Rutger A. van Santen

University of Oxford, Oxford, England, United Kingdom

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Publications (709)2489.56 Total impact

  • Bartłomiej Maciej Szyja, Rutger A van Santen
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    ABSTRACT: A computational study is presented of the cooperative effect of a small four atom Co oxide cluster supported on the TiO2 anatase (100) surface in the electrochemical water splitting reaction. Results have been obtained including explicit solvent water molecules by means of Car-Parrinello MD simulations. Reaction steps in the catalytic cycle determined involve the formation of TiO2 surface hydroxyl groups as well as elementary reaction steps on the Co oxide cluster. Essential is the observation of O-O bond formation at the inter-phase of Co oxide particle and TiO2 support.
    Physical Chemistry Chemical Physics 02/2015; DOI:10.1039/C5CP00196J · 4.20 Impact Factor
  • Xue-Qing Zhang, Rutger A. van Santen, Emiel J. M. Hensen
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    ABSTRACT: A reactive force field has been developed that is used in molecular dynamics (MD) studies of the surface transformation of the cobalt (0001) surface induced by an overlayer of adsorbed carbon atoms. Significant surface reconstruction is observed with movement of the Co atoms upward and part of the C atoms to positions below the surface. In a particular C ad atom coverage regime step edge type surface sites are formed, which can dissociate adsorbed CO with a low activation energy barrier. A driving force for the surface transformation is the preference of C adatoms to adsorb in 5- or 6-fold coordinated sites and the increasing strain in the surface because of the changes in surface metal atom-metal atom bond distances with the increasing surface overlayer concentration. The process is found to depend on the nanosize dimension of the surface covered with carbon. When this surface is an overlayer on top of a vacant Co surface, it can reduce stress by displacement of the Co atoms to unoccupied surface positions and the popping up process of Co atom does not occur. This explains why small nanoparticles will not reconstruct by popping up of Co atoms and do not create CO dissociation active sites even when covered with a substantial overlayer of C atoms.Keywords: catalysis; surface reconstruction; reactive force field; molecular dynamics; size dependence; step-edge sites
    ACS Catalysis 02/2015; 5(2):596-601. DOI:10.1021/cs501484c · 7.57 Impact Factor
  • Source
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    ABSTRACT: The target of our study is to approximate numerically and, in some particular physically relevant cases, also analytically, the residence time of particles undergoing an asymmetric simple exclusion dynamics on a stripe. The source of asymmetry is twofold: (i) the choice of boundary conditions (different reservoir levels) and (ii) the strong anisotropy from a nonlinear drift with prescribed directionality. We focus on the effect of the choice of anisotropy in the flux on the asymptotic behavior of the residence time with respect to the length of the stripe. The topic is relevant for situations occurring in pedestrian flows or biological transport in crowded environments, where lateral displacements of the particles occur predominantly affecting therefore in an essentially way the efficiency of the overall transport mechanism.
  • Rutger A. van Santen
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    ABSTRACT: Review: aspects of computational chemistry as well as kinetics and physical state of the reactive catalyst, 22 refs.
    ChemInform 11/2014; 45(46). DOI:10.1002/chin.201446297
  • John M. Brown, Andreas Pfaltz, Rutger A. van Santen
    ChemInform 11/2014; 45(44). DOI:10.1002/chin.201444292
  • Ivo A. W. Filot, Rutger A. van Santen, Emiel J. M. Hensen
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    ABSTRACT: Microkinetics simulations are presented based on DFT-determined elementary reaction steps of the Fischer–Tropsch (FT) reaction. The formation of long-chain hydrocarbons occurs on stepped Ru surfaces with CH as the inserting monomer, whereas planar Ru only produces methane because of slow CO activation. By varying the metal–carbon and metal–oxygen interaction energy, three reactivity regimes are identified with rates being controlled by CO dissociation, chain-growth termination, or water removal. Predicted surface coverages are dominated by CO, C, or O, respectively. Optimum FT performance occurs at the interphase of the regimes of limited CO dissociation and chain-growth termination. Current FT catalysts are suboptimal, as they are limited by CO activation and/or O removal.
