催化作用
材料科学
氧化还原
拉曼光谱
钌
X射线光电子能谱
钙钛矿(结构)
氧化物
氧烷
程序升温还原
无机化学
光谱学
金属
分析化学(期刊)
化学工程
化学
结晶学
冶金
生物化学
物理
色谱法
量子力学
光学
工程类
作者
Yu Wang,Jaime Gallego,Wei Wang,Phillip Timmer,Min Ding,Alexander Spriewald Luciano,Tim Weber,Lorena Glatthaar,Yanglong Guo,Bernd M. Smarsly,Herbert Over
出处
期刊:Chinese Journal of Catalysis
[China Science Publishing & Media Ltd.]
日期:2023-11-01
卷期号:54: 250-264
标识
DOI:10.1016/s1872-2067(23)64547-4
摘要
The exsolution process enables to produce and control the formation of stable and catalytically active nano particles via reductive extraction of uniformly incorporated precious metal ions from a solid oxide solution. Here we consider the simple and stable perovskite LaFeO3 (LFO) where 10% of Fe on B sites are substituted by ruthenium (LFRO). Hydrogen reduction of LFRO at 800 °C leads to the formation of socketed ruthenium particles whose low-temperature activity in the total propane oxidation reaction at 210 °C is substantially lower than that of the original LFRO. Upon increasing the reaction temperature once to 400 °C, the exsolved catalyst undergoes self-activation so that the activity at 210 °C turns out to be five times higher than that of the original LFRO. High-resolution transmission electron microscopy and nanometer-resolved element mapping, together with averaging characterization methods, including X-ray diffraction and X-ray photoelectron spectroscopy, Raman spectroscopy, and diffuse infrared spectroscopy, unveil that after reduction at 800 °C the exsolved Ru particles are slightly alloyed with Fe and encapsulated by an inert and protecting LaOx layer. Mild oxidative treatment at 400 °C leads to the removal of the conforming LaOx layer, while the uncovered RuFe alloy particle transforms to catalytically active oxidic Ru species, with no indication of a separate FeOx phase. We exemplify with our case study of LaFe0.9Ru0.1O3 that careful redox treatment enables to control the exsolution process and to avoid deactivation. This may be of importance for the whole class of exsolvable materials.
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