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February 2019
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  1. Condensed-Matter Physics & Materials Science Seminar

    4:30 pm, Bldg. 480 Conference Room

    Hosted by: Jing Tao

    The ever increasing consumption of fossil fuels for transportation causes climate change causing a growing concern about their future availability and further adverse environmental effects. To address this issue, the concept of CO2 neutral fuels-based energy cycle was brought out. The key reactions in that concept are electrochemical methanol oxidation (MOR), ethanol oxidation reaction (EOR), and CO2 reduction reaction (CO2RR). These all are elctrocatalysis research challenges being slow even at the best catalyst that hamper application of fuel cells, and bring environmental benefits. My research made these improvements of catalysts for the key reactions. In-situ electrochemical infrared reflective absorbance spectrum (EC-IRRAS) reveals that at lower temperature, such reaction is not complete and generates more formate; at elevated temperature, such reaction is complete to carbonate. Ethanol is one of the ideal fuels for fuel cells, but requires highly improved catalysts. Au@PtIr/C catalyst was synthesized with a surfactant-free wet-chemistry approach. Transmission electron microscope (TEM) characterization confirms the monolayer/sub-monolayer Pt-Ir shell, gold core structure. The catalyst has a very high mass activity of 58 A/mg at peak current. In situ EC-IRRAS reveals that C-C bond is cleaved upon contact with the catalyst surface leading to ethanol complete oxidation to CO2. Related researches on methodologies, included in situ TEM to help obtaining catalysts improvements, give morphologic, structural and spectroscopic information at wide range from hundreds of microns to sub-nanometer coupled with various detectors. Microelectromechanical System (MEMS) based chips technology enables TEM observation in operando, with liquid-flow-cell chips and electrochemistry chips designed and fabricated. Ag@Au hollow cubes synthesis via galvanic replacement of Au on Ag cubes was investigated with in situ TEM. The results demonstrate abnormal react

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  1. Chemistry Department Seminar

    11 am, Room 300, 3rd floor, Chemistry Bldg. 555

    Hosted by: Sanjaya Senanayake

    Metal-ceria catalysts are promising systems for industrially important reactions such as the water-gas shift reaction for hydrogen production, methane dry reforming (DRM: CH4+CO2 ? 2H2+2CO), and the direct conversion of methane to methanol (DMTM: CH4+ ½ O2 ? CH3OH). However, the complexity of real (powder) catalysts hinders the fundamental understanding of how they work, which is essential for their rational design. Specifically, the role of ceria in the catalytic activity of ceria-based systems is still not fully understood. To unravel it, well-defined ceria-based model cata-lysts consisting of metal nanoparticles deposited on a ceria surface are prepared experimentally or created theoretically and investigated. In this talk, recent results on ceria-supported Ni, Co and Cu model catalysts will be discussed, as examples of catalysts for DRM.1-3 The emphasis is here put on theoretical studies in combination with experiments using ambient pressure X-ray photoelectron spectroscopy, and special attention is given to the effects of ceria as catalyst support. The ability of ceria to stabilize oxidized species (MOx: Co2+ and Ni2+) on the CeO2 surface, by relocalizing electrons on localized f-states, and metal-lic ones (Co0, Ni0) on the reduced CeO2-x support, is essential for CH4 activation ?that occur at tem-peratures as low as 300 K? and its reforming at relatively low temperatures (~700 K). Also, the Ni/ceria system is considered for H2O activation and methanol synthesis from methane and wa-ter.4,5

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  1. Chemistry Department Colloquium

