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NESM TAG Meeting Notes
March 2015 NESM TAG Notes related to 1) Structure surface representation, 2) Structure-fluid coupling algorithm, 3) Coupled time integration scheme, 4) Coupling data exchange API, 5) Portability across platforms and builds, and 6) Testing and verification.
Solar cell comprising a plasmonic back reflector and method therefor
A method for forming a solar cell having a plasmonic back reflector is disclosed. The method includes the formation of a nanoimprinted surface on which a metal electrode is conformally disposed. The surface structure of the nanoimprinted surface gives rise to a two-dimensional pattern of nanometer-scale features in the metal electrode enabling these features to collectively form the plasmonic back reflector.
Method of forming macro-structured high surface area transparent conductive oxide electrodes
A method of forming a high surface area transparent conducting electrode is provided that includes depositing a transparent conducting thin film on a conductive substrate, where the transparent conducting thin film includes transparent conductive particles and a solution-based transparent conducting adhesive layer which serves to coat and bind together the transparent conducting particles, and heat treating the transparent conducting adhesion layer on the conductive substrate, where an increased surface area transparent conducting electrode is formed.
Electrode structures and surfaces for Li batteries
This invention relates to methods of preparing positive electrode materials for electrochemical cells and batteries. It relates, in particular, to a method for fabricating lithium-metal-oxide electrode materials for lithium cells and batteries. The method comprises contacting a hydrogen-lithium-manganese-oxide material with one or more metal ions, preferably in an acidic solution, to insert the one or more metal ions into the hydrogen-lithium-manganese-oxide material; heat-treating the resulting product to form a powdered metal oxide composition; and forming an electrode from the powdered metal oxide composition.
CHARACTERIZATION OF THE B / SI SURFACE ELECTRONIC STRUCTURES.
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Direct detection of chemisorbed hydrogen on metal hydride and structural material surfaces using low energy ion scattering.
Abstract not provided.
Imaging system and method for enhanced visualization of near surface vascular structures
A sub-dermal structure visualization system and method is disclosed. The system may use an illumination module including: a near-infrared (NIR) light source adapted to substantially uniformly illuminate an imaged area including sub-dermal regions thereof with NIR light; and a first optical system including at least one optical element for controlling at least one of spectral and polarization properties of the NIR light prior to illuminating the imaged area. An imaging module rejects unwanted signals from an imaged area while passing desired optical signals that are to be received by an image acquisition module. The desired optical signals can comprise a vein visualization signal to assist in visualizing a vascular structure below a skin layer of a patient.
Influence of Surfaces and Structural Defects on the Electrochemical Properties of MnO2 in Rechargeable Zn/MnO2 Batteries.
Abstract not provided.
Surface Reconstructions of Metal Oxides and the Consequences on Catalytic Chemistry
Catalysts are inherently vital in nature, as they respond to the environment by changing their local and extended structures. Surface reconstruction is among such dynamic behaviors of catalysts and greatly affects the physical, chemical, and electronic properties of catalysts and consequently the catalytic performances. Thus, understanding the nature of the catalytic sites of the reconstructed surfaces is essential for establishing the structure–catalysis relations and has attracted much interest in catalysis research. Knowledge of the reconstruction of metal oxides has been quite limited in comparison to that of metal surfaces because the nature of oxide surfaces is generally more complex. However, significant progress has been made in recent years in oxide surfaces thanks to the advances in the ability to synthesize model oxide nanocrystals and to characterize the surface reconstruction behaviors under in situ and operando conditions with advanced spectroscopy and microscopy aided by computational modeling. In this Perspective, such advances in understanding the surface reconstruction behaviors of metal oxide nanoshapes and thin films with well-defined surface structures under as-synthesized, various pretreatment, and reaction environments will be summarized, and the catalytic consequences of these reconstructions will be highlighted. The results from these studies clearly show that the combination of model oxides and in situ/operando investigations is imperative in shaping the fundamental understanding of the dynamic reconstructions of oxide surfaces. Yet, it is still difficult to study the surface reconstructions of oxide catalysts with meaningful temporal and spatial resolution under operating conditions. Future opportunities are discussed on how to address the challenges and eventually help to design more efficient catalysts by taking advantages of the surface reconstructions.
Alkaline salt-promoted construction of hydrophilic and nitrogen deficient graphitic carbon nitride with highly improved photocatalytic efficiency
Graphitic carbon nitride (g-C 3 N 4 ) possesses fascinating merits, but its practical applications are limited by the inferior properties of limited visible-light sorption, rapid recombination of photo-excited charge carriers and low electrical conductivity. Introduction of N-defects is an efficient approach to tune its optical properties, but strategies capable of creating abundant vacancies and simultaneously maintaining the highly crystalline architecture are still limited and highly desired. In this work, a facile construction methodology was demonstrated to afford g-C 3 N 4 with abundant N vacancies, high crystallinity, a hydrophilic surface structure, a small particle size, and an increased surface area under neat and mild conditions. Furthermore, the essence of our approach lies in the treatment of the bulk g-C 3 N 4 precursor with an alkaline salt (LiN(SiMe 3 ) 2 ) with a low melting point, moderate nucleophilicity, and easy removal procedures. The unique structural properties of the afforded ND-g-C 3 N 4 allow for a significantly redshifted absorption edge and enhanced charge carrier separation, leading to superior photocatalytic hydrogen evolution performance three times that obtained by pristine g-C 3 N 4 . The modification strategy developed herein sheds light on the fabrication of g-C 3 N 4 -based materials with improved photocatalytic efficiency via efficient introduction of N defects, variation of the surface structure, and retention of the high crystallinity.
