TY - JOUR
T1 - In Situ TEM study of Rh particle sintering for three-way catalysts in high temperatures
AU - Nakayama, Hiroki
AU - Nagata, Makoto
AU - Abe, Hideki
AU - Shimizu, Yukihiro
N1 - Funding Information:
This work was supported by the European Commission through NanoCIS project (FP7-PEOPLE-2010-IRSES ref. 269279). One of the authors (S. Ullah) acknowledges Erasmus Mundus IDEAS Action-II for finantial support.
Publisher Copyright:
© 2020 by the authors. LicenseeMDPI, Basel, Switzerland.
PY - 2021/1
Y1 - 2021/1
N2 - 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 ZrO2. 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.
AB - 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 ZrO2. 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.
KW - Automotive catalyst
KW - DFT calculation
KW - In situ TEM
KW - Rh sintering
KW - SMSI (strong metalsupport interaction)
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U2 - 10.3390/catal11010019
DO - 10.3390/catal11010019
M3 - Article
AN - SCOPUS:85099209741
SN - 2073-4344
VL - 11
SP - 1
EP - 16
JO - Catalysts
JF - Catalysts
IS - 1
M1 - 19
ER -