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Correlation between surface potentials and surface oxygen exchange coefficents of CeO2

CeO2表面电位与表面氧交换系数的相关性

基本信息

批准号：
267908922
负责人：
Professor Roger De Souza, Ph.D.
金额：
--
依托单位：
Lehrstuhl für Physikalische Chemie I
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/267908922?language=en
关键词：
Correlation between surface potentials oxygen

项目摘要

The aim of this proposal is to investigate the possible correlation between the surface Fermi level position, ionization potential, and work function and the oxygen surface exchange rate of the prototypical oxygen-ion conductor, CeO2. As the energy levels of adsorbed oxygen species (relative to the band edges) are expected to depend directly on the work function of the substrate, they govern whether electron transfer to the adsorbed species, most likely a rate determining step, is possible or not. To examine the possible correlation, the work function of CeO2 will be determined systematically as a function of doping and oxygen partial pressure for various surface orientations and terminations. Differently doped polycrystalline and epitaxial thin CeO2 films will be prepared by magnetron sputtering for this purpose. The surface chemical composition and the surface potentials will then be determined by means of photoelectron spectroscopy without breaking vacuum conditions. The variation of surface potentials will be established during and after deposition through variation of deposition conditions and post-deposition oxidation and reduction treatments. The oxygen surface exchange rate will be investigated on identically prepared thin films as well as on sintered ceramic specimens by means of 18O tracer exchange measurements with secondary ion mass spectrometry as well as with conductivity relaxation experiments. The conditions for exchange will be set analogously to those established during work function analysis.

这个建议的目的是调查的表面费米能级的位置，电离势，和功函数和氧表面交换率的原型氧离子导体，CeO2之间的可能的相关性。由于吸附的氧物质的能级（相对于能带边缘）预计直接取决于衬底的功函数，它们决定电子转移到吸附的物质，最有可能的速率决定步骤，是否是可能的。为了研究可能的相关性，CeO2的功函数将被系统地确定为各种表面取向和终端的掺杂和氧分压的函数。采用磁控溅射法制备了CeO_2多晶外延薄膜。然后，在不破坏真空条件的情况下，通过光电子能谱法确定表面化学组成和表面电势。通过改变沉积条件和沉积后的氧化和还原处理，在沉积期间和之后建立表面电位的变化。氧气的表面交换率将研究同样制备的薄膜，以及烧结陶瓷试样通过18O示踪剂交换测量与二次离子质谱法，以及与电导率弛豫实验。交换条件的设定将类似于功函数分析期间设定的条件。