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Adsorption of CO2 and H2 on Cu and Zn Micro-Cluster Surfaces Studied by Quantum Chemistry and Theory of Absolute Reaction Rates  [PDF]
Hiroaki Kuze, Shin’ichiro Okude
Open Journal of Physical Chemistry (OJPC) , 2011, DOI: 10.4236/ojpc.2011.13015
Abstract: Statistical mechanics and semi-empirical molecular orbital theory (PM6) are used to calculate the surface coverage of CO2 and H2 molecular species chemically adsorbed on the surface of Cu and Zn micro clusters. The calculation shows that CO2 is adsorbed well both on the surface of Cu and Zn micro clusters. Although H2 is adsorbed well on the surface of Zn micro clusters, H2 absorption on the surface of Cu micro clusters is much more limited in the pressure range of 20 - 100 atm and temperature range of 200 - 1000 K. Reaction rates are also estimated for some chemical adsorption process of H2 gas using theory of absolute reaction rates. It is found that the values of the reaction rate calculated in the present paper agree reasonably well with the experimental values.
Adsorption of H2 on MgO clusters studied by ab initio method

Chen Hong-Shan,Chen Hua-Jun,

物理学报 , 2011,
Abstract: Based on the most stable structures of the magic MgO clusters, the adsorption of H2 onto the rocksalt and hexagonal tube (MgO)9,12 is studied using first principal method. The results show that physical adsorption can be formed on Mg+q or O-q ions at different sites of the clusters. On the top of the Mg+q ions, H2 is adsorbed in the side-on manner and donates electrons to the ions. On the top of the O-q ions, H2 is adsorbed in the end-on manner and the molecule is polarized. The strength of the adsorption depends mainly on the location of the Mg/O ions, and the smaller the coordination number of the ions, the stronger the adsorption of H2 is. For the Mg/O ions with the same coordination number, the adsorption formed onto the Mg+q is stronger. According to the Mg or O ions and their locations, the adsorption energy ranges from 0.03 eV to 0.08 eV.
The Unity of Chemistry and Physics: Absolute Reaction Rate Theory
Hinne Hettema
Hyle : International Journal for Philosophy of Chemistry , 2012,
Abstract: Henry Eyring's absolute rate theory explains the size of chemical reaction rate constants in terms of thermodynamics, statistical mechanics, and quantum chemistry. In addition it uses a number of unique concepts such as the 'transition state'. A key feature of the theory is that the explanation it provides relies on the comparison of reaction rate constant expressions derived from these individual theories. In this paper, the example is used to develop a naturalized notion of reduction and the unity of science. This characterization provides the necessary clues to the sort of inter-theoretic linkages that are present in the theory of reaction rates. The overall theory is then further characterized as a theory network, establishing connections between non-reductive notions of inter-theory connections. This characterization also sheds new light on the unity of science.
?Dissociation of H2 on Al 7 cluster studied by ab initio calculations?