    Angewandte Chemie International Edition 08/2014; 126(47). DOI:10.1002/anie.201406521 · 11.34 Impact Factor
  • John M. Brown, Andreas Pfaltz, Rutger A. van Santen
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    ABSTRACT: A graphical abstract is available for this content
    08/2014; 4(10). DOI:10.1039/C4CY90040E
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    ABSTRACT: Low-temperature Fischer–Tropsch reaction data are reported for Ru nanoparticles suspended in the water phase. Their activity and selectivity strongly depends on particle size, when varied between 1 to 5 nm. Small particles display high oxygenates selectivity. The Anderson–Schulz–Flory (ASF) chain-growth probability for oxygenates is significantly lower than that observed for hydrocarbons. The chain growth parameter for hydrocarbon formation is independent of particle size. For oxygenates it is constant only for particles larger than 3 nm. Oxygenate and hydrocarbon formation occur on different sites. The ASF chain-growth probability for oxygenate formation increases with temperature. For very small 1.2 nm particles it shows a maximum as a function of temperature. This unusual temperature dependence is due to relatively slow CO dissociation compared to the rate of C–C bond formation.
    07/2014; 4(10). DOI:10.1039/C4CY00709C
  • I. A. W. Filot, R. A. van Santen, E. J. M. Hensen
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    ABSTRACT: A comprehensive density functional theory study of the Fischer–Tropsch mechanism on the corrugated Ru(111) surface has been carried out. Elementary reaction steps relevant to the carbide mechanism and the CO insertion mechanism are considered. Activation barriers and reaction energies were determined for CO dissociation, C hydrogenation, CHx + CHy and CHx + CO coupling, CHxCHy–O bond scission and hydrogenation reactions, which lead to formation of methane and higher hydrocarbons. Water formation that removes O from the surface was studied as well. The overall barrier for chain growth in the carbide mechanism (preferred path CH + CH coupling) is lower than that for chain growth in the CO insertion mechanism (preferred path C + CO coupling). Kinetic analysis predicts that the chain-growth probability for the carbide mechanism is close to unity, whereas within the CO insertion mechanism methane will be the main hydrocarbon product. The main chain propagating surface intermediate is CH via CH + CH and CH + CR coupling (R = alkyl). A more detailed electronic analysis shows that CH + CH coupling is more difficult than coupling reactions of the type CH + CR because of the σ-donating effect of the alkyl substituent. These chain growth reaction steps are more facile on step-edge sites than on terrace sites. The carbide mechanism explains the formation of long hydrocarbon chains for stepped Ru surfaces in the Fischer–Tropsch reaction.
    06/2014; 4(9). DOI:10.1039/C4CY00483C
  • Rutger A. van Santen
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    ABSTRACT: Der perfekte Katalysator: Es wird untersucht, welche Vorzüge der gezielte Entwurf von Katalysatoren aus theoretischen Grundprinzipien bietet. Aspekte der Computerchemie sowie der Kinetik und des physikalischen Zustands des reaktiven Katalysators werden diskutiert.
    Angewandte Chemie 06/2014; DOI:10.1002/ange.201310965
  • Rutger A van Santen
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    ABSTRACT: The perfect catalyst: The advances towards the ability to design a catalyst from first principles are explored. Aspects of computational chemistry as well as the kinetics and physical state of the reactive catalyst are discussed.
    Angewandte Chemie International Edition in English 06/2014; 53(33). DOI:10.1002/anie.201310965 · 13.45 Impact Factor
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    ABSTRACT: Synchrotron X-ray diffraction coupled to atomic pair distribution function analysis and Reverse Monte Carlo simulations is used to determine the atomic-scale structure of Ru nanoparticle catalysts for the Fischer-Tropsch reaction. The rate of CO hydrogenation strongly correlates with the abundance of surface atoms with coordination numbers of 10 and 11. DFT calculations confirm that CO dissociation proceeds with a low barrier on these Ru surface atom ensembles.
