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2D catalyst

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https://www.readbyqxmd.com/read/28208240/application-toward-confocal-full-field-microscopic-x-ray-absorption-near-edge-structure-spectroscopy
#1
Pieter Tack, Bart Vekemans, Brecht Laforce, Jennifer Rudloff-Grund, Willinton Y Hernández, Jan Garrevoet, Gerald Falkenberg, Frank Brenker, Pascal Van Der Voort, Laszlo Vincze
Using X-ray absorption near edge structure (XANES) spectroscopy, information on the local chemical structure and oxidation state of an element of interest can be acquired. Conventionally, this information can be obtained in a spatially resolved manner by scanning a sample through a focused X-ray beam. Recently, full-field methods have been developed to obtain direct 2D chemical state information by imaging a large sample area. These methods are usually in transmission mode, thus restricting the use to thin and transmitting samples...
February 7, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28195130/robust-microscale-superlubricity-under-high-contact-pressure-enabled-by-graphene-coated-microsphere
#2
Shu-Wei Liu, Hua-Ping Wang, Qiang Xu, Tian-Bao Ma, Gui Yu, Chenhui Zhang, Dechao Geng, Zhiwei Yu, Shengguang Zhang, Wenzhong Wang, Yuan-Zhong Hu, Hui Wang, Jianbin Luo
Superlubricity of graphite and graphene has aroused increasing interest in recent years. Yet how to obtain a long-lasting superlubricity between graphene layers, under high applied normal load in ambient atmosphere still remains a challenge but is highly desirable. Here, we report a direct measurement of sliding friction between graphene and graphene, and graphene and hexagonal boron nitride (h-BN) under high contact pressures by employing graphene-coated microsphere (GMS) probe prepared by metal-catalyst-free chemical vapour deposition...
February 14, 2017: Nature Communications
https://www.readbyqxmd.com/read/28168251/dimensional-heterostructures-of-1d-cds-2d-znin2s4-composited-with-2d-graphene-designed-synthesis-and-superior-photocatalytic-performance
#3
Qingyong Tian, Wei Wu, Jun Liu, Zhaohui Wu, Weijing Yao, Jin Ding, Changzhong Jiang
The development of photocatalysts with superior photoactivity and stability for the degradation of organic dyes is very important for environmental remediation. In this study, we have presented a multidimensional (1D and 2D) structured CdS/ZnIn2S4/RGO photocatalyst with superior photocatalytic performance. The CdS/ZnIn2S4 helical dimensional heterostructures (DHS) were prepared via a facile solvothermal synthesis method to facilitate the epitaxial growth of 2D ZnIn2S4 nanosheets on 1D CdS nanowires. Ultrathin 2D ZnIn2S4 nanosheets have grown uniformly and perpendicular to the surface of 1D CdS nanowires...
February 7, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28159455/application-of-1-h-and-27-al-magic-angle-spinning-solid-state-nmr-at-60khz-for-studies-of-au-and-au-ni-catalysts-supported-on-boehmite-alumina
#4
Piotr Paluch, Natalia Potrzebowska, Agnieszka M Ruppert, Marek J Potrzebowski
In this work for the first time we show the power of solid state NMR spectroscopy in structural analysis of alumina and catalysts supported on the alumina surface employing very fast (60kHz) magic angle spinning (MAS) technique. In the methodological part we demonstrate that under such MAS condition, cross-polarization (CP) from proton to aluminum is an efficient process when a very weak (27)Al RF field is applied. The mechanism of CP transfer and the Hartmann-Hahn (H-H) matching conditions were tested for (27)Al RF fields equal to 3...
January 26, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28151677/interferometric-2d-sum-frequency-generation-spectroscopy-reveals-structural-heterogeneity-of-catalytic-monolayers-on-transparent-materials
#5
Heather Vanselous, Ashley M Stingel, Poul B Petersen
Molecular monolayers exhibit structural and dynamical properties that are different from their bulk counterparts due to their interaction with the substrate. Extracting these distinct properties is crucial for a better understanding of processes such as heterogeneous catalysis and interfacial charge transfer. Ultrafast nonlinear spectroscopic techniques such as 2D infrared (2D IR) spectroscopy are powerful tools for understanding molecular dynamics in complex bulk systems. Here, we build on technical advancements in 2D IR and heterodyne-detected sum frequency generation (SFG) spectroscopy to study a CO2 reduction catalyst on nanostructured TiO2 with interferometric 2D SFG spectroscopy...