Li Wen-Jie,Yang Hui-Hui,Chen Hong-Shan,

物理学报 , 2013,
Abstract: With the accurate ab initio method, the adsorption and dissociation process of H2 molecule on Al7- cluster anion are investigated. The stable structures of molecular adsorption and dissociative adsorption are confirmed. The photoelectron spectra of different structures are further analyzed. The calculations indicate that the adsorption of H2 on Al7- is weak physical adsorption with the adsorption energy about 0.02 eV. The investigation of the dissociation process shows that the energy barrier of dissociation is about 0.75 eV. The densities of states of the Al7- cluster and the dissociative adsorption complex Al7H2- are in good agreement with those obtained by the photoelectron spectroscopy. It suggests that H2 can be dissociated when it is absorbed on Al7- anions produced by laser ablation.
Adsorption and grafting on colloidal interfaces studied by scattering techniques  [PDF]
Julian Oberdisse
Physics , 2007, DOI: 10.1016/j.cocis.2006.11.001
Abstract: The adsorption of polymer and surfactant molecules onto colloidal particles or droplets in solution can be characterized non-destructively by scattering techniques. In a first part, the general framework of Dynamic Light Scattering, Small Angle Neutron and X-ray Scattering for the determination of the structure of adsorbed layers, and namely of the density profile, is presented. We then review recent studies of layers of the model polymer poly(ethylene oxide), as homopolymer or part of a block copolymer. In this field, scattering with contrast variation has been shown to be a powerful tool to obtain a detailed description of the layer structure. Adsorption of chemically more complex systems, including polyelectrolytes, polymer complexes, grafted chains and biomacromolecules are also discussed in this review, as well as surfactant adsorption.
Water desorption and re-adsorption on epitaxial graphene studied by SPM  [PDF]
Tim L. Burnett,Jack Patten,Olga Kazakova
Physics , 2012,
Abstract: We demonstrate the temperature-mediated and completely reversible process of desorption-readsorption of water on a few layers of epitaxial graphene on a 4H-SiC(0001) substrate. We show that under ambient conditions water forms solid structures on top of the second and third layers of graphene. In the case of strained or highly defective graphene domains, these features produce strongly correlated and reproducible patterns, implying importance of the underlying defects for the initial stages of water adsorption. Hydrophobicity increases with number of graphene layers. Evolution of the water layer as a function of temperature is accompanied by a significant (two-fold) change of the absolute surface potential difference between one and two layers of graphene. In situ observation of water evolution during heating also potentially provides a direct method for measurement of the heat adsorption on the nanoscale.
Stability, Adsorption and Diffusion of CH4, CO2 and H2 in Clathrate Hydrates  [PDF]
Guillermo Román-Pérez,Mohammed Moiaed,Jose M. Soler,Felix Yndurain
Physics , 2010, DOI: 10.1103/PhysRevLett.105.145901
Abstract: We present a study of the adsorption and diffusion of CH4, CO2 and H2 molecules in clathrate hydrates using ab initio van der Waals density functional formalism [Dion et al. Phys. Rev. Lett. 92, 246401 (2004)]. We find that the adsorption energy is dominated by van der Waals interactions and that, without them, gas hydrates would not be stable. We calculate the maximum adsorption capacity as well as the maximum hydrocarbon size that can be adsorbed.The relaxation of the host lattice is essential for a good description of the diffusion activation energies, which are estimated to be of the order of 0.2, 0.4, and 1.0 eV for H2, CO2, and CH4, respectively.
A computational investigation of H2 adsorption and dissociation on Au nanoparticles supported on TiO2 surface  [PDF]
Andrey Lyalin,Tetsuya Taketsugu
Physics , 2011, DOI: 10.1039/c1fd00013f
Abstract: The specific role played by small gold nanoparticles supported on the rutile TiO2(110) surface in the processes of adsorption and dissociation of H2 is discussed. It is demonstrated that the molecular and dissociative adsorption of H2 on Au_n clusters containing n = 1, 2, 8 and 20 atoms depends on cluster size, geometry structure, cluster flexibility and the interaction with the support material. Rutile TiO2(110) support energetically promotes H2 dissociation on gold clusters. It is demonstrated that the active sites towards H2 dissociation are located at corners and edges on the surface of the gold nanoparticle in the vicinity of the support. The low coordinated oxygen atoms on the TiO2(110) surface play a crucial role for H2 dissociation. Therefore the catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support.
The chemistry of vibrationally excited H2 in the interstellar medium  [PDF]
M. Agundez,J. R. Goicoechea,J. Cernicharo,A. Faure,E. Roueff
Physics , 2010, DOI: 10.1088/0004-637X/713/1/662
Abstract: The internal energy available in vibrationally excited H2 molecules can be used to overcome or diminish the activation barrier of various chemical reactions of interest for molecular astrophysics. In this article we investigate in detail the impact on the chemical composition of interstellar clouds of the reactions of vibrationally excited H2 with C+, He+, O, OH, and CN, based on the available chemical kinetics data. It is found that the reaction of H2 (v>0) and C+ has a profound impact on the abundances of some molecules, especially CH+, which is a direct product and is readily formed in astronomical regions with fractional abundances of vibrationally excited H2, relative to ground state H2, in excess of 10^(-6), independently of whether the gas is hot or not. The effects of these reactions on the chemical composition of the diffuse clouds zeta Oph and HD 34078, the dense PDR Orion Bar, the planetary nebula NGC 7027, and the circumstellar disk around the B9 star HD 176386 are investigated through PDR models. We find that formation of CH+ is especially favored in dense and highly FUV illuminated regions such as the Orion Bar and the planetary nebula NGC 7027, where column densities in excess of 10^(13) cm^(-2) are predicted. In diffuse clouds, however, this mechanism is found to be not efficient enough to form CH+ with a column density close to the values derived from astronomical observations.
Protein Adsorption to Surface Chemistry and Crystal Structure Modification of Titanium Surfaces  [PDF]
Ryo Jimbo,Mikael Ivarsson,Anita Koskela,Young-Taeg Sul
Journal of Oral & Maxillofacial Research , 2010,
Abstract: Objectives: To observe the early adsorption of extracellular matrix and blood plasma proteins to magnesium-incorporated titanium oxide surfaces, which has shown superior bone response in animal models.Material and Methods: Commercially pure titanium discs were blasted with titanium dioxide (TiO2) particles (control), and for the test group, TiO2 blasted discs were further processed with a micro-arc oxidation method (test). Surface morphology was investigated by scanning electron microscopy, surface topography by optic interferometry, characterization by X-ray photoelectron spectroscopy (XPS), and by X-ray diffraction (XRD) analysis. The adsorption of 3 different proteins (fibronectin, albumin, and collagen type I) was investigated by an immunoblotting technique.Results: The test surface showed a porous structure, whereas the control surface showed a typical TiO2 blasted structure. XPS data revealed magnesium-incorporation to the anodic oxide film of the surface. There was no difference in surface roughness between the control and test surfaces. For the protein adsorption test, the amount of albumin was significantly higher on the control surface whereas the amount of fibronectin was significantly higher on the test surface. Although there was no significant difference, the test surface had a tendency to adsorb more collagen type I.Conclusions: The magnesium-incorporated anodized surface showed significantly higher fibronectin adsorption and lower albumin adsorption than the blasted surface. These results may be one of the reasons for the excellent bone response previously observed in animal studies.
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