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2D catalyst

Aozhen Xie, Ningning Xuan, Kun Ba, Zhengzong Sun
Graphene, the sp2 carbonaceous two dimensional (2D) material, is gaining more attentions 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 12, 2017: ACS Applied Materials & Interfaces
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
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
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 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 (STM)...
January 3, 2017: Nanotechnology
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
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
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
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
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)
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)
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
Meera Shete, Manjesh Kumar, Donghun Kim, Neel Rangnekar, Dandan Xu, Berna Topuz, Kumar Varoon Agrawal, Evguenia Karapetrova, Benjamin Stottrup, Shaeel Al-Thabaiti, Sulaiman Basahel, Katabathini Narasimharao, Jeffrey D Rimer, Michael Tsapatsis
Nanoscale crystal growth control is crucial for tailoring two-dimensional (2D) zeolites (crystallites with thickness less than two unit cells) and thicker zeolite nanosheets for applications in separation membranes and as hierarchical catalysts. However, methods to control zeolite crystal growth with nanometer precision are still in their infancy. Herein, we report solution-based growth conditions leading to anisotropic epitaxial growth of 2D zeolites with rates as low as few nanometers per day. Contributions from misoriented surface nucleation and rotational intergrowths are eliminated...
January 9, 2017: Angewandte Chemie
Ruizhi Wang, Patrick R Whelan, Philipp Braeuninger-Weimer, Stefan Tappertzhofen, Jack A Alexander-Webber, Zenas A Van Veldhoven, Piran R Kidambi, Bjarke S Jessen, Timothy Booth, Peter Bøggild, Stephan Hofmann
The mechanisms by which chemical vapor deposited (CVD) graphene and hexagonal boron nitride (h-BN) films can be released from a growth catalyst, such as widely used copper (Cu) foil, are systematically explored as a basis for an improved lift-off transfer. We show how intercalation processes allow the local Cu oxidation at the interface followed by selective oxide dissolution, which gently releases the 2D material (2DM) film. Interfacial composition change and selective dissolution can thereby be achieved in a single step or split into two individual process steps...
December 7, 2016: ACS Applied Materials & Interfaces
Jaegeon Ryu, Dongki Hong, Myoungsoo Shin, Soojin Park
Three-dimensional (3D) hyperporous silicon flakes (HPSFs) are prepared via the chemical reduction of natural clay minerals bearing metal oxides. Natural clays generally have 2D flake-like structures with broad size distributions in the lateral dimension and varied thicknesses depending on the first processing condition from nature. They have repeating layers of silicate and metal oxides in various ratios. When the clay mineral is subjected to a reduction reaction, metal oxide layers can perform a negative catalyst for absorbing large amounts of exothermic heat from the reduction reaction of the silicate layers with metal reductant...
November 22, 2016: ACS Nano
Lei-Lei Liu, Jing Chen, Cai-Xia Yu, Wen-Xing Lv, Hui-Ying Yu, Xiao-Qing Cui, Lin Liu
Nitrobenzene (NB) is a widespread and highly toxic organic pollutant in water, and consequently its detection and removal have attracted considerable attention. In the present study, we designed and synthesized a novel coordination polymer, [AgL0.5(NO3)]n (1), {L = 25,26,27,28-tetra[(3-pyridylmethyl)oxy]calix[4]arene}, from AgNO3 and a tetra-pyridyl-functionalized calix[4]arene ligand, which possessed a 2D network based on [Ag4L(NO3)4] units. The 1-modified glassy carbon electrode (1/GCE) exhibited good electrocatalytic activity toward the reduction of NB, offering the selective detection of NB in a wide linear range (1-2450 μM) and a low detection limit (0...
December 20, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Jingwen Zhu, Emilie-Laure Zins, Mohammad Esmaïl Alikhani
For over a decade, amine-borane has been considered as a potential chemical hydrogen vector in the context of a search for cleaner energy sources. When catalyzed by organometallic complexes, the reaction mechanisms currently considered involve the formation of β-BH agostic intermediates. A thorough understanding of these intermediates may constitute a crucial step toward the identification of ideal catalysts. Topological approaches such as QTAIM and ELF revealed to be particularly suitable for the description of β-agostic interactions...
December 2016: Journal of Molecular Modeling
Renhao Dong, Zhikun Zheng, Diana C Tranca, Jian Zhang, Naisa Chandrasekhar, Shaohua Liu, Xiaodong Zhuang, Gotthard Seifert, Xinliang Feng
Carbon electrocatalysts consisting of metal complexes such as MNx or MSx are promising alternatives to high-cost Pt catalysts for the hydrogen evolution reaction (HER). However, the exact HER active sites remain elusive. Here, molecular metal dithiolene-diamine (MS2 N2 , M=Co and Ni), metal bis(dithiolene) (MS4 ), and metal bis(diamine) (MN4 ) complexes were selectively incorporated into carbon-rich 2D metal-organic frameworks (2D MOFs) as model carbon electrocatalysts. The 2D MOF single layers, powders, and composites with graphene were thus prepared and showed definite active sites for H2 generation...
November 22, 2016: Chemistry: a European Journal
Gillian Collins, Eileen Armstrong, David McNulty, Sally O'Hanlon, Hugh Geaney, Colm O'Dwyer
This perspective reviews recent advances in inverse opal structures, how they have been developed, studied and applied as catalysts, catalyst support materials, as electrode materials for batteries, water splitting applications, solar-to-fuel conversion and electrochromics, and finally as photonic photocatalysts and photoelectrocatalysts. Throughout, we detail some of the salient optical characteristics that underpin recent results and form the basis for light-matter interactions that span electrochemical energy conversion systems as well as photocatalytic systems...
2016: Science and Technology of Advanced Materials
Courtney A Downes, Smaranda C Marinescu
Immobilization of metal complexes to electrode surfaces has emerged as an attractive strategy to combine homogeneous and heterogeneous catalysis. We recently reported the immobilization of cobalt dithiolene catalytic units via incorporation into extended one and two dimensional (1D and 2D) frameworks. We extend here this methodology to the formation of 1D nickel, iron, and zinc dithiolene coordination polymers based on benzene-1,2,4,5-tetrathiolate (BTT) frameworks and investigate their catalytic H2-evolving activities under fully aqueous conditions...
December 6, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Haiwei Guo, Bo Zhang, Zaojuan Qi, Changzhi Li, Jianwei Ji, Tao Dai, Aiqin Wang, Tao Zhang
Lignins isolated from representative hardwood, softwood, and grass materials were effectively hydrocracked to aromatics catalyzed by tungsten carbide over activated carbon (W2 C/AC). The effects of botanical species and fractionation methods on lignin structure and the activity of W2 C/AC were studied in detail. Gas permeation chromatography (GPC), FTIR, elemental analysis, and 2 D HSQC NMR showed that all the extracted samples shared the basic skeleton of lignin, whereas the fractionation method significantly affected the structure...
November 10, 2016: ChemSusChem
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