February 6, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28150913/facile-preparation-of-ultrathin-co3o4-nanocarbons-composites-with-greatly-improved-surface-activity-as-high-efficient-oer-catalyst
#6
Yu-Fei Song, Yanyan Chen, Jun Hu, Honglin Diao, Wenjing Luo
The efficient catalytic oxidation of water to dioxygen plays a significant role in solar fuel and artificial photosynthetic systems. It remains to be highly challenging to develop oxygen evolution reaction (OER) catalysts with high activity and low cost under mild conditions. Herein we report a new composite material based on ultrathin 2D Co3O4 nanosheets and reduced graphene oxides (rGO) via a one-pot hydrothermal strategy. The ultrathin Co3O4/rGO nanocomposite show superior stability under alkaline conditions and exhibit overpotential of 290 mV with a Tafel slope of 68 mA*dec-1, which is much smaller than that of bare Co3O4 catalyst...
February 2, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28145692/from-carbon-based-nanotubes-to-nanocages-for-advanced-energy-conversion-and-storage
#7
Qiang Wu, Lijun Yang, Xizhang Wang, Zheng Hu
Carbon-based nanomaterials have been the focus of research interests in the past 30 years due to their abundant microstructures and morphologies, excellent properties, and wide potential applications, as landmarked by 0D fullerene, 1D nanotubes, and 2D graphene. With the availability of high specific surface area (SSA), well-balanced pore distribution, high conductivity, and tunable wettability, carbon-based nanomaterials are highly expected as advanced materials for energy conversion and storage to meet the increasing demands for clean and renewable energies...
February 1, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28116372/rh-nanoparticles-supported-on-ultrathin-carbon-nanosheets-for-high-performance-oxygen-reduction-reaction-and-catalytic-hydrogenation
#8
Chong Lin, Guanghao Wu, Huiqin Li, Yanmin Geng, Gang Xie, Jianhui Yang, Bin Liu, Jian Jin
We reported a facile and scalable salt-templated approach to produce monodisperse Rh nanoparticles (NPs) on ultrathin carbon nanosheets with the assistance of calcination under inert gas. More importantly, in spite of the essentially poor ORR activity of Rh/C, the acquired Rh/C hybrid nanosheets display a comparable ORR activity to the optimal commercial Pt/C catalyst, which may be due to the extra-small size of Rh NPs and the 2D defect-rich amorphous carbon nanosheets that can facilitate the charge transfer and reactive surface exposure...
January 24, 2017: Nanoscale
https://www.readbyqxmd.com/read/28111867/separation-of-anti-phase-signals-due-to-parahydrogen-induced-polarization-via-2d-nutation-nmr-spectroscopy
#9
Utz Obenaus, Gerhard Althoff-Ospelt, Swen Lang, Robin Himmelmann, Michael Hunger
The present work introduces a novel method for the selective detection of (1) H NMR anti-phase signals caused by the pairwise incorporation of parahydrogen into olefins on noble-metal-containing catalysts. Via a two-dimensional (2D) nutation NMR experiment, the anti-phase signals of hyperpolarized (1) H nuclei are separated due to their double nutation frequency compared to that of thermally polarized (1) H nuclei. For demonstrating this approach, parahydrogen induced polarization (PHIP) was achieved via the hydrogenation of propene with parahydrogen on platinum-containing silica and investigated by in situ (1) H MAS NMR spectroscopy under continuous-flow conditions, that is, the hydrogenation reaction was performed inside the magnet of the NMR spectrometer...
