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Recent Results on Dopant influenced Chemical Expansion and Surface Alteration of Ceria

Knoblauch, Nicole und Lee, Kangjae und Alkan, Gözde und Mechnich, Peter und Pein, Mathias und Agrafiotis, Christos und Roeb, Martin (2023) Recent Results on Dopant influenced Chemical Expansion and Surface Alteration of Ceria. SolarPACES, 2023-10-10 - 2023-10-13, Sydney.

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Kurzfassung

The utilization of clean and sustainable energy becomes important for solving global environmental problems and securing future energy supply. A possible method for producing CO for fuels is a two-step CO2 splitting reaction in a solar thermo-chemical cycle. Especially doped CeO2 are considered as promising redox materials for thermochemical purposes [1]. Redox studies on dense Ce-Zr-O, Ce-La-O, Ce-Yb-O, Ce-Zr–La-O and Ce-Zr–Yb-O ceramics were carried out by thermogravimetric investigations and dilatometry. The reduction state determined by both methods correspond to each other up to 1500 K under low pressure (p= 2x10-5 mbar). At higher temperatures, the thermogravimetry deviates from the actual degree of reduction, since the mass loss is not only due to reduction but also due to the selective evaporation of CeO2, whose vapour pressure is higher than that of the doping ions [2]. As a result, there is an accumulation of doping ions, which leads to a porous surface zone. Surface enrichment of zirconia is detrimental for reoxidazion kinetic of CO2 or H2O splitting reaction since re-oxidation temperatures of (Ce,Zr)O2−δ are known to be shifted towards lower temperatures with increasing ZrO2 content [3-5]. Additional doping with trivalent doping ions such as La3+ and Yb3+ can influence this selective evaporation. The evaporation zone in the form of a porous surface layer is much smaller with Ce-Zr-O pellets additionally doped with La3+ and Yb3+. Samples co-doped with La3+ and Yb3+ exhibited also high oxidation kinetics that were much faster than 10mol% Zr-doped ceria. Additionally, the extrinsic oxygen vacancies introduced by the trivalent dopants influence the chemical expansion/contraction of the ceria crystal lattice during the redox reaction. Thus, the chemical expansion during reduction is higher for trivalent doped ceria than for tetravalent doped ceria. Since the chemical expansion/contraction is influenced by the mobility and preferential localization of the intrinsic oxygen vacancies in addition to the ionic radii [6-10], it can be assumed that additional extrinsic vacancies of introduced trivalent dopant ions promote the delocalization of the intrinsic oxygen vacancies, while smaller tetravalent ions such as Zr4+ counteract this. Thus, doped cerium oxides with trivalent and tetravalent ions show almost no change in chemical expansion, as the opposite effects compensate each other.

elib-URL des Eintrags:https://elib.dlr.de/198399/
Dokumentart:Konferenzbeitrag (Vortrag)
Titel:Recent Results on Dopant influenced Chemical Expansion and Surface Alteration of Ceria
Autoren:
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iDORCID Put Code
Knoblauch, NicoleNicole.Knoblauch (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Lee, KangjaeKangjae.lee (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Alkan, GözdeGoezde.Alkan (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Mechnich, PeterPeter.Mechnich (at) dlr.dehttps://orcid.org/0000-0003-4689-8197146025203
Pein, MathiasMathias.Pein (at) dlr.dehttps://orcid.org/0000-0002-2796-1229146025204
Agrafiotis, ChristosChristos.Agrafiotis (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Roeb, MartinMartin.Roeb (at) dlr.deNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Datum:12 Oktober 2023
Referierte Publikation:Ja
Open Access:Nein
Gold Open Access:Nein
In SCOPUS:Nein
In ISI Web of Science:Nein
Status:veröffentlicht
Stichwörter:Ceria, Dilatometry, surface chemistry
Veranstaltungstitel:SolarPACES
Veranstaltungsort:Sydney
Veranstaltungsart:internationale Konferenz
Veranstaltungsbeginn:10 Oktober 2023
Veranstaltungsende:13 Oktober 2023
HGF - Forschungsbereich:Energie
HGF - Programm:Materialien und Technologien für die Energiewende
HGF - Programmthema:Chemische Energieträger
DLR - Schwerpunkt:Energie
DLR - Forschungsgebiet:E SW - Solar- und Windenergie
DLR - Teilgebiet (Projekt, Vorhaben):E - Solare Brennstoffe
Standort: Köln-Porz
Institute & Einrichtungen:Institut für Werkstoff-Forschung > Struktur- und Funktionskeramik
Institut für Future Fuels
Hinterlegt von: Knoblauch, Nicole
Hinterlegt am:06 Nov 2023 10:41
Letzte Änderung:24 Apr 2024 20:58

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