    11 am, Hamilton Seminar Room, Bldg. 555

    Hosted by: Ping Liu

    Atomic simulation is able to solve more chemical problems than ever before due to advances in high performance computing and data science tools. Two case studies are presented to illustrate this point. One case study is the water-gas shift reaction catalyzed by platinum clusters deposited on metal oxide (Pt/MO2). The water-gas shift reaction is the most widely applied reaction in industry for the production of hydrogen which is an environmentally-friendly fuel. Furthermore, water-gas shift may be conducted on domestically produced shale gas, alleviating foreign dependence on oil. Three hypotheses regarding the active site for the water–gas shift reaction are the interface edge of Pt/MO2 catalysts, the interface corner, and the platinum terrace (pure platinum). The hypotheses are tested against experimental kinetic data. Uncertainties associated with density functional theory (DFT) calculations and model errors of microkinetic models of the active sites are informed and verified using Bayesian inference and predictive validation on the experiments. Our results suggest the metal oxide support is essential for the activity of the catalyst for water-gas shift, which aids the rational design of catalysts for the water-gas shift reaction. In the second case study, large data sets of organic reactions are investigated using machine learning tools. Reactions which are not labeled with a solvent are automatically labeled, which impacts automated chemical process design and may be utilized as an every-day tool by chemists. The machine learning solvent selections are tested against an expert chemist. In a broad sense, the methods developed within this work improve the reliability of atomic simulations and the incorporation of machine learning to catalysis research.

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  1. MAR

    4

    Monday

    Chemistry Department Colloquium

    "Anineutrino Reactor Monitoring"

    Presented by Professor Patrick Huber, Virginia Tech

    11 am, Hamilton Seminar Room, Bldg. 555

    Monday, March 4, 2019, 11:00 am

    Hosted by: Minfang Yeh

    Nuclear reactors are the brightest man-made neutrino sources and have been the workhorse of neutrino physics since the discovery of the neutrino. In the 1970s Lev Mikaelyan realized that neutrinos also can be used to learn about the internal state of a nuclear reactor. The past decade has seen a significant increase in the interest in reactor neutrinos, thanks to the theta-13 experiments and the search for sterile neutrinos. In particular, I will discuss case studies we have performed for the historical case of the 1990s nuclear crisis in the Democratic People's Republic of Korea and for the IR-40 reactor in Iran. I will report on on-going efforts to develop suitable detectors for surface deployment close to a nuclear reactor and comment on the role coherent elastic neutrino nucleus scattering may play. With the most recent results from PROSPECT, CHANDLER and others, for the first time, a real world capability exists and I will present recent efforts by an international group of reactor neutrino experts with regards to North Korea, which were published in Science [Science, 362, (2018) 649-650)].

  1. Chemistry Department Colloquium

    "Atomic Simulation and Data Science Applied to Catalysis"

    Presented by Eric A. Walker, State University of NY at Buffalo

    Tuesday, February 19, 2019, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Ping Liu

    Atomic simulation is able to solve more chemical problems than ever before due to advances in high performance computing and data science tools. Two case studies are presented to illustrate this point. One case study is the water-gas shift reaction catalyzed by platinum clusters deposited on metal oxide (Pt/MO2). The water-gas shift reaction is the most widely applied reaction in industry for the production of hydrogen which is an environmentally-friendly fuel. Furthermore, water-gas shift may be conducted on domestically produced shale gas, alleviating foreign dependence on oil. Three hypotheses regarding the active site for the water–gas shift reaction are the interface edge of Pt/MO2 catalysts, the interface corner, and the platinum terrace (pure platinum). The hypotheses are tested against experimental kinetic data. Uncertainties associated with density functional theory (DFT) calculations and model errors of microkinetic models of the active sites are informed and verified using Bayesian inference and predictive validation on the experiments. Our results suggest the metal oxide support is essential for the activity of the catalyst for water-gas shift, which aids the rational design of catalysts for the water-gas shift reaction. In the second case study, large data sets of organic reactions are investigated using machine learning tools. Reactions which are not labeled with a solvent are automatically labeled, which impacts automated chemical process design and may be utilized as an every-day tool by chemists. The machine learning solvent selections are tested against an expert chemist. In a broad sense, the methods developed within this work improve the reliability of atomic simulations and the incorporation of machine learning to catalysis research.