January 23, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28079359/pristine-graphene-electrode-in-hydrogen-evolution-reaction
#10
Aozhen Xie, Ningning Xuan, Kun Ba, Zhengzong Sun
Graphene, the sp(2) carbonaceous two-dimensional (2D) material, is gaining more attention in recent electrochemical studies. However, this atomic thick electrode usually suffers with surface contamination and poor electrochemical endurance. To overcome the drawbacks, we developed a PMMA-assisted, flipped transfer method to fabricate the graphene electrode with pristine surface and prolonged lifetime in hydrogen evolution reaction (HER). The HER performances of the single-layer graphene (SLG) were evaluated on various insulating and conductive substrates, including SiO2, polymers, SLG, highly oriented pyrolytic graphite (HOPG), and copper...
January 24, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28079290/clamped-hybridization-chain-reactions-for-the-self-assembly-of-patterned-dna-hydrogels
#11
Jianbang Wang, Jie Chao, Huajie Liu, Shao Su, Lianhui Wang, Wei Huang, Itamar Willner, Chunhai Fan
DNA hydrogels hold great potential for biological and biomedical applications owing to their programmable nature and macroscopic sizes. However, most previous studies involve spontaneous and homogenous gelation procedures in solution, which often lack precise control. A clamped hybridization chain reaction (C-HCR)-based strategy has been developed to guide DNA self-assembly to form macroscopic hydrogels. Analogous to catalysts in chemical synthesis or seeds in crystal growth, we introduced DNA initiators to induce the gelation process, including crosslinked self-assembly and clamped hybridization in three dimensions with spatial and temporal control...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28060467/rapid-one-pot-preparation-of-large-freestanding-nanoparticle-polymer-films
#12
Yikai Xu, Magdalena P Konrad, Johann L Trotter, Colin P McCoy, Steven E J Bell
2D arrays of metal nanoparticles formed at liquid-liquid interfaces have been fixed in situ to a thin polymer support to create freestanding large (cm(2) ) composite films where the particles remain exposed rather than being trapped within the polymer. Applications of these flexible robust 2D nanoparticle arrays as sensors, thin film conductors, antimicrobial coatings, and dip-in catalysts are shown.
January 2017: Small
https://www.readbyqxmd.com/read/28045007/molecular-assembly-on-two-dimensional-materials
#13
Avijit Kumar, Kaustuv Banerjee, Peter Liljeroth
Molecular self-assembly is a well-known technique to create highly functional nanostructures on surfaces. Self-assembly on two-dimensional (2D) materials is a developing field driven by the interest in functionalization of 2D materials in order to tune their electronic properties. This has resulted in the discovery of several rich and interesting phenomena. Here, we review this progress with an emphasis on the electronic properties of the adsorbates and the substrate in well-defined systems, as unveiled by scanning tunneling microscopy...
January 3, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28044998/a-path-for-synthesis-of-boron-nitride-nanostructures-in-volume-of-arc-plasma
#14
Longtao Han, Predrag Krstić
We find a possible channel for direct nanosynthesis of boron-nitride (BN) nanostructures, including growth of BN nanotubes from a mixture of BN diatomic molecules by quantum-classical molecular dynamics simulations. No catalyst or boron nanoparticle is needed for this synthesis, however the conditions for the synthesis of each of the nanostructures, such as temperature and flux of the BN feedstock are identified and are compatible with the conditions in an electric arc at high pressure. We also find that BN nanostructures can be synthetized by feeding a boron nanoparticle by BN diatomic molecules, however if hydrogen rich molecules like NH3 or HBNH are used as a feedstock, two-dimensional nanoflake stable structures are formed...
January 3, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28032999/dynamic-flexibility-of-hydrogenase-active-site-models-studied-with-2d-ir-spectroscopy
#15
Peter A Eckert, Kevin J Kubarych
Hydrogenase enzymes enable organisms to use H2 as an energy source, having evolved extremely efficient biological catalysts for the reversible oxidation of molecular hydrogen. Small-molecule mimics of these enzymes provide both simplified models of the catalysis reactions and potential artificial catalysts that might be used to facilitate a hydrogen economy. We have studied two diiron hydrogenase mimics, μ-pdt-[Fe(CO)3]2 and μ-edt-[Fe(CO)3]2 (pdt = propanedithiolate, edt = ethanedithiolate), in a series of alkane solvents and have observed significant ultrafast spectral dynamics using two-dimensional infrared (2D-IR) spectroscopy...
