Studium katalytických vlastností systému oxid ceru - kov
System of cerium oxide and rhodium is used extensively in automotive emission control as a material suited for three-way catalysis. The prime for the activity of this catalyst is the oxidation state and a structure of CeOx. This study is focusing on CO oxidation and reactivity of the systems compose...
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| Format: | Dissertation |
| Language: | Czech |
| Published: |
2010
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| Online Access: | http://www.nusl.cz/ntk/nusl-286225 |
| Summary: | System of cerium oxide and rhodium is used extensively in automotive emission control as a material suited for three-way catalysis. The prime for the activity of this catalyst is the oxidation state and a structure of CeOx. This study is focusing on CO oxidation and reactivity of the systems composed of polycrystalline layers of cerium oxide prepared by magnetron sputtering which approach well the real catalysts with their chemical and structural properties. Rhodium was evaporated on various CeOx layers differing in the oxygen concentration. X-ray Photoelectron Spectroscopy (XPS) was used to characterize an electronic and chemical state of a surface. Its reactivity toward CO was observed by Temperature Programmed Desorption (TPD) and Molecular Beams (MB). During steady - state reactions of CO and O2 molecular beams in temperature interval of 300 K - 770 K, there were observed three reaction mechanisms of CO2. Through the developement of reactivity of a catalyst caused by changes of partial pressure of O2 and by using isotopic labeled 13C16O, we can distinguish contributions of separate mechanisms to the total yield of CO2 and suggest the process of reactions. Polycrystalline cerium oxide plays the kye role due to its ability to release and adopt oxygen and due to the facility of oxygen migration through the... |
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