  2. Chemistry Department Seminar

    "Theoretical and in situ studies for the reactivity of metal-ceria (111) surfac-es: Importance of strong metal-support interactions"

    Presented by M. Verónica Ganduglia-Pirovano, Instituto de Catálisis y Petroleoquímica Consejo Superior de Investigaciones Científicas,, Spain

    Friday, February 15, 2019, 11 am
    Room 300, 3rd floor, Chemistry Bldg. 555

    Hosted by: Sanjaya Senanayake

    Metal-ceria catalysts are promising systems for industrially important reactions such as the water-gas shift reaction for hydrogen production, methane dry reforming (DRM: CH4+CO2 ? 2H2+2CO), and the direct conversion of methane to methanol (DMTM: CH4+ ½ O2 ? CH3OH). However, the complexity of real (powder) catalysts hinders the fundamental understanding of how they work, which is essential for their rational design. Specifically, the role of ceria in the catalytic activity of ceria-based systems is still not fully understood. To unravel it, well-defined ceria-based model cata-lysts consisting of metal nanoparticles deposited on a ceria surface are prepared experimentally or created theoretically and investigated. In this talk, recent results on ceria-supported Ni, Co and Cu model catalysts will be discussed, as examples of catalysts for DRM.1-3 The emphasis is here put on theoretical studies in combination with experiments using ambient pressure X-ray photoelectron spectroscopy, and special attention is given to the effects of ceria as catalyst support. The ability of ceria to stabilize oxidized species (MOx: Co2+ and Ni2+) on the CeO2 surface, by relocalizing electrons on localized f-states, and metal-lic ones (Co0, Ni0) on the reduced CeO2-x support, is essential for CH4 activation ?that occur at tem-peratures as low as 300 K? and its reforming at relatively low temperatures (~700 K). Also, the Ni/ceria system is considered for H2O activation and methanol synthesis from methane and wa-ter.4,5

  3. Condensed-Matter Physics & Materials Science Seminar

    "Novel Electrochemistry for Fuel Cell Reactions: Efficient Synthesis and New Characterization Methods"

    Presented by Zhixiu Liang

    Wednesday, February 6, 2019, 4:30 pm
    Bldg. 480 Conference Room

    Hosted by: Jing Tao

    The ever increasing consumption of fossil fuels for transportation causes climate change causing a growing concern about their future availability and further adverse environmental effects. To address this issue, the concept of CO2 neutral fuels-based energy cycle was brought out. The key reactions in that concept are electrochemical methanol oxidation (MOR), ethanol oxidation reaction (EOR), and CO2 reduction reaction (CO2RR). These all are elctrocatalysis research challenges being slow even at the best catalyst that hamper application of fuel cells, and bring environmental benefits. My research made these improvements of catalysts for the key reactions. In-situ electrochemical infrared reflective absorbance spectrum (EC-IRRAS) reveals that at lower temperature, such reaction is not complete and generates more formate; at elevated temperature, such reaction is complete to carbonate. Ethanol is one of the ideal fuels for fuel cells, but requires highly improved catalysts. Au@PtIr/C catalyst was synthesized with a surfactant-free wet-chemistry approach. Transmission electron microscope (TEM) characterization confirms the monolayer/sub-monolayer Pt-Ir shell, gold core structure. The catalyst has a very high mass activity of 58 A/mg at peak current. In situ EC-IRRAS reveals that C-C bond is cleaved upon contact with the catalyst surface leading to ethanol complete oxidation to CO2. Related researches on methodologies, included in situ TEM to help obtaining catalysts improvements, give morphologic, structural and spectroscopic information at wide range from hundreds of microns to sub-nanometer coupled with various detectors. Microelectromechanical System (MEMS) based chips technology enables TEM observation in operando, with liquid-flow-cell chips and electrochemistry chips designed and fabricated. Ag@Au hollow cubes synthesis via galvanic replacement of Au on Ag cubes was investigated with in situ TEM. The results demonstrate abnormal react

  4. Symposium on the 60th Anniversary of the Life-Saving Technetium-99m

    Wednesday, November 7, 2018, 3 pm
    Hamilton Seminar Room, Bldg. 555

    Speakers will present talks on technetium and nuclear medicine, including the history of the development of the Tc-99m generator at Brookhaven. The talks will be followed by a reception in the Chemistry Lobby.

