Defect Chemistry of Oxide Nanomaterials with High Surface Area: Ordered Mesoporous Thin Films of the Oxygen Storage Catalyst CeO2鈥揨rO2

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• 作者：Pascal Hartmann ; Torsten Brezesinski ; Joachim Sann ; Andriy Lotnyk ; Jens-Peter Eufinger ; Lorenz Kienle ; J眉rgen Janek
• 刊名：ACS Nano
• 出版年：2013
• 出版时间：April 23, 2013
• 年：2013
• 卷：7
• 期：4
• 页码：2999-3013
• 全文大小：878K
• 年卷期：v.7,no.4(April 23, 2013)
• ISSN：1936-086X

文摘

Herein we report the electrical transport properties of a series of ordered mesoporous ceria鈥搝irconia (Ce_xZr_1鈥?i>xO₂, referred to as mp-CZO) thin films with both a cubic structure of (17 卤 2) nm diameter pores and nanocrystalline walls. Samples over the whole range of composition, including bare CeO₂ and ZrO₂, were fabricated by templating strategies using the large diblock copolymer KLE as the structure-directing agent. Both the nanoscale structure and the chemical composition of the mesoporous materials were analyzed by a combination of scanning and transmission electron microscopy, grazing incidence small-angle X-ray scattering, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The total conductivity as a function of the film composition, temperature, and oxygen partial pressure was measured using impedance spectroscopy. The mesoporous solid solutions of CeO₂鈥揨rO₂ prepared in this work showed a higher stability against thermal ripening than both binary oxides, making them ideal model systems to study both the charge transport properties and the oxygen storage at elevated temperatures. We find that the redox properties of nanocrystalline mp-CZO thin films differ significantly from those of bulk CZO materials reported in the literature and, therefore, propose a defect chemical model of surface regions.

Keywords:

oxygen storage; heterogeneous catalysis; nanocrystalline solids; nanoionics; mesoporous; self-assembly; thin films