Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session D1: Focus Session: Surface Chemistry and Catalysis II |
Hide Abstracts |
Sponsoring Units: DCP Chair: Charlie Sykes, Tufts University Room: 103/105 |
Monday, March 3, 2014 2:30PM - 2:42PM |
D1.00001: Plyler Prize and APS Fellow Introductions Gilbert Nathanson The Division of Chemical Physics is delighted to announce the 2013 APS Fellows sponsored by DCP and to honor the 2014 Earl K. Plyler Prize Award winner. The new APS Fellows are: Ilan Benjamin, Hua Guo, Manos Mavrikakis, Josef Paldus, Joern Siepmann, Hans-Peter Steinrueck, Douglas Tobias, Angela Wilson, and Yijing Yan. The citations for each awardee will be read out loud. I will also introduce Prof. Lai-Sheng Wang of the Department of Chemistry at Brown University, who was awarded the 2014 Plyler Prize for Molecular Spectroscopy and Dynamics. Please come learn about these extraordinary scientists during this prize session. Prof. Wang's Plyler Prize talk will follow immediately after this introduction. For more information, see http://www.aps.org/units/dcp/. [Preview Abstract] |
Monday, March 3, 2014 2:42PM - 3:18PM |
D1.00002: Earle K. Plyler Prize: Probing the Structural Evolution and Size-Dependent Reactivity of Gold Clusters by Photoelectron Spectroscopy Invited Speaker: Lai-Sheng Wang Gold has attracted much interest in nanoscience because of its emerging catalytical and optical properties at the nanometer scale. A prerequisite to elucidate the molecular mechanisms of the catalytic effects of nanogold is a detailed understanding of the structural and electronic properties of gold clusters as a function of size. Negatively charged gold clusters (Au$_{n}^{-})$ up to $n =$ 12 were known to be planar. Using photoelectron spectroscopy and computational chemistry, we found that Au$_{16}^{-}$ to Au$_{18}^{-}$ possess hollow cage structures, while Au$_{20}^{-}$ was found to have a high symmetry tetrahedral structure. Beyond Au$_{20}^{-}$, we have found that low symmetry core-shell type structures started to emerge at Au$_{25}^{-}$. The size-dependent reactivity of O$_{2}$ with gold clusters was further studied using photoelectron spectroscopy. Previous works showed that only even-sized Au$_{n}^{-}$ clusters react with O$_{2}$, whereas odd-sized Au$_{n}^{-}$ clusters are nonreactive. Superoxo-type Au$_{n}$(O$_{2}^{-})$ complexes were proposed for even-sized clusters. We observed van der Waals complexes of odd-sized Au$_{n}^{-}$ clusters with O$_{2}$, confirming the inertness of the odd-sized Au$_{n}^{-}$ toward O$_{2}$. This observation led to new insight into how neutral even-sized Au$_{n}$ clusters interact with O$_{2}$. Further studies revealed that there is a superoxo to peroxo chemisorption transition for the O$_{2}$ interaction with even-sized Au$_{n}^{-}$ clusters. The O$_{2}$ in the peroxo O$_{2}$Au$_{n}^{-}$ complexes is much more activated (with a longer O--O bond length), suggesting that this mode of chemisorption may play a more important role in the O$_{2}$ activation by gold nanoparticles. [Preview Abstract] |
Monday, March 3, 2014 3:18PM - 3:30PM |
D1.00003: Understanding the Composition and Reactivity of Au/Cu Electrocatalyst Nanoparticles in Solution Using Highly Accurate Reactive Potentials Nongnuch Artrith, Alexie Kolpak The shape, size, and composition of catalyst nanoparticles can have a significant influence on their catalytic activity. Understanding such structure-reactivity relationships is crucial for the optimization of industrial catalysts and the design of novel catalysts with enhanced properties. In this work, we investigate the equilibrium shape and surface structure/composition of Au/Cu nanoparticles in solution, which have recently been shown to be stable and efficient catalysts for CO$_{2}$ reduction [1]. Using a combination of density functional theory calculations and large-scale Monte-Carlo and molecular dynamics simulations with reactive atomistic potentials, we determine how the nanoparticle shape, surface structure, and surface stoichiometry (i.e., fraction of Au at the surface relative to overall composition), evolve as a function of varying catalytic conditions. We discuss the effects of these changes on the surface electronic structure and binding energies of CO$_{2}$, H$_{2}$, and CH$_{3}$OH. Our results emphasize the important relationships between catalytic environment (e.g., solvent effects), catalyst structure, and catalytic activity. [1] Z. Xu, E. Lai, Y. Shao-Horn, and K. Hamand-Schifferli, Chem. Commun. 48, 5626-2528 (2012). [Preview Abstract] |