  5. Chemistry Department Seminar

    "Synchrotron-based X-ray Absorption Spectroscopy for In Situ and Operando Studies of Nanoporous Catalysts"

    Presented by Kirill A. Lomachenko, European Synchrotron Radiation Facility (ESRF), Grenoble, France, France

    Monday, November 5, 2018, 11 am
    Room 300, Chemistry Bldg. 555

    Hosted by: Anatoly Frenkel

    X-ray absorption spectroscopy (XAS) has proven to be a very powerful tool for rationalization of catalytic processes because of the possibility to determine oxidation state and coordination geometry of catalytically active species in operando regime. The seminar will be focused on the advanced facilities for chemical XAS studies available at BM23 and ID24 beamlines of the ESRF synchrotron, which allow to exploit simultaneously a wide range of complementary techniques, make use of flexible sample environment, and obtain high-quality data in the timescale from minutes down to milliseconds. As a case study, recent work on the investigation of the local environment and electronic structure of the active centers of Cu-zeolites in deNOx and methane-to-methanol processes will be discussed.

  6. NSLS-II Friday Lunchtime Seminar

    "Materials Tribology: An Application-Driven Field with Rich Opportunities for Fundamental Studies of Surface Chemistry, Physics, Structure"

    Presented by Brandon A. Krick, Department of Mechanical Engineering and Mechanics, Lehigh University

    Friday, November 2, 2018, 12 pm
    NSLS-II Bldg. 743 Rm 156

    Hosted by: Ignace Jarrige

    The significant economic (~3-6% of developed countries GDP) and environmental (several percent of our annual energy consumption) impacts of friction and wear make tribology is an important, application-driven field. However, there is an opportunity and need for inherently fundamental studies on surface chemistry, physics and structure to elucidate fundamental mechanisms for friction and wear. The non-equilibrium and transient nature of shear-induced changes caused by contacting surfaces in relative motion requires both in situ and ex situ advanced characterization techniques; many of these only available at the light source at Brookhaven. A brief overview of shear-induced (sliding friction/wear) alterations of surfaces will be presented for material systems including: - environmental and tribochemistry molybdenum disulphide based coatings for space applications - shear-induced band bending in GaN - mechanochemistry of polymer nanocomposites

  7. Chemistry Department Seminar

    ""Size control of supported metals for catalysis""

    Presented by Xiao Yan Liu, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China), China

    Tuesday, October 30, 2018, 11 am
    Room 300 - 3rd Flr. Chemistry Bldg. 555

    Hosted by: Sanjaya Senanayake

    Catalysis by supported metals is size sensitive, so the size control is extremely important. Here, I will present two examples for the size control of catalysis. One is the size control of gold catalysts by tuning the metal support interaction. In the last decade, we've developed several methods to control the particle size of gold, for example, adding a second metal to form alloy with gold, using the thiolated gold nanoclusters as the precursor of gold catalysts, and so on. The other example focuses on single-atom catalysis that has emerged as a new frontier in heterogeneous catalysis and shown distinctive performances in a series of oxidation and hydrogenation reactions. The ways we developed to stabilize the single atoms will be introduced. The mechanism for the stabilization of the nanoparticles/single atoms were proposed based on the characterization by aberration-corrected HAADF-STEM, in situ EXAFS and DFT calculations.

  8. PubSci at the Parrish

    "Illumination: Revealing the Secret Chemistry of Oil Paintings"

    Friday, September 21, 2018, 7 pm
    Parrish Art Museum 279 Montauk Hwy., Water Mill, N

  9. Chemistry Department Colloquium

    "Proton-Coupled Electron Transfer in Catalysis and Energy Conversion"

    Presented by Dr. Sharon Hammes-Schiffer, Department of Chemistry, Yale University

    Monday, September 10, 2018, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Mehmed Zahid Ertem

    Proton-coupled electron transfer (PCET) reactions play a vital role in a wide range of chemical and biological processes. This talk will focus on recent advances in the theory of PCET and applications to catalysis and energy conversion. The quantum mechanical effects of the active electrons and transferring proton, as well as the motions of the proton donor-acceptor mode and solvent or protein environment, are included in a general theoretical formulation. This formulation enables the calculation of rate constants and kinetic isotope effects for comparison to experiment. Recent extensions enable the study of heterogeneous as well as homogeneous interfacial PCET processes. Applications to PCET in molecular electrocatalysts for hydrogen production and water splitting, photoreduced zinc-oxide nanocrystals, and the Volmer reaction will be discussed. These studies have identified the thermodynamically and kinetically favorable mechanisms, as well as the role of proton relays, and are guiding the theoretical design of more effective catalysts. In addition, recent developments of theoretical approaches for simulating the ultrafast dynamics of photoinduced PCET, along with applications to solvated molecular systems and photoreceptor proteins, will be discussed.

