Characterization of Oxidation and Reduction of Pt鈥揜u and Pt鈥揜h鈥揜u Alloys by Atom Probe Tomography and Comparison with Pt鈥揜h

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• 作者：Tong Li ; Paul A. J. Bagot ; Emmanuelle A. Marquis ; S. C. Edman Tsang ; George D. W. Smith
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：August 23, 2012
• 年：2012
• 卷：116
• 期：33
• 页码：17633-17640
• 全文大小：432K
• 年卷期：v.116,no.33(August 23, 2012)
• ISSN：1932-7455

文摘

Pt-based alloys containing Rh and Ru are effective catalysts in a range of applications, including pollution control and low-temperature fuel cells. As the Pt group metals are generally rare and expensive, minimizing the loading of them while also increasing the efficiency of catalyst materials is a continual challenge in heterogeneous catalysis. A smart method to 鈥渘anoengineer鈥?the surface of the nanocatalyst particles would greatly aid this goal. In our study, the oxidation of a Pt鈥?.9 at. % Ru alloy between 773 and 973 K and the oxidation and oxidation/reduction behavior of a Pt鈥?3.9 at. % Rh鈥?.7 at. % Ru alloy at 873 K for various exposure times were studied using atom probe tomography. The surface of the Pt鈥揜u alloy is enriched with Ru after oxidation at 773 K, whereas it is depleted in Ru at 873 K, and at 973 K. The surface oxide layer vanishes at higher temperatures, leaving behind a Pt-rich surface. In the case of the Pt鈥揜h鈥揜u alloy, oxidation initiates from the grain boundaries, forming an oxide with a stoichiometry of MO₂. As the oxidation time increases, this oxide evolves into a two-phase nanostructure, involving a Rh-rich oxide phase (Rh, Ru)₂O₃ and a Ru-rich oxide phase (Ru, Rh)O₂. When this two-phase oxide is reduced in hydrogen at low temperatures, separate Rh-rich and Ru-rich nanoscale regions remain. This process could, therefore, be useful for synthesizing complex island structures on Pt鈥揜h鈥揜u nanoparticle catalysts.