    Chemical Communications 04/2014; 50(45). DOI:10.1039/c4cc01687d · 6.72 Impact Factor
  • Xin Zhou, Emiel J. M. Hensen, Rutger A. van Santen, Can Li
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    ABSTRACT: Density functional theory (DFT) calculations are used to explore water adsorption and activation on different α-Ga2O3 surfaces, namely (001), (100), (110), and (012). The geometries and binding energies of molecular and dissociative adsorption are studied as a function of coverage. The simulations reveal that dissociative water adsorption on all the studied low-index surfaces are thermodynamically favorable. Analysis of surface energies suggests that the most preferentially exposed surface is (012). The contribution of surface relaxation to the respective surface energies is significant. Calculations of electron local density of states indicate that the electron-energy band gaps for the four investigated surfaces appears to be less related to the difference in coordinative unsaturation of the surface atoms, but rather to changes in the ionicity of the surface chemical bonds. The electrochemical computation is used to investigate the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) on α-Ga2O3 surfaces. Our results indicate that the (100) and (110) surfaces, which have low stability, are the most favorable ones for HER and OER, respectively.
    Chemistry - A European Journal 04/2014; 20(23). DOI:10.1002/chem.201400006 · 5.70 Impact Factor
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    ABSTRACT: Fischer–Tropsch synthesis is an attractive process to convert alternative carbon sources, such as biomass, natural gas, or coal, to fuels and chemicals. Deactivation of the catalyst is obviously undesirable, and for a commercial plant it is of high importance to keep the catalyst active as long as possible during operating conditions. In this study, the reactivity of CO on carbon-covered cobalt surfaces has been investigated by means of density functional theory (DFT). An attempt is made to provide insight into the role of carbon deposition on the deactivation of two cobalt surfaces: the closed-packed Co(0001) surface and the corrugated Co(112̅1) surface. We also analyzed the adsorption and diffusion of carbon atoms on both surfaces and compared the mobility. Finally, the results for Co(0001) and Co(112̅1) are compared, and the influence of the surface topology is assessed.
    The Journal of Physical Chemistry C 03/2014; 118(10-10):5317-5327. DOI:10.1021/jp4109706 · 4.84 Impact Factor
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    ABSTRACT: The stability of step-edge-type surface sites on cobalt nanoparticles is investigated for particles of increasing size of 1.8, 2.2, and 2.9 nm, that contain 321, 603, and 1157 atoms, respectively. The stability of surface configurations is probed by analyzing the kinetics of the disappearance of step-edge sites as a function of temperature using ReaxFF reactive force field molecular dynamics (MD) simulations. The MD simulations are based on a newly designed reactive force field. Two different activation energy regimes are identified. A low activation barrier of the order of 7 kJ/mol corresponds to single atom movement, which is independent of Co nanoparticle size. Higher activation energies (28, 37, and 22 kJ/mol for the three clusters, respectively) correspond to the shift of overlayer terraces. These concerted shifts appear to be sensitive to particle size, terrace size, and the structure of the facet. Step edges are more stable on larger particles. Shifting of the (111) surface layers leads to transformation of a thin surface layer from the initially face-centered cubic structure to hexagonal close-packed structure.
    The Journal of Physical Chemistry C 03/2014; 118(13). DOI:10.1021/jp500053u · 4.84 Impact Factor
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    ABSTRACT: Liposomes composed of fatty acids and phospholipids are frequently used as model systems for biological cell membranes. In many applications, the encapsulation of proteins and other bio-macromolecules in these liposomes is essential. Intriguingly, the concentration of entrapped material often deviates from that in the solution where the liposomes were formed in. While some reports mention reduced concentrations inside the vesicles, concentrations are also reported to be enhanced in other cases. To elucidate possible drivers for efficient encapsulation, we here investigate the encapsulation of model proteins in spontaneously forming vesicles using molecular dynamics simulations with a coarse grained force field for fatty acids, phospholipids as well as water-soluble and transmembrane proteins. We show that, in this model system, the encapsulation efficiency is dominated by the interaction of the proteins with the membrane, while no significant dependence is observed on the size of the encapsulated proteins nor on the speed of the vesicle formation, whether reduced by incorporation of stiff transmembrane proteins or by the blocking of the bilayer bulging by the presence of another membrane.
