Observation of oxygen vacancy filling under water vapor in ceramic proton conductors in situ with ambient pressure XPS
Küçük Resim Yok
Tarih
2013
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
The interaction of metal oxides with their ambient environment at elevated temperatures is of significant relevance for the functionality and operation of ceramic fuel cells, electrolyzers, and gas sensors. Proton conductivity in metal oxides is a subtle transport process which is based on formation of oxygen vacancies by cation doping and substitution and oxygen vacancy filling upon hydration in water vapor atmosphere. We have investigated the conductivity and electronic structure of the BaCeY-oxide proton conductor under realistic operation conditions from 373 to 593 K and water vapor pressures up to 200 mTorr in situ by combining ambient pressure X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. We provide element specific spectroscopic evidence that oxygen vacancies are filled by oxygen upon water exposure and partly oxidize Ce3+ and Y2+ toward Ce 4+ and Y3+. Moreover, the resonant valence band spectra of dry and hydrated samples show that oxygen ligand holes in the proximity of the Y dopant are by around 0.5 eV closer to the Fermi level than the corresponding hole states from Ce. Both hole states become substantially depleted upon hydration, while the proton conductivity sets on and increases systematically. Charge redistribution between lattice oxygen, Ce, and Y when BCY is exposed to water vapor at ambient and high temperature provides insight in the complex mechanism for proton incorporation in BCY. © 2013 American Chemical Society.
Açıklama
Anahtar Kelimeler
ambient pressure XPS, AP-XPS, impedance spectroscopy, in situ spectroscopy, oxygen vacancy, perovskite, proton conductor, proton diffusivity, resonant photoemission, valence band
Kaynak
Chemistry of Materials
WoS Q Değeri
Scopus Q Değeri
Q1
Cilt
25
Sayı
23