  10. Chemistry Department Seminar

    "Synthesis of Fuels and Chemicals by Electroreduction over Copper Catalysts"

    Presented by Elizabeth J. Biddinger, The City College of New York, CUNY

    Monday, August 6, 2018, 11 am
    Room 300 - 3rd Flr. Chemistry Bldg. 555

    Hosted by: Sanjaya Senanayake

    Electrochemical synthesis methods offer opportunities to perform reactions under benign reaction conditions (at or near room temperature and pressure), use less harmful or waste-generating reaction steps, and perform selective reactions. In electroreduction reactions, externally-supplied hydrogen that is generally needed for reduction is not required. Rather, electrons, frequently paired with the electrolyte, are the reducing agents. New opportunities for utilization of electrochemical reactions exist with the emerging renewable electricity generation market. Due to the intermittent supply sources for many renewable electricity systems, excess electricity gets generated when peak generation (sunny or windy periods) does not match with demand. Electrochemical reactions can be performed at relatively low costs with this excess electricity to synthesize fuels for later use or chemicals. The work presented here will illustrate two synthesis systems via electroreduction – carbon dioxide electroreduction to hydrocarbons and furfural (a biomass-derived species) electrochemical hydrogenation and hydrogenolysis (ECH) to fuels and chemicals. Both of these reactions are performed over copper electrodes, serving as the catalysts for the system. Copper is utilized because of its unique balance between being active for the electroreduction and less active for the undesired side reaction hydrogen evolution. In CO2 electroreduction, copper is the only known metal to produce significant quantities of hydrocarbons. By tuning the morphology, the selectivity between ethylene and methane can be tuned. The results of morphological differences and the dynamic nature of copper surfaces will be discussed in terms of electrodeposition and the resulting CO2 electroreduction performance. In furfural ECH, both 2-methyl furan and furfuryl alcohol can be formed, while over many other metals 2-methyl furan is not formed. The reaction conditions for furfural ECH si

  11. Chemistry Department Seminar

    "Triggered Reversible Phase Transformation between Layered and Spinel Structure via Intercalated Hetero Species in Sodium Birnessite"

    Presented by Yong-Mook Kang, Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul, 04620, Republic of Korea., Korea, Republic of (South)

    Monday, July 23, 2018, 11 am
    Room 300, 3rd Flr. Chemistry Bldg. 555

    Hosted by: Xiao-Qing Yang

    Phase transformation of layered structure into spinel structure has been detrimental for most of layered oxide cathodes. Even if a lot of efforts have been made to relieve this highly irreversible phase transformation, there have been few successful results. However, we firstly observed the possibility to make this irreversible phase transformation extremely reversible by utilizing Na- birnessite (NaxMnO2•yH2O; Na-bir) as a basic structural unit, which has distinctive layered structure containing crystal water. Herein, the crystal water in the structure contributes to generating metastable spinel-like phase, which is the key factor for making this unusual reversibility happen. The reversible structural rearrangement between layered and spinel-like phases during electrochemical reaction could activate new cation sites and enhance ion diffusion with higher structural stability. This unprecedented reversible phase transformation between spinel and layered structure was deeply analyzed via combined ex situ soft and hard X-ray absorption spectroscopy (XAS) analysis with in situ X-ray diffraction (XRD). Fundamental mechanism on this reversible phase transformation was theoretically elucidated and confirmed by kinetic investigation using first-principle calculation. These results provide deep insight into novel class of intercalating materials which can deal with highly reversible framework changes, and thus it can pave an innovative way for the development of cathode materials for next- generation rechargeable batteries.