    The Journal of Physical Chemistry B 03/2014; 118(12). DOI:10.1021/jp410612k · 3.38 Impact Factor
  • Rutger A van Santen, Minhaj Ghouri, Emiel M J Hensen
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    ABSTRACT: Microkinetics simulations are presented on the intrinsic activity and selectivity of the Fischer-Tropsch reaction with respect to the formation of long chain oxygenated hydrocarbons. Two different chain growth mechanisms are compared: the carbide chain growth mechanism and the CO insertion chain growth mechanism. The microkinetics simulations are based on quantum-chemical data on reaction rate parameters of the elementary reaction steps of the Fischer-Tropsch reaction available in the literature. Because the overall rate constant of chain growth remains too low the CO insertion chain growth mechanism is not found to produce higher hydrocarbons, except for ethylene and acetaldehyde or the corresponding hydrogenated products. According to the carbide mechanism available quantum-chemical data are consistent with high selectivity to long chain oxygenated hydrocarbon production at low temperature. The anomalous initial increase with temperature of the chain growth parameter observed under such conditions is reproduced. It arises from the competition between the apparent rate of C-O bond activation to produce "CHx" monomers to be inserted into the growing hydrocarbon chain and the rate of chain growth termination. The microkinetics simulations data enable analysis of selectivity changes as a function of critical elementary reaction rates such as the rate of activation of the C-O bond of CO, the insertion rate of CO into the growing hydrocarbon chain or the rate constant of methane formation. Simulations show that changes in catalyst site reactivity affect elementary reaction steps differently. This has opposing consequences for oxygenate production selectivity, so an optimizing compromise has to be found. The simulation results are found to be consistent with most experimental data available today. It is concluded that Fischer-Tropsch type catalysis has limited scope to produce long chain oxygenates with high yield, but there is an opportunity to improve the yield of C2 oxygenates.
    Physical Chemistry Chemical Physics 02/2014; 16(21). DOI:10.1039/c3cp54950j · 4.20 Impact Factor
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    ABSTRACT: The reactivity of mononuclear and binuclear iron-containing complexes in ZSM-5 zeolite for catalytic N2O decomposition has been investigated by periodic DFT calculations and microkinetic modeling. On mononuclear sites, the activation of a first N2O molecule is favorable. The rate of catalytic N2O decomposition over Fe2+ and [(FeO)-O-III](+) sites is very low because of the very high barriers (>180 kJ/mol) for the activation of the second N2O molecule necessary to complete the catalytic cycle by O-2 formation. The catalytic cycles for N2O decomposition over binuclear [Fe-II(mu-O)Fe-II](2+) and [Fe-III(mu-O-2)Fe-II](2+) species are interconnected. The catalytic cycle involves the interconversion of these species upon dissociation of N2O on the former complex. As the coordination of reactive Fe centers changes along the reaction coordinate, there are changes in the spin state of the complexes, which affect the overall potential energy diagram. These changes in spin multiplicities facilitate O-2 formation and desorption steps. Based on the DFT-computed potential energy diagrams, microkinetic model simulations were carried out to predict reaction rates and kinetic parameters. The rate of O-2 formation is much higher on binuclear sites than on mononuclear sites. For mononuclear sites, the apparent activation energy is similar to 180 kJ/mol, close to the barrier for dissociating a second N2O molecule. It is consistent with first-order behavior with respect to the partial pressure of N2O. Binuclear sites display much higher reactivity. At low temperature, O-2 desorption is rate controlling, whereas at higher temperatures, the rate is controlled by the two N2O dissociation reactions on [Fe-II(mu-O)Fe-II](2+) and [Fe-III(mu-O)(2)Fe-III](2+). This leads to first-order behavior with respect to N2O. An alternative path involving N2O adsorption and dissociation on [OFe(mu-O)(2)Fe](2+) is energetically favorable but does not contribute to the catalytic cycle because O-2 desorption from the [OFe(mu-O)(2)Fe](2+) intermediate is preferred over the activation of a third N2O molecule due to entropic reasons.
