The mechanism of N2O formation via the (NO)2 dimer:: A density functional theory study

被引:37
作者
Burch, R [1 ]
Daniells, ST [1 ]
Hu, P [1 ]
机构
[1] Queens Univ Belfast, Sch Chem, CenTACat, Belfast BT9 5AG, Antrim, North Ireland
关键词
D O I
10.1063/1.1767153
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Catalytic formation of N2O via a (NO)(2) intermediate was studied employing density functional theory with generalized gradient approximations. Dimer formation was not favored on Pt(111), in agreement with previous reports. On Pt(211) a variety of dimer structures were studied, including trans-(NO)(2) and cis-(NO)(2) configurations. A possible pathway involving (NO)(2) formation at the terrace near to a Pt step is identified as the possible mechanism for low-temperature N2O formation. The dimer is stabilized by bond formation between one O atom of the dimer and two Pt step atoms. The overall mechanism has a low barrier of approximately 0.32 eV. The mechanism is also put into the context of the overall NO+H-2 reaction. A consideration of the step-wise hydrogenation of O-(ads) from the step is also presented. Removal of O-(ads) from the step is significantly different from O-(ads) hydrogenation on Pt(111). The energetically favored structure at the transition state for OH(ads) formation has an activation energy of 0.63 eV. Further hydrogenation of OH(ads) has an activation energy of 0.80 eV. (C) 2004 American Institute of Physics.
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页码:2737 / 2745
页数:9
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