  12. Chemistry Department Colloquium

    "Turning Base Metals into Precious Metals: Nanostructured Early Transition Metal Carbides and Nitrides"

    Presented by Levi Thompson, University of Michigan, Department of Chemical Engineering,

    Monday, July 9, 2018, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Sanjaya Senanayake

    The addition of carbon and nitrogen to early transition metals like molybdenum and vanadium can result in materials with properties that are similar to those of platinum group metals (PGMs). In the mid-1970s, for example, it was discovered that tungsten carbides can catalyze hydrogenation reactions that previously were only known for PGMs, and more recently we observed that molybdenum nitrides are capable of bulk hydrogen storage like Pd. Since then, early transition metal carbides and nitrides have been investigated for a variety of reactions. This paper will describe our work to design and synthesize nanostructured early transition metal carbides and nitrides for reactions including selective hydrogenations. Our research has focused on understanding the genesis of the materials, unraveling the reaction mechanisms and determining structure-function relationships that will enable the rational design of these materials. Of particular interest are CO2 hydrogenation and ammonia synthesis, reactions for which new catalysts are needed to reduce energy consumption.

  13. Chemistry Department Seminar

    "Nanowires Devices for Emerging Energy Storage"

    Presented by Liqiang Mai, Wuhan University of Technology, China

    Friday, June 15, 2018, 11 am
    Room 300 - Third Floor - Chemistry Bldg. 555

    Hosted by: Xiao-Qing Yang

    One-dimensional nanomaterials can offer large surface area, facile strain relaxation upon cycling and efficient electron transport pathway to achieve high electrochemical performance. Hence, nanowires have attracted increasing interest in energy related fields. We designed the single nanowire electrochemical device for in situ probing the direct relationship between electrical transport, structure, and electrochemical properties of the single nanowire electrode to understand intrinsic reason of capacity fading. The results show that during the electrochemical reaction, conductivity of the nanowire electrode decreased, which limits the cycle life of the devices. We have developed a facile and high-yield strategy for the oriented formation of CNTs from metal−organic frameworks (MOFs). The appropriate graphitic N doping and the confined metal nanoparticles in CNTs both increase the densities of states near the Fermi level and reduce the work function, hence efficiently enhancing its oxygen reduction activity. Then, we fabricated a field-tuned hydrogen evolution reaction (HER) device with an individual MoS2 nanosheet to explore the impact of field effect on catalysis. In addition, we demonstrated the critical role of structural H2O on Zn2+ intercalation into bilayer V2O5·nH2O. The results suggest that the H2O-solvated Zn2+ possesses largely reduced effective charge and thus reduced electrostatic interactions with the V2O5 framework, effectively promoting its diffusion. We also identified the exciting electrochemical properties (including high electric conductivity, small volume change and self-preserving effect) and superior sodium storage performance of alkaline earth metal vanadates through preparing CaV4O9 nanowires. Our work presented here can inspire new thought in constructing novel one-dimensional structures and accelerate the development of energy storage applications.

  14. Chemistry Department Seminar

    "Astrochemistry in the Laboratory – Combining Theory and Experiment"

    Presented by Kelvin Lee, Harvard-Smithsonian Center for Astrophysics

    Monday, June 11, 2018, 11 am
    Room 300, 3rd Floor, Chemistry Bldg. 555

    Hosted by: Greg Hall

    Brief overview of the laboratory and theoretical efforts in astrochemistry at the Harvard Smithsonian Center for Astrophysics. Will highlight one of our areas of research – the characterization and spectroscopy of molecular isomers in space by showcasing two recent projects (1) the rotational spectroscopy of ethynethiol (HCCSH), a higher energy isomer of thioketene, and (2) the first-principles high accuracy chemical network we are developing for the production and destruction of hydrogen (iso)cyanide in space.

