La-Dopant Location in La-Doped 纬-Al2O3 Nanoparticles Synthesized Using a Novel One-Pot Process

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• 作者：Stacey J. Smith ; Baiyu Huang ; Calvin H. Bartholomew ; Branton J. Campbell ; Juliana Boerio-Goates ; Brian F. Woodfield
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：November 5, 2015
• 年：2015
• 卷：119
• 期：44
• 页码：25053-25062
• 全文大小：789K
• ISSN：1932-7455

文摘

We have recently developed a 鈥渟olvent-deficient鈥?method of synthesizing high surface area 纬-Al₂O₃ nanoparticles that show promise for catalyst support applications. Here, we investigate doping the alumina with La³⁺ to stabilize the 纬 phase to higher temperatures. The one-pot method for synthesizing La-doped 纬-Al₂O₃ nanoparticles developed here has several advantages over conventional methods including requiring only 3 h instead of 3 days and wasting no lanthanum. TEM, X-ray PDF, and BET analyses as a function of calcination temperature show that the La stabilizes the 纬 phase by 100 掳C. In order to begin understanding the mechanism of stabilization, the location of the La³⁺ atoms in our doped 纬-Al₂O₃ nanoparticles is investigated via X-ray PDF and EXAFS analyses which indicate that the La dopant adsorbs as single, isolated atoms on the 纬-Al₂O₃ surface. As calcination temperature increases, the immediate oxygen coordination shell of the La becomes increasingly like La₂O₃ though an extended La₂O₃ lattice is not formed due to the sparse (3 wt %) concentration of La atoms. During the 纬-to-伪 transition, the La environment changes drastically to become more like LaAlO₃ than La₂O₃, suggesting that the La is enveloped by the alumina lattice during the 伪 phase transition though an extended LaAlO₃ lattice is not formed.