Monday, March 3, 2014 3:30PM - 3:42PM |
D1.00004: Density Functional Theory Investigation of Adsorption Properties of CO, CO$_2$ and H$_2$O on $\gamma$-Al$_2$O$_3$ Supported Pt Clusters Mehmet Gokhan Sensoy, Hande Ustunel, Daniele Toffoli The water-gas shift reaction is a key catalytic process for the production of clean H$_2$ gas for fuel cells.\footnote{M. S. Dresselhaus and I. L. Thomas, Nature 414, 332 (2001)} In this study, we use plane wave pseudopotential density functional theory to study the adsorption properties and the activation of CO, CO$_2$ and H$_2$O on Pt clusters supported on the (001) surface of $\gamma$-Al$_2$O$_3$. A systematic study has been conducted to identify the most stable adsorption sites for both monoatomic and diatomic Pt clusters. Several stable adsorption geometries have been identified for the adsorbates, and their interaction with both the precious metal and the support is characterized in terms of adsorption energies and the nature of the bond between the adsorbed molecules and the precious metal. [Preview Abstract] |
Monday, March 3, 2014 3:42PM - 4:18PM |
D1.00005: Correlating structure and function for nanoparticle catalysts Invited Speaker: Graeme Henkelman Better oxygen reduction catalysts are needed to improve the efficiency and lower the cost of fuel cells. Metal nanoparticles are good candidates for new catalysts because their catalytic properties are different from bulk metals, and are sensitive to particle size, shape and composition. The electronic structure can be determined for small particles, making it possible to optimize particles for a desired reaction. Here, we calculate the electronic structure of 1 nm core/shell particles and show how the energy of electrons in the shell can tune the binding of oxygen by varying the core metal. Transition state calculations for O2 dissociation on the nanoparticle surface show that the d-band center is a good measure of the activation and reaction energies. Two factors are found to be significant for determining the catalytic activity of small nanoparticles; charge transfer in core/shell particles and the rigidity of alloy particles. [Preview Abstract] |
Monday, March 3, 2014 4:18PM - 4:30PM |
D1.00006: Catalytic Properties of Graphene-Supported Pt13 Nanoclusters Ioanna Fampiou, Ashwin Ramasubramaniam Graphene is of considerable interest as a support material for fuel cell electrodes due to its high surface area, high mechanical strength and exceptional electrical conductivity. Here, using density functional theory calculations we investigate the electronic and catalytic properties of Pt$_{13}$ clusters supported on pristine and defective graphene. We show that defects in the graphene support significantly stabilize Pt clusters against sintering. Strong cluster-substrate interactions are also found to substantially shift the $d$ band centers of the Pt clusters. Specifically, we investigate the adsorption of CO and O on Pt clusters bound at defects in graphene and show that such defect-supported clusters adsorb CO and O more weakly than clusters supported on pristine graphene or entirely unsupported clusters. We examine the kinetics of the CO oxidation reaction and demonstrate that graphene-supported Pt$_{13}$ nanoclusters--despite the low coordination of surface atoms--possess comparable catalytic activity with macroscopic Pt(111) surfaces and, in general, superior catalytic activity compared to unsupported clusters. Our results suggest possible avenues for controlling the dispersion and catalytic activity of Pt nanoclusters on graphene supports via defect engineering. [Preview Abstract] |
Monday, March 3, 2014 4:30PM - 4:42PM |
