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| 2. |
- Li, Zhenyu, et al.
(author)
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How Graphene is Cut upon Oxidation?
- 2009
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:18, s. 6320-6321
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Journal article (peer-reviewed)abstract
- Our first principles calculations reveal that an oxidative cut of graphene is realized by forming epoxy and then carbonyl pairs. Direct formation of a carbonyl pair to tear graphene up from an edge position is not favorable in energy. This atomic picture is valuable for developing effective means of graphene manipulation. The proposed epoxy pairs may be related to some long puzzling experimental observations on graphene oxide.
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| 3. |
- Zhang, Wenhua, 1981-, et al.
(author)
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A first-principles study of NO adsorption and oxidation on Au(111) surface
- 2008
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:13, s. 134708-
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Journal article (peer-reviewed)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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| 4. |
- Zhang, Wenhua, 1981-, et al.
(author)
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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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In: Chinese Science Bulletin. - : Elsevier BV. - 1001-6538 .- 1861-9541 .- 2095-9273 .- 2095-9281. ; 54:11, s. 1973-1977
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Journal article (peer-reviewed)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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| 5. |
- Zhang, Wenhua, et al.
(author)
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First Principles Study on the Geometric and Electronic Structures of the FeO/Pt(111) Surface
- 2009
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:19, s. 8302-8305
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Journal article (peer-reviewed)abstract
- The geometric, electronic, and magnetic properties of the FeO monolayer on a Pt(111) surface are investigated by first principles calculations. Generally, antiferromagnetic (AFM) structures are more stable than that of the ferromagnetic one. On the basis of a specific AFM structure, the long puzzling scanning tunneling microscopy (STM) experimental observations can be well explained. In this AFM model, the Fe-O layer distance at the fee region is larger than the hcp region, in contrast to previous theoretical results. The STM images at the field-emission regime are explained by local surface potential.
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| 6. |
- Zhang, Wenhua, et al.
(author)
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Oxidation states of graphene : Insights from computational spectroscopy
- 2009
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:24
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Journal article (peer-reviewed)abstract
- When it is oxidized, graphite can be easily exfoliated forming graphene oxide (GO). GO is a critical intermediate for massive production of graphene, and it is also an important material with various application potentials. With many different oxidation species randomly distributed on the basal plane, GO has a complicated nonstoichiometric atomic structure that is still not well understood in spite of intensive studies involving many experimental techniques. Controversies often exist in experimental data interpretation. We report here a first principles study on binding energy of carbon 1s orbital in GO. The calculated results can be well used to interpret experimental x-ray photoelectron spectroscopy (XPS) data and provide a unified spectral assignment. Based on the first principles understanding of XPS, a GO structure model containing new oxidation species epoxy pair and epoxy-hydroxy pair is proposed. Our results demonstrate that first principles computational spectroscopy provides a powerful means to investigate GO structure.
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| 7. |
- Zhang, Wenhua, et al.
(author)
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Theoretical Study of X-ray PhotoemissionSpectra of Graphene Oxide
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Other publication (other academic/artistic)abstract
- Chemical structure of graphene oxide is complicated by the presence of many different oxidation species. We report here a density functional theory study on binding energy of carbon 1s at different oxidation environments on a graphene oxide sheet. It is shown that the calculated results can be wellused to interpret experimental X-ray photoemission spectra of different research groups and provide united spectral assignments. New species that are important for understanding cut mechanisms of graphene oxide have been identified.
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