In Situ TEM Study of Rh Particle Sintering for Three-Way Catalysts in High Temperatures

Catalysts

Yukihiro Shimizu¹  Makoto Nagata²  Hiroki Nakayama²  Hideki Abe³ 

[1] Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan;N.E. CHEMCAT Corporation, Numazu 410-0314, Japan;National Institute for Materials Science, Tsukuba 305-0044, Japan;

关键词: in situ TEM;    Rh sintering;    DFT calculation;    automotive catalyst;    SMSI (strong metal–support interaction);   

DOI  :  10.3390/catal11010019

来源: DOAJ

【 摘 要 】

One of the main factors in the deterioration of automobile three-way catalysts is the sintering of platinum group metals (PGMs). In this study, we used in situ tunneling electron microscopy (TEM) to examine the sintering of Rh particles as the temperature increases. Two types of environmental conditions were tested, namely, vacuum atmosphere with heating up to 1050 °C, and N₂ with/without 1% O₂ at 1 atm and up to 1000 °C. Under vacuum, Rh particles appeared to be immersed in ZrO₂. In contrast, at 1 atm N₂ with or without 1% O₂, the sintered Rh particles appeared spherical and not immersed in ZrO_2. The latter trend of Rh sintering resembles the actual engine-aged catalyst observed ex situ in this study. In the N₂ atmosphere, the sintering of support material (ZrO₂ or Y-ZrO₂) was first observed by in situ TEM, followed by Rh particle sintering. The Rh particle size was slightly smaller on Y-ZrO₂ compared to that on ZrO₂. To better understand these experimental results, density functional theory was used to calculate the systems’ junction energies, assuming three layers of Rh(111) 4 × 4 structures joined to the support material (ZrO₂ and Y-ZrO₂). The calculated energies were consistent with the in situ TEM observations in the N₂ atmosphere.

【 授权许可】

Unknown