X-ray absorption near-edge spectroscopy investigation of the oxidation state of Pd species in nanoporous SnO2 gas sensors for methane detection
| Autor: | Claus-Dieter Kohl, Michael Tiemann, Th. Wagner, Marco Bauer, Tilman Sauerwald |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Nanoporous
Inorganic chemistry Metals and Alloys Analytical chemistry chemistry.chemical_element Surfaces and Interfaces Nitrogen XANES Methane Surfaces Coatings and Films Electronic Optical and Magnetic Materials chemistry.chemical_compound chemistry Oxidation state Materials Chemistry Spectroscopy Absorption (electromagnetic radiation) Palladium |
| Zdroj: | Thin Solid Films. 520:909-912 |
| ISSN: | 0040-6090 |
| Popis: | We report the correlation of the aging of Pd-doped SnO 2 methane sensors with the change of the oxidation state of Pd. Mesoporous SnO 2 doped with palladium species was prepared and exposed to different gas mixtures at high temperature (600 °C) to simulate long term usage. After each exposure step a fraction of the sample was cooled down to “freeze” the current oxidation state of Pd which was then analyzed by X-ray Absorption Near-Edge Spectroscopy (XANES) using the 'white line' (i.e. the absorption peak corresponding to the transition from the 2p 3/2 core level to unoccupied 4 d states) intensity of the L(III) edge as a probe for the oxidation state. The Pd oxidation state correlates with the response of the resistive SnO 2 sensor to methane gas, as determined by measuring the gas response to different concentrations of methane. Samples treated with 5000 ppm methane in air show a significant reduction of Pd(II) to Pd(0), depending clearly on the carrier gas (synthetic air, pure nitrogen) and on the temperature (600 °C vs. 300 °C). |
| Databáze: | OpenAIRE |
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