  15. Chemistry Department Colloquium

    "Discovering Emergent Phenomena in Catalysis Through Large Scale Ab Initio Molecular Dynamics Simulations"

    Presented by Roger Rousseau, Pacific Northwest National Laboratory

    Tuesday, May 29, 2018, 11 am
    Hamilton Seminar Room, Bldg. 555

    Hosted by: Sanjaya Senanayake

    The current state of the art of electronic structure methods allows us to tackle model systems on the order of 100s to 1000s of atoms with suitable speed and efficiency to perform statistical mechanical sampling on millions of configurations. This has opened the door to using theoretical tools such as ab initio molecular dynamics (AIMD) combined with enhanced sampling techniques) to discover novel emergent phenomena that result from chemical complexity. Nowhere is this more needed than in catalysis, where models need to include support materials, the catalysts, the reactants and products all at elevated temperature and pressures. In this context, both global and local anharmonicities on the potential energy surface can lead to unexpected phenomena that can be discovered through large scale simulation yet are often not accounted for in current theoretical studies. This will be illustrated with examples drawn from the chemistry of metal particles on reducible supports [1-3], Brønsted acid chemistry in confined spaces [4] and reactivity at solid-liquid interfaces [5,6]. In the context of metal particles supported on reducible metal oxides (such as TiO2, CeO2 and RuO2), we have found that there is a strong coupling between the redox state of the support and the redox properties of the nanoparticle [1,2] such that unique catalytic processes can occur including: Redox state dependent reaction energies [2,3]; Formation of transient single atoms, which are themselves catalytic [1,3]; For prototypical reactions such as CO oxidation, a complex mechanistic landscape where catalysis can occur by competing mechanisms involving both the nanoparticle and single atom sites at the same time. Similar methods have been used to investigate the confinement effect in zeolite [4] and understand the free energetics of acid catalysis in confined media. It is shown that due to the large anharmonic effects associated with molecules, such as ethanol, interacting with the walls of a s

  16. HET/RIKEN Lunch Seminar

    "Quantum Simulation from Quantum Chemistry to Quantum Chromodynamics"

    Presented by Peter Love, Tufts

    Thursday, May 10, 2018, 12:30 pm
    Building 510, Room 2-160

    Hosted by: Mattia Bruno and Enrico Rinaldi

    Quantum simulation proposes to use future quantum computers to calculate properties of quantum systems. In the context of chemistry, the target is the electronic structure problem: determination of the electronic energy given the nuclear coordinates of a molecule. Since 2006 we have been studying quantum approaches to quantum chemical problems, and such approaches must face the challenges of high, but fixed, precision requirements, and fermion antisymmetry. I will describe several algorithmic developments in this area including improvements upon the Jordan Wigner transformation, alternatives to phase estimation, adiabatic quantum computing approaches to the electronic structure problem, methods based on sparse Hamiltonian simulation techniques and the potential for experiments realizing these algorithms in the near future. I will also briefly review work by others on the analog and digital simulation of lattice gauge theories using quantum simulators.

  17. Condensed-Matter Physics & Materials Science Seminar

    "Chemistry beyond the crystal- advanced Fourier techniques"

    Presented by Simon Kimber, Oak Ridge National Laboratory

    Monday, April 30, 2018, 1:30 pm
    ISB Bldg. 734 Conf. Rm. 201 (upstairs)

    Hosted by: Ian Robinson

    Chemical crystallography nowadays makes structure determination and refinement trivial. However, advances in x-ray and neutron sources mean that we should revisit some of the basic assumptions that shape our experiments. For example, most chemical reactivity in e.g. catalysis, self-assembly etc, occurs in the solution phase. Why are we as crystallographers then wedded to the solid state? In this presentation, I will show how total scattering can be used to determine changes in cluster structure during photochemical reactions and to probe the role of the solvent in 'magic size' cluster formation. I will then describe how neutron scattering techniques can be used to challenge another basic assumption- the static approximation in total scattering. We have successfully applied so-called 'dynamic-PDF' techniques to simple chalcogenide materials. This allows to determine the time scale on which local distortions appear, providing insight into the role of highly anharmonic phonons in e.g. phase change and thermoelectric materials. Time allowing, I will also provide a short update on progress at ORNL, including the upcoming restart of the SNS, and new instrumentation for diffraction, total and diffuse scattering.

