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A Space‐Charge Treatment of the Increased Concentration of Reactive Species at the Surface of a Ceria Solid Solution
Author(s) -
Zurhelle Alexander F.,
Tong Xiaorui,
Klein Andreas,
Mebane David S.,
De Souza Roger A.
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201708118
Subject(s) - x ray photoelectron spectroscopy , space charge , oxide , surface charge , chemistry , charge (physics) , catalysis , depletion region , analytical chemistry (journal) , chemical physics , materials science , chemical engineering , nanotechnology , layer (electronics) , physics , electron , quantum mechanics , organic chemistry , engineering
A space‐charge theory applicable to concentrated solid solutions (Poisson–Cahn theory) was applied to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X‐ray photoelectron spectroscopy (XPS) for the concentration of Ce 3+ (the reactive species) at the surface of the oxide catalyst Ce 0.8 Sm 0.2 O 1.9 . In contrast to previous theoretical treatments, these calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space‐charge zone. The high space‐charge potential that develops at the surface (>0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the space‐charge layer. This approach emphasizes the need to take into account defect interactions and to allow deviations from local charge neutrality when considering the surfaces of oxide catalysts.