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A surface science study of model automotive emissions control catalysis: Oxygen storage properties of ceria thin films.

机译:模型汽车排放控制催化的表面科学研究:二氧化铈薄膜的储氧性能。

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Ceria and zirconia are important oxide components of the three-way catalyst (TWC) for automotive emissions control. Simultaneous conversion of harmful exhaust pollutants is enhanced by ceria's ability to store and release oxygen to maintain conditions within a narrow operating window of air-to-fuel ratios. Zirconia increases ceria's effectiveness for oxygen storage, yet a fundamental understanding of this favorable interaction is still lacking. In this thesis, surface-sensitive spectroscopic techniques were used to characterize interactions at ceria-zirconia interfaces and their effect on the activity of model emissions control catalysts. The structure-activity relationships and oxygen transport properties of ceria-based samples were studied primarily using temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Thermal desorption of CO and conversion to CO2 were used as chemical probes of the oxidation and reduction of ceria. NO and CH3OH reactivity on ceria surfaces was used to monitor oxygen vacancy (Ce3+) sites. XPS was used to directly measure the oxidation state of cerium cations. These chemical and spectroscopic probes demonstrated that interactions at the ceria-zirconia interface are responsible for an enhanced reducibility, and therefore enhanced oxygen transport, throughout the ceria layer. This enhanced reducibility results in an increased oxygen storage capacity in the TWC for emissions control.
机译:二氧化铈和氧化锆是三元催化剂(TWC)中重要的氧化物成分,可用于控制汽车排放。氧化铈储存和释放氧气的能力增强了有害废气污染物的同时转化,以在狭窄的空燃比运行窗口内维持条件。氧化锆提高了二氧化铈的储氧效率,但仍缺乏对这种有利相互作用的基本了解。本文采用表面敏感光谱技术表征了二氧化铈-氧化锆界面的相互作用及其对模型排放控制催化剂活性的影响。主要使用程序升温脱附(TPD)和X射线光电子能谱(XPS)研究了基于二氧化铈的样品的结构活性关系和氧传输性质。 CO的热脱附和转化为CO 2 被用作氧化铈和氧化铈的化学探针。用二氧化铈表面的NO和CH 3 OH反应性监测氧空位(Ce 3 + )的位置。 XPS用于直接测量铈阳离子的氧化态。这些化学和光谱探针表明,在二氧化铈-氧化锆界面处的相互作用导致整个二氧化铈层的还原性增强,从而增强了氧气的输送。这种增强的可还原性导致TWC中用于排放控制的氧气存储容量增加。

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