  18. Center for Functional Nanomaterials Seminar

    "Electrocatalysis: From nanoelectrochemistry to materials design"

    Presented by Professor Dr. Wolfgang Schuhmann, Ruhr-Universität Bochum, Analytical Chemistry and Center for Electrochemical Sciences (CES), Germany

    Friday, April 27, 2018, 11 am
    Bldg 735, CFN, Seminar Room 2nd Floor

    Hosted by: Huolin Xin

  19. Chemistry Department Seminar

    "Spectroscopy and Diabatization: Turning the GMH Method Upside Down to Study Butadiene"

    Presented by Robert Cave, Harvey Mudd College

    Friday, April 27, 2018, 11 am
    Room 300, 3rd Floor, Chemistry Bldg. 555

    Hosted by: John Miller

    The spectroscopy of the low-lying singlet states of butadiene has been a vexing problem for theorists for over forty years. The positions of the lowest-lying singlet states at the ground state geometry are something of a methodological Rorschach test and the planar stationary points of these states have seen modest attention. Important work has been done on the ultrafast dynamics of butadiene following excitation to the bright 11Bu but these studies are often forced to use simple wavefunctions that may lead to exaggerated couplings. We present new simulation results of its electronic spectrum based on Equations of Motion Coupled Cluster Theory in large basis sets using a vibronic coupling model involving many vibrational modes. We investigate the sensitivity of the results to the choice of vibronically-coupled states and test the dependence of the results on vertical excitation energies. We believe that butadiene should be considered somewhat less vexing than it has been before and our results can be used as a starting point for accurate explorations of its short-time excited state dynamics.

  20. Chemistry Department Seminar

    "In situ analysis of Ru-based catalysts under water oxidation conditions"

    Presented by Yulia Pushkar, Purdue University

    Tuesday, February 27, 2018, 10 am
    Room 300, 3rd Floor, Chemistry Bldg. 555

    Hosted by: Dmitry Polyansky

    Realization of artificial photosynthesis carries the promise of cheap and abundant energy. The water molecule is an ideal source of electrons and protons for fuel forming reactions, but the chemical complexity of water splitting makes practical realization challenging. To advance the catalyst's rational design, detailed information on the structure of the catalyst under reaction conditions and mechanisms of O-O bond formation are required. Here, we used a combination of EPR, freeze quench and stopped flow spectroscopy with ms-s time resolution, X-ray absorption spectroscopy (XAS), Resonance Raman (RR) and DFT to follow in situ catalyst dynamic under conditions of water oxidation.1-3 Two representative Ru –based catalysts were analyzed: [RuII(NPM)(4-pic)2(H2O)]2+ and [RuII(pic)2(dpp)]2+. First system has water coordinated to Ru center and forms [RuIV(NPM)(4-pic)2=O]2+ upon oxidation. This intermediate undergoes fast dynamics (on few sec time scale) of oxygen atom transfer from the RuIV=O oxo species to uncoordinated nitrogen of the NPM ligand. NPM ligand modification occurs on the time scale of catalyst activation and results in [RuIII(NPM-NO)(4-pic)2(H2O)]3+ and [RuIII(NPM-NO,NO)(4-pic)2]3+ complexes with unique EPR signals. [RuII(pic)2(dpp)]2+ complex was proposed to activate via formation of the 7-coordinate [RuV=O(pic)2(dpp)]3+ species. We report the first detection of the ligand protected 7-coordinate species in catalytic mixtures by combination of the spectroscopic techniques. Over a few minutes this intermediate transfers oxygen from the RuV=O group to a pyridyl nitrogen of the dpp ligand. This reaction proceeds twice resulting in the dpp-di-N-oxide ligand. This ligand modification results in the catalyst activation. [Ru(bda)(pic)2] complex is also proposed to activate via formation of 7-coordinate [RuV=O(bda)(pic)2]+ intermediate which is highly reactive in solution via radical coupling pathway. Site isolation of the catalyst on the electrode

  21. NSLS-II Friday Lunchtime Seminar Series

    "Using X-ray Fluorescence Microprobe to Elucidate the Chemistry of Trace Elements in Soils and Plants"

    Presented by Ryan Tappero, NSLS-II

    Friday, February 23, 2018, 12 pm
    NSLS-II Bldg. 743 Rm 156

    Hosted by: M. Abeykoon, S. Chodankar, B. Ocko, T. Tanabe, J. Thieme

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