Catalytic properties of intermetallic platinum-tin nanoparticles with non-stoichiometric compositions
Abstract not provided
Single Crystals of Vanadium Oxides as a Lens for Understanding Structural and Electronic Phase Transformations, Ion Transport, Chemo-Mechanical Coupling, and Electrothermal Neuronal Emulation
Vanadium oxides cystallize in a diverse array of structures and compositions arising from the redox versatility of vanadium, variable covalency of V−O bonds, and myriad coordination geometries. Their open frameworks present abundant interstitial sites that enable insertion of guest-ions. In such compounds, V3d electron and spin localization and disorder couple strongly to structural preferences. The rich structural diversity manifests as a “rugged” free energy landscape with multiple interconvertible polymorphs. Such a landscape sets up structural, electronic, and magnetic transitions that underpin the promise of these materials as ion-insertion battery electrodes; compact primitives for brain-inspired computing, and heterogeneous catalysts. Here, we examine the structural and compositional diversity, electronic instabilities, defect dynamics, structure transformations, mechanical properties, and surface structure of vanadium oxides using single crystals as a distinctive lens. Single crystals enable the measurement of structure−function correlations without the ensemble and orientational averaging inevitable in polycrystalline materials. Their well-defined surfaces further enable examination of facet-dependent reactivity toward molecular adsorbates, ion fluxes, and lattice (mis)matched solids. We provide a comprehensive account of vanadium-oxide single-crystal studies, from delineation of common structural motifs to single-crystal growth techniques, topochemical modification strategies, mechanisms underpinning electronic instabilities, and implementation as electrothermal neurons and battery electrode materials.
Sequence-Dependent Structure/Function Relationships of Catalytic Peptide-Enabled Gold Nanoparticles Generated under Ambient Synthetic Conditions
Peptide-enabled nanoparticle (NP) synthesis routes can create and/or assemble functional nanomaterials under environmentally friendly conditions, with properties dictated by complex interactions at the biotic/abiotic interface. Manipulation of this interface through sequence modification can provide the capability for material properties to be tailored to create enhanced materials for energy, catalysis, and sensing applications. Fully realizing the potential of these materials requires a comprehensive understanding of sequence-dependent structure/function relationships that is presently lacking. In this work, the atomic-scale structures of a series of peptide-capped Au NPs are determined using a combination of atomic pair distribution function analysis of high-energy X-ray diffraction data and advanced molecular dynamics (MD) simulations. The Au NPs produced with different peptide sequences exhibit varying degrees of catalytic activity for the exemplar reaction 4-nitrophenol reduction. The experimentally derived atomic-scale NP configurations reveal sequence-dependent differences in structural order at the NP surface. Replica exchange with solute-tempering MD simulations are then used to predict the morphology of the peptide overlayer on these Au NPs and identify factors determining the structure/catalytic properties relationship. We show that the amount of exposed Au surface, the underlying surface structural disorder, and the interaction strength of the peptide with the Au surface all influence catalytic performance. A simplified computational prediction of catalytic performance is developed that can potentially serve as a screening tool for future studies. Our approach provides a platform for broadening the analysis of catalytic peptide-enabled metallic NP systems, potentially allowing for the development of rational design rules for property enhancement.
Surface buckling of black phosphorus: Determination, origin, and influence on electronic structure
The surface structure of black phosphorus materials is determined using surface-sensitive dynamical microspot low energy electron diffraction ( μ LEED ) analysis using a high spatial resolution low energy electron microscopy (LEEM) system. Samples of (i) crystalline cleaved black phosphorus (BP) at 300 K and (ii) exfoliated few-layer phosphorene (FLP) of about 10 nm thickness which were annealed at 573 K in vacuum were studied. In both samples, a significant surface buckling of 0.22 Å and 0.30 Å, respectively, is measured, which is one order of magnitude larger than previously reported. As direct evidence for large buckling, we observe a set of (for the flat surface forbidden) diffraction spots. Using first-principles calculations, we find that the presence of surface vacancies is responsible for the surface buckling in both BP and FLP, and is related to the intrinsic hole doping of phosphoresce materials previously reported.
Pathways for Ethanol Dehydrogenation and Dehydration Catalyzed by Ceria (111) and (100) Surfaces
We have performed computations to better understand how surface structure affects selectivity in dehydrogenation and dehydration reactions of alcohols. Ethanol reactions on the (111) and (100) ceria surfaces were studied starting from the dominant surface species, ethoxy. We used DFT (PBE+U) to explore reaction pathways leading to ethylene and acetaldehyde and calculated estimates of rate constants employing transition state theory. To assess pathway contributions, we carried out kinetic analysis. Our results show that intermediate and transition state structures are stabilized on the (100) surface compared to the (111) surface. Formation of acetaldehyde over ethylene is kinetically and thermodynamically preferred on both surfaces. Our results are consistent with temperature programmed surface reaction and steady-state experiments, where acetaldehyde was found as the main product and evidence was presented that ethylene formation at higher temperature originates from changes in adsorbate and surface structure.