm symmetry. The reduction from Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4.00(2) to Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 3.81(2) is accompanied by an expansion of both the a and c lattice parameters. When the reduced sample is heated in air, oxygen refills the equatorial sites and the unit cell contracts; the interlayer interstitial site remains unoccupied. XANES showed the oxidation states in the as-prepared composition to be Pr 3+, Cr 3+ and Mn 4+. When the material is heated under dilute hydrogen, the oxidation states Pr 3+ and Cr 3+ are retained whereas Mn 4+ is reduced to Mn 3+. These observations constitute the first direct evidence that the d-block element, and not praseodymium, is responsible for the electrocatalytic activity of Pr-containing RP oxides. When the reduced material is heated under oxygen, Mn 3+ is reoxidised to Mn 4+ and a low concentration of tetrahedrally-coordinated Cr(vi) forms, suggesting a possible poisoning mechanism in fuel-cell applications. © The Royal Society of Chemistry 2012. |
| first_indexed | 2024-03-07T06:25:57Z |
| format | Journal article |
| id | oxford-uuid:f44a6e7e-71b4-433d-807e-44e7c488ff8e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T06:25:57Z |
| publishDate | 2012 |
| record_format | dspace |
| spelling | oxford-uuid:f44a6e7e-71b4-433d-807e-44e7c488ff8e2022-03-27T12:18:47ZHigh-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flowsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:f44a6e7e-71b4-433d-807e-44e7c488ff8eEnglishSymplectic Elements at Oxford2012Bahout, MTonus, FPrestipino, CPelloquin, DHansen, TFonda, EBattle, PThe structural and redox stability of the n = 1 Ruddlesden-Popper (RP) oxide Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4-δ, synthesized by the citrate-gel method, has been investigated over the temperature range 25-700 °C under reducing (5% H 2 flow) and oxidizing (O 2 or air flow) conditions by means of in situ neutron powder diffraction (NPD) and X-ray absorption near-edge structure spectroscopy (XANES). Sequential Rietveld refinement of the NPD patterns collected under hydrogen revealed de-intercalation of oxide ions from the equatorial anion positions with retention of I4/mmm symmetry. The reduction from Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 4.00(2) to Pr 0.5Sr 1.5Cr 0.5Mn 0.5O 3.81(2) is accompanied by an expansion of both the a and c lattice parameters. When the reduced sample is heated in air, oxygen refills the equatorial sites and the unit cell contracts; the interlayer interstitial site remains unoccupied. XANES showed the oxidation states in the as-prepared composition to be Pr 3+, Cr 3+ and Mn 4+. When the material is heated under dilute hydrogen, the oxidation states Pr 3+ and Cr 3+ are retained whereas Mn 4+ is reduced to Mn 3+. These observations constitute the first direct evidence that the d-block element, and not praseodymium, is responsible for the electrocatalytic activity of Pr-containing RP oxides. When the reduced material is heated under oxygen, Mn 3+ is reoxidised to Mn 4+ and a low concentration of tetrahedrally-coordinated Cr(vi) forms, suggesting a possible poisoning mechanism in fuel-cell applications. © The Royal Society of Chemistry 2012. |
| spellingShingle | Bahout, M Tonus, F Prestipino, C Pelloquin, D Hansen, T Fonda, E Battle, P High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows |
| title | High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows |
| title_full | High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows |
| title_fullStr | High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows |
| title_full_unstemmed | High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows |
| title_short | High-temperature redox chemistry of Pr0.5Sr1.5Cr0.5Mn0.5O4-delta investigated in situ by neutron diffraction and X-ray absorption spectroscopy under reducing and oxidizing gas flows |
| title_sort | high temperature redox chemistry of pr0 5sr1 5cr0 5mn0 5o4 delta investigated in situ by neutron diffraction and x ray absorption spectroscopy under reducing and oxidizing gas flows |
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