Stability of Platinum Nanoparticles Supported on SiO2/Si(111): A High-Pressure X-ray Photoelectron Spectroscopy Study
详细信息 查看全文
- 作者：Soeren Porsgaard ; Lindsay R. Merte ; Luis K. Ono ; Farzad Behafarid ; Jeronimo Matos ; Stig Helveg ; Miquel Salmeron ; Beatriz Roldan Cuenya ; Flemming Besenbacher
- 刊名：ACS Nano
- 出版年：2012
- 出版时间：December 21, 2012
- 年：2012
- 卷：6
- 期：12
- 页码：10743-10749
- 全文大小：476K
- 年卷期：v.6,no.12(December 21, 2012)
- ISSN：1936-086X
文摘
The stability of Pt nanoparticles (NPs) supported on ultrathin SiO2 films on Si(111) was investigated in situ under H2 and O2 (0.5 Torr) by high-pressure X-ray photoelectron spectroscopy (HP-XPS) and ex situ by atomic force microscopy (AFM). No indication of sintering was observed up to 600 掳C in both reducing and oxidizing environments for size-selected Pt NPs synthesized by inverse micelle encapsulation. However, HP-XPS revealed a competing effect of volatile PtOx desorption from the Pt NPs (2 and 4 nm NP sizes) at temperatures above 450 掳C in the presence of 0.5 Torr of O2. Under oxidizing conditions, the entire NPs were oxidized, although with no indication of a PtO2 phase, with XPS binding energies better matching PtO. The stability of catalytic NPs in hydrogenation and oxidation reactions is of great importance due to the strong structure sensitivity observed in a number of catalytic processes of industrial relevance. An optimum must be found between the maximization of the surface active sites and metal loading (i.e., minimization of the NP size), combined with the maximization of their stability, which, as it will be shown here, is strongly dependent on the reaction environment.