January 12, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28029778/aqueous-exfoliation-of-transition-metal-dichalcogenides-assisted-by-dna-rna-nucleotides-catalytically-active-and-biocompatible-nanosheets-stabilized-by-acid-base-interactions
#16
Miguel Ayán-Varela, Óscar Pérez-Vidal, Juan I Paredes, José M Munuera, Silvia Villar-Rodil, María Díaz-González, César Fernández-Sánchez, Virgilia S Silva, Mónica Cicuéndez, Mercedes Vila, Amelia Martínez-Alonso, Juan M D Tascón
The exfoliation and colloidal stabilization of layered transition metal dichalcogenides (TMDs) in an aqueous medium using functional biomolecules as dispersing agents have a number of potential benefits toward the production and practical use of the corresponding two-dimensional materials, but such a strategy has so far remained underexplored. Here, we report that DNA and RNA nucleotides are highly efficient dispersants in the preparation of stable aqueous suspensions of MoS2 and other TMD nanosheets at significant concentrations (up to 5-10 mg mL(-1))...
January 11, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28001389/synthesis-and-characterization-of-0d-3d-copper-containing-tungstobismuthates-obtained-from-the-lacunary-precursor-na9-b-%C3%AE-biw9o33
#17
Kim D von Allmen, Henrik Grundmann, Anthony Linden, Greta R Patzke
The reaction of the lacunary polyoxometalate precursor Na9[B-α-BiW9O33]·19.5H2O with Cu(II) ions was explored in search of new economic ways to copper tungstobismuthates as interesting prototypes for water oxidation and reduction catalysts. The emerging series of new 0D-3D polyoxometalate architectures with distinct copper cores was structurally characterized. Na6Rb6[Cu3(H2O)3(BiW9O33)2] (Cu-4) and 3D-K6.56Cu0.43H2.20[(Cu3Cl)(K2.62Cu0.38(H2O)3)(B-α-BiW9O33)2]·13H2O (Cu-5) display a Cu3(H2O)3 core. The 2D representatives Na12[Cu2(H2O)4Cl2(BiW10O35)2] (Cu-1a), Na10[Cu2(H2O)6(BiW10O35)2] (Cu-1b), 2D-Na7K3Cu0...
January 3, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/27980992/transition-metal-promoted-v2co2-mxenes-a-new-and-highly-active-catalyst-for-hydrogen-evolution-reaction
#18
Chongyi Ling, Li Shi, Yixin Ouyang, Qian Chen, Jinlan Wang
Developing alternatives to precious Pt for hydrogen production from water splitting is central to the area of renewable energy. This work predicts extremely high catalytic activity of transition metal (Fe, Co, and Ni) promoted two-dimensional MXenes, fully oxidized vanadium carbides (V2CO2), for hydrogen evolution reaction (HER). The first-principle calculations show that the introduction of transition metal can greatly weaken the strong binding between hydrogen and oxygen and engineer the hydrogen adsorption free energy to the optimal value ≈0 eV by choosing the suitable type and coverage of the promoters as well as the active sites...
November 2016: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
https://www.readbyqxmd.com/read/27980990/high-performance-direct-methanol-fuel-cells-with-precious-metal-free-cathode
#19
Qing Li, Tanyuan Wang, Dana Havas, Hanguang Zhang, Ping Xu, Jiantao Han, Jaephil Cho, Gang Wu
Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt-based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol-tolerant cathodes must be developed before DMFC technologies become viable...
November 2016: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
https://www.readbyqxmd.com/read/27966713/high-intrinsic-catalytic-activity-of-two-dimensional-boron-monolayers-for-the-hydrogen-evolution-reaction
#20
Li Shi, Chongyi Ling, Yixin Ouyang, Jinlan Wang
Two-dimensional (2D) boron monolayers have been successfully synthesized on a silver substrate very recently. Their potential application is thus of great significance. In this work, we explore the possibility of boron monolayers (BMs) as electrocatalysts for the hydrogen evolution reaction (HER) by first-principles methods. Our calculations show that BMs are active catalysts for HER with nearly zero free energy of hydrogen adsorption, metallic conductivity and plenty of active sites in the basal plane. The effect of the substrate on HER activity is further assessed...
December 14, 2016: Nanoscale
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