D1.00007: Unexpected carboxylate like CO adsorption at the Sr$_3$Ru$_2$O$_7$ (001) surface Marcel Hieckel, Florian Mittendorfer, Josef Redinger, Bernhard Stoeger, Zhiming Wang, Michael Schmid, Ulrike Diebold Oxide perovskite materials have attracted enormous attention because of a variety of intriguing physical properties ranging from catalysis to multiferroicity. We present a combined experimental and ab-initio (DFT) study with the Vienna Ab initio Simulation Package (VASP) on the adsorption of CO at the Sr$_3$Ru$_2$O$_7$ (001) surface. We identify both a physisorbed and a chemisorbed CO configuraton. Unexpectedly, in the latter case adsorption occurs in a carboxylate (COO) like state. Both configurations have been confirmed by detailed STM experiments and simulations. In addition we find only a small barrier for the carboxylate formation on the surface. Work supported by the Austrian FWF, SFB F45 (FOXSI). [Preview Abstract] |
Monday, March 3, 2014 4:42PM - 4:54PM |
D1.00008: Theoretical Study of Chemisorption on Nickel and Palladium Clusters Ajit Hira, Jose Pacheco, Danelle Jaramillo, Frank Naranjo We continue our interest in the chemisorption of different atomic and molecular species on small clusters of metallic elements, by examining the interactions of H, O and F atoms with Pd$_{\mathrm{n}}$ and Ni$_{\mathrm{n}}$ clusters (n $=$ 2 thru 20). Transition-metal clusters are specially suited for the study of quantum size effects and for formation of metallic states, and are ideal candidates for catalytic processes. Hybrid ab initio methods of quantum chemistry (particularly the DFT-B3LYP model) are used to derive optimal geometries for the clusters of interest. We compare calculated binding energies, bond-lengths, ionization potentials, electron affinities and HOMO-LUMO gaps for the clusters of the two different metals. Of particular interest are the comparisons of binding strengths at the three important types of sites: edge (E), hollow (H), on-top (T), threefold sites and fourfold sites. Effects of crystal symmetries corresponding to the bulk structures for the two metals are investigated. The implications for the molecular dissociation of the H$_{2}$ and O$_{2}$ species will be considered. [Preview Abstract] |
Monday, March 3, 2014 4:54PM - 5:06PM |
D1.00009: Quantum Monte Carlo Calculations of Pt Nanoclusters and (111) Surface William Parker, Anouar Benali, Luke Shulenburger, Jeongnim Kim, Nichols Romero, Jeffrey Greeley Although density functional theory (DFT) has been successfully used to analyze problems in surface catalysis and electrochemistry at a molecular level, there are several important classes of problems where DFT fails spectacularly, predicting incorrect adsorption energies and binding sites. Better understanding these failures and benchmarking methods for correcting them motivates a quantum Monte Carlo (QMC) investigation of platinum nanoclusters and the platinum (111) surface. To evaluate the transferability of our platinum pseudopotential, we first present the fixed-node diffusion Monte Carlo (DMC) equation of state and cohesive energy for fcc platinum. We then show the binding energies of icosahedral nanoclusters with increasing size and the (111) surface energy to lay the groundwork for investigation of adsorption on these catalytically important phases of platinum. [Preview Abstract] |
Monday, March 3, 2014 5:06PM - 5:18PM |
D1.00010: Morphology and the Catalytic Activity of Pd Nanoparticles on TiO$_{2}$- and SrO- Terminated SrTiO$_{3}$ Nanocuboids Bor-Rong Chen, Cassandra George, Linhua Hu, Peter C. Stair, Kenneth R. Poeppelmeier, Richard P. Van Duyne, Yuyuan Lin, Michael J. Bedzyk We report how different surface terminations of SrTiO$_{3}$ (STO) influence the facetted-shape and catalytic performance of supported Pd nanoparticles. A new approach to catalyst studies by synthesizing STO nanocuboids with either TiO$_{2}$- or SrO- terminated surface as a support will be presented. The nanocuboids have well defined (001) surfaces and high surface area; therefore, practical catalytic reaction studies can be carried out while the support resembles the model catalyst surface. This study investigates the morphology and the catalytic activity of Pd nanoparticles deposited by atomic layer deposition (ALD) on STO nanocuboids with TiO$_{2}$ and SrO terminations. We demonstrate that the wt\% loading and Pd nanoparticle size can be controlled by the number of ALD cycles. The morphology and chemical nature of the Pd particles are studied by TEM, X-ray scattering, and X-ray absorption fine structure measurements. [Preview Abstract] |
Monday, March 3, 2014 5:18PM - 5:30PM |
D1.00011: ABSTRACT WITHDRAWN |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700