| 1. |
- Zhang, Wenhua, 1981-, et al.
(författare)
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A first-principles study of NO adsorption and oxidation on Au(111) surface
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:13, s. 134708-
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Tidskriftsartikel (refereegranskat)abstract
- Density functional theory and slab models are employed to study NO molecule adsorption and reaction on clean and atomic oxygen precovered Au(111) surfaces. While clean Au(111) surface is catalytically inert and can only weakly adsorb NO, an atomic oxygen precovered Au(111) surface is found to be very active to NO. On the clean surface, NO prefers to bond at the onefold on-top surface site with a tilted geometry. On 0.33 ML (monolayer) oxygen precovered surface NO reacts with chemisorbed oxygen to form chemisorbed NO2 by conquering a small energy barrier about 0.18 eV, and the desorption energy of NO 2 is 0.64 eV. On 1.0 ML oxygen coverage surface, no barrier is found while NO reacts with precovered oxygen. The desorption energy of NO2 is 0.03 eV. The desorption of NO2 is the rate determining step on both surfaces and the overall reaction barriers are 0.64 and 0.03 eV, respectively. The activation energies depend on the initial coverage of oxygen, which compare favorably with experiments on Au surface with different oxygen coverages.
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| 2. |
- Zhang, Wenhua, 1981-, et al.
(författare)
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Density Functional Study on the Mechanism of CO Oxidation with Activated Water on O/Au(111) Surface
- 2009
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Ingår i: Chinese Science Bulletin. - : Elsevier BV. - 1001-6538 .- 1861-9541 .- 2095-9273 .- 2095-9281. ; 54:11, s. 1973-1977
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Tidskriftsartikel (refereegranskat)abstract
- With density functional theory, the mechanism of water-enhanced CO oxidation on oxygen pre-covered Au (111) surface is theoretically studied. First, water is activated by the pre-covered oxygen atom and dissociates to OHads group. Then, OHads reacts with COads to form chemisorbed HOCOads. Finally, with the aid of water, HOCO ads dissociates to CO2. The whole process can be described as 1/2H2O ads + H2Oads + 1/2O ads + COads → H3Oads + CO 2, gas. One CO2 is formed with only 1/2 pre-covered oxygen atom. That is why more CO2 is observed when water is present on oxygen pre-covered Au (111) surface. Activation energy of each elementary step is low enough to allow the reaction to proceed at low temperature
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| 3. |
- Zhang, Wenhua, 1981-
(författare)
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First Principles Studies on Chemical and Electronic Structures of Adsorbates
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, we focus on theoretical study of adsorbates on metal and oxide surfaces that are important for surface chemistry and catalysis. Based on first principles calculations, the adsorption ofCO, NO, NO2, C4H6S2, C22H27SH and other molecules or radicals on nobel metal surfaces (gold and silver) are investigated. Also, NO oxidation on oxygen pre-covered Au(111)surface and CO oxidation on water-oxygen covered Au(111)surface aretheoretically studied. A new mechanism of water-enhanced COoxidation is proposed. As for oxide surfaces, we first investigatethe geometric, electronic and magnetic structures of FeO ultrathin film on Pt(111) surface. The experimentally observed scanning tunneling microscopy images are well reproduced for the first timewith our model. The adsorption and dissociation of water on rutileTiO2(110) surface are investigated by quantum molecular dynamics.By theoretical X-ray photoemission spectroscopy (XPS) calculations,the surface species are properly assigned. The same strategy has applied to the study of the phase transition of water covered reconstructed anatase TiO2(001) surface, from which two different phases are theoretically identified. The structure of graphene oxideis also studied by comparing experimental and theoretical XPS spectra. Based on the novel structures identified, a new cutmechanism of graphene oxide is proposed.
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