    Journal of Catalysis 12/2013; 308:DOI: 10.1016/j.jcat.2013.08.010. DOI:10.1016/j.jcat.2013.08.010 · 6.07 Impact Factor
  • Rutger A. van Santen, Albert J. Markvoort
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    ABSTRACT: The molecular kinetics of the mechanism of chain growth through CO insertion of the Fischer–Tropsch reaction is analyzed. The maximum chain growth within the CO insertion chain growth model is predicted if the rate of CO activation to give the C1 species that initiates chain growth balances the rate of chain growth termination. The overall rate of chain growth, determined by the elementary rates of CO insertion, hydrogen‐transfer reaction steps, and CO bond cleavage, has to be fast compared to the rate of methanation and the rate of chain growth termination, which gives an oxygenate or hydrocarbon product. However, estimates of rate constants based on quantum‐chemical data predict low chain growth within this CO insertion mechanism, which is mainly caused by the relatively slow rate of CO insertion into the growing chain compared to the rate of product desorption. Such a high barrier for CO insertion is consistent with oxygenate formation through the carbide mechanism pathway. A comparison of the derived expressions for CO consumption shows that the rate of chain growth is limiting within the mechanism of chain growth through CO insertion, whereas within the carbide mechanism it is rate controlled by the rate of CO to CHx monomer formation.
    ChemCatChem 11/2013; 5(11). DOI:10.1002/cctc.201300173 · 5.04 Impact Factor
  • Rutger van Santen
    ChemInform 10/2013; 44(42). DOI:10.1002/chin.201342279

Publication Stats

14k Citations
2,489.56 Total Impact Points

Institutions

  • 2014
    • University of Oxford
      Oxford, England, United Kingdom
  • 1988–2014
    • Technische Universiteit Eindhoven
      • • Department of Chemical Engineering and Chemistry
      • • Institute for Complex Molecular Systems
      • • Schuit Institute of Catalysis
      • • Department of Applied Physics
      Eindhoven, North Brabant, Netherlands
  • 2011
    • Middle East Technical University
      • Department of Chemical Engineering
      Engüri, Ankara, Turkey
  • 2010
    • University of Liverpool
      Liverpool, England, United Kingdom
    • University of Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 1999–2010
    • Delft University of Technology
      • • Department of Process and Energy (P&E)
      • • Applied Geophysics and Petrophysics
      Delft, South Holland, Netherlands
  • 2008
    • University of Leuven
      • Centre for Surface Chemistry and Catalysis (COK)
      Louvain, Flanders, Belgium
  • 2003–2005
    • University of Groningen
      • Centre for Ecological and Evolutionary Studies (CEES)
      Groningen, Province of Groningen, Netherlands
  • 2002–2005
    • Boreskov Institute of Catalysis
      Novo-Nikolaevsk, Novosibirsk, Russia
    • Federal University of Rio de Janeiro
      Rio de Janeiro, Rio de Janeiro, Brazil
  • 2004
    • IMSA Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 2001–2003
    • National Technical University of Ukraine Kiev Polytechnic Institute
      • Faculty of Chemical Technology
      Kievo, Kyiv City, Ukraine
  • 2000
    • Northwestern University
      • Center for Catalysis and Surface Science
      Evanston, Illinois, United States
  • 1998
    • The University of Edinburgh
      • School of Chemistry
      Edinburgh, Scotland, United Kingdom