Abstract
Methane activation is usually assumed to take place on top of metal surfaces or metal clusters. It can also occur at the metal-support interface in metal-supported catalysts with reducible oxides, such as CeO 2 . In the present work, we exploit density functional theory with an additional Hubbard-like parameter (DFT + U) to calculate the activation of methane at an O site interfacing a Ni 4 metal cluster on a support, CeO 2 (111) surface. Two reaction routes, namely, radical and nonradical routes, are taken into account. We show that the nonradical route is favored with an apparent activation energy of 18.1 kcal/mol, which is lower than that for the radical route by 15.0 kcal/mol. In the nonradical route, the formation of a four-centered transition-state structure is observed while a C-H bond of methane is being cleaved to form an OH moiety and a CH 3 fragment that is being bound to the interfacial Ni atom. It is also found that the interfacial O atoms are out of the CeO 2 surface plane with Ce-O bond distances being much longer than those in the crystalline bulk CeO 2 , which allows them to be easily reduced, and hence, the interfacial O atoms become more reactive toward methane, as compared to the surface O atoms. The interactions between Ni 4 cluster and the CeO 2 (111) surface result in the reduction of two Ce 4+ ions to Ce 3+ , improving the reducibility of the interfacial O atoms. This should be an important key to the facile methane activation.
| Original language | English |
|---|---|
| Pages (from-to) | 9788-9798 |
| Number of pages | 11 |
| Journal | Journal of Physical Chemistry C |
| Volume | 123 |
| Issue number | 15 |
| DOIs | |
| Publication status | Published - Apr 18 2019 |
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All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Energy(all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
Cite this
Methane Activation at the Metal-Support Interface of Ni 4 -CeO 2 (111) Catalyst : A Theoretical Study. / Singha, Rajib Kumar; Tsuji, Yuta; Mahyuddin, Muhammad Haris; Yoshizawa, Kazunari.
In: Journal of Physical Chemistry C, Vol. 123, No. 15, 18.04.2019, p. 9788-9798.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Methane Activation at the Metal-Support Interface of Ni 4 -CeO 2 (111) Catalyst
T2 - A Theoretical Study
AU - Singha, Rajib Kumar
AU - Tsuji, Yuta
AU - Mahyuddin, Muhammad Haris
AU - Yoshizawa, Kazunari
PY - 2019/4/18
Y1 - 2019/4/18
N2 - Methane activation is usually assumed to take place on top of metal surfaces or metal clusters. It can also occur at the metal-support interface in metal-supported catalysts with reducible oxides, such as CeO 2 . In the present work, we exploit density functional theory with an additional Hubbard-like parameter (DFT + U) to calculate the activation of methane at an O site interfacing a Ni 4 metal cluster on a support, CeO 2 (111) surface. Two reaction routes, namely, radical and nonradical routes, are taken into account. We show that the nonradical route is favored with an apparent activation energy of 18.1 kcal/mol, which is lower than that for the radical route by 15.0 kcal/mol. In the nonradical route, the formation of a four-centered transition-state structure is observed while a C-H bond of methane is being cleaved to form an OH moiety and a CH 3 fragment that is being bound to the interfacial Ni atom. It is also found that the interfacial O atoms are out of the CeO 2 surface plane with Ce-O bond distances being much longer than those in the crystalline bulk CeO 2 , which allows them to be easily reduced, and hence, the interfacial O atoms become more reactive toward methane, as compared to the surface O atoms. The interactions between Ni 4 cluster and the CeO 2 (111) surface result in the reduction of two Ce 4+ ions to Ce 3+ , improving the reducibility of the interfacial O atoms. This should be an important key to the facile methane activation.
AB - Methane activation is usually assumed to take place on top of metal surfaces or metal clusters. It can also occur at the metal-support interface in metal-supported catalysts with reducible oxides, such as CeO 2 . In the present work, we exploit density functional theory with an additional Hubbard-like parameter (DFT + U) to calculate the activation of methane at an O site interfacing a Ni 4 metal cluster on a support, CeO 2 (111) surface. Two reaction routes, namely, radical and nonradical routes, are taken into account. We show that the nonradical route is favored with an apparent activation energy of 18.1 kcal/mol, which is lower than that for the radical route by 15.0 kcal/mol. In the nonradical route, the formation of a four-centered transition-state structure is observed while a C-H bond of methane is being cleaved to form an OH moiety and a CH 3 fragment that is being bound to the interfacial Ni atom. It is also found that the interfacial O atoms are out of the CeO 2 surface plane with Ce-O bond distances being much longer than those in the crystalline bulk CeO 2 , which allows them to be easily reduced, and hence, the interfacial O atoms become more reactive toward methane, as compared to the surface O atoms. The interactions between Ni 4 cluster and the CeO 2 (111) surface result in the reduction of two Ce 4+ ions to Ce 3+ , improving the reducibility of the interfacial O atoms. This should be an important key to the facile methane activation.
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U2 - 10.1021/acs.jpcc.8b11973
DO - 10.1021/acs.jpcc.8b11973
M3 - Article
VL - 123
SP - 9788
EP - 9798
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 15
ER -