First-Principles Studies of the Activation of Oxygen Molecule and Its Role in Partial Oxidation of Methane on Boron-Doped Single-Walled Carbon Nanotubes
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- 作者：Bo Li ; Dangsheng Su
- 刊名：Journal of Physical Chemistry C
- 出版年：2013
- 出版时间：August 29, 2013
- 年：2013
- 卷：117
- 期：34
- 页码：17485-17492
- 全文大小：470K
- 年卷期：v.117,no.34(August 29, 2013)
- ISSN：1932-7455
文摘
The nanostructured carbon materials have been widely tested as catalyst in a number of chemical reactions. The oxygen functional groups on nanostructured carbon catalyst are believed to be the active sites, for example, in the oxidative dehydrogenation reaction of hydrocarbons. However, the doping is one of the effective ways to tune the properties of nanostructured carbon materials. It will be important to examine the effect of doping on the catalytic properties of oxygen molecule on nanostructured carbon materials. In current work, the dissociation of the oxygen molecule on the boron-doped single-walled carbon nanotube (BSWCNT) and their catalytic properties in the partial oxidation of methane to formaldehyde are investigated by using first-principles calculations. Both defect-free BSWCNT and defective BSWCNT with a monovacancy are studied, and the comparisons between them are made. BSWCNT demonstrates a good ability for the dissociation of oxygen molecule. The favorable binding sites for the dissociated oxygen molecule are the positively charged atoms on BSWCNTs because oxygen molecule itself is negatively charged by obtaining electrons from carbons. The barrier of the oxygen dissociation is 0.88 and 0.12 eV, respectively, for defect-free and defective BSWCNTs. Furthermore, the dissociated oxygen molecule on BSWCNT exhibits the ability to break the C鈥揌 bond in methane molecule and the dissociated fragments (CH<sub>3sub> and H) bind on the oxygens on BSWCNTs. The C鈥揌 bond breaking results from the charge abstraction from hydrogen in methane molecule by BSWCNT. The minimum energy path looks similar for both defect-free and defective BSWCNTs, which involves a methyl radical translation after transition state. However, the barrier is smaller by 0.5 eV on defective BSWCNTs and comparable with other catalysts for methane activation. The CH<sub>3sub>O on BSWCNT can be further converted to the formaldehyde with the calculated barrier of 1.37 eV. The current study indicates that the boron doping is a promising effective way to optimize the catalytic properties of carbon nanotube catalyst.