6 research outputs found

    DataSheet1_Designed NiMoC@C and NiFeMo2C@C core-shell nanoparticles for oxygen evolution in alkaline media.pdf

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    Electrochemical water splitting is one of the most promising and clean ways to produce hydrogen as a fuel. Herein, we present a facile and versatile strategy for synthesizing non-precious transition binary and ternary metal-based catalysts encapsulated in a graphitic carbon shell. NiMoC@C and NiFeMo2C@C were prepared via a simple sol-gel based method for application in the Oxygen Evolution Reaction (OER). The conductive carbon layer surrounding the metals was introduced to improve electron transport throughout the catalyst structure. This multifunctional structure showed synergistic effects, possess a larger number of active sites and enhanced electrochemical durability. Structural analysis indicated that the metallic phases were encapsulated in the graphitic shell. Experimental results demonstrated that the optimal core-shell material NiFeMo2C@C exhibited the best catalytic performance for the OER in 0.5 M KOH, reaching a current density of 10 mA cm-2 at low overpotential of 292 mV for the OER, superior to the benchmark IrO2 nanoparticles. The good performances and stability of these OER electrocatalysts, alongside an easily scalable procedure makes these systems ideal for industrial purposes.</p

    Manipulation of Phase and Microstructure at Nanoscale for SiC in Molten Salt Synthesis

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    Silicon carbide (SiC) is a compound with strong covalent bonding, which gives its high mechanical strength and oxidation resistance, but also hinders its synthesis under moderate conditions. Herein, a facile route is presented for the synthesis of SiC nanomaterials from simple and abundant raw materials in an inorganic molten salt (MS). With this route, we are able to synthesis nanoscale 3C-SiC and 2H-SiC in a controlled manner, where the choice of cubic or hexagonal structure is coupled to nanocrystal size. By selection of the starting materials and tuning of the synthesis conditions, the MS-derived SiC can be isolated as nanoparticles (NPs), porous SiC/C composites with small primary crystals (2‚Äď4 nm), and as nanospheres. We also show that the SiC nanostructures are active for electrochemical hydrogen evolution reaction, and the activity can be remarkably improved by loading Pt (NPs) onto the structure

    Titanium Nitride-Nickel Nanocomposite as Heterogeneous Catalyst for the Hydrogenolysis of Aryl Ethers

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    Lignin from biomass can become a sustainable source of aromatic compounds. Its depolymerization can be accomplished through hydrogenolysis, although the development of catalysts based on cheap and abundant metals is lacking. Herein, a sustainable composite based on titanium nitride and nickel is synthesized and employed as catalyst for the hydrogenolysis of aryl ethers as models for lignin. The catalytic activity of the new material during hydrogenation reactions is proven to be superior to that of either component alone. In particular, different aryl ethers could be efficiently converted under relatively mild conditions into aromatic compounds and cycloalkanes within minutes

    Mo and W Carbide: Tunable Catalysts for Liquid Phase Conversion of Alcohols

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    The application of Mo and W carbide (Mo<sub>2</sub>C and WC respectively) in the liquid phase oxidation of benzyl alcohol has been presented. Mo<sub>2</sub>C and WC are, indeed, considered among the most suitable candidates to replace noble metals for oxidation reactions because of their well recognized Pt- and Ru-like behavior, respectively. The good activity of metal carbides and their low cost, compared with noble metals, makes them appealing systems, worth of further investigations. Moreover, the peculiar tunability of the selectivity of these catalysts depending on the reaction medium has been highlighted

    Iron Nitride and Carbide: from Crystalline Nanoparticles to Stable Aqueous Dispersions

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    Iron nitride and carbide nanoparticles were synthesized using iron oxide particles as template. They were furthermore dispersed in aqueous solution via stabilization with a poly­(ionic liquid). They provide a great potential combining a high saturation magnetization with low toxicity compared to the iron based compounds that are currently used in several applications such as cell-sorting and hyperthermia or as contrast enhancers for magnetic resonance imaging. We here present a sustainable and green procedure to synthesize iron nitride and carbide by resorting to the variety of iron oxide template nanoparticles. In this way the shape and the size can be precisely controlled and tuned within the nanometer range. During calcination, urea enables to control the composition of the product material, whereas a biopolymer agar protects the particles from agglomeration. We dispersed the particles in water by using poly­(1-ethyl-3-vinylimidazolium bromide) as stabilizing agent. Magnetic measurements of the converted particles show that particles with a diameter of 18 nm are located at the border of superparamagnetic and ferromagnetic behavior. As expected after conversion the saturation magnetization of the particles was notably increased. The herein presented synthetic approach can be applied to other metals and has thus the potential to be important for the synthesis of nitrides and carbides in general

    Structure‚ÄďProperties Correlation in Si Nanoparticles by Total Scattering and Computer Simulations

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    High-energy synchrotron X-ray diffraction coupled to atomic pair distribution function analysis and computer simulations is used to determine the atomic-scale structure of silicon (Si) nanoparticles obtained by two different synthetic routes. Results show that Si nanoparticles may have significant structural differences depending on the synthesis route and surface chemistry. In this case, one method produced Si nanoparticles that are highly crystalline but surface oxidized, whereas a different method yields organic ligand-passivated nanoparticles without surface oxide but that are structurally distorted at the atomic scale. Particular structural features of the oxide-free Si nanoparticles such as average first coordination numbers, length of structural coherence, and degree of local distortions are compared to their optical properties such as photoluminescence emission energy, quantum yield, and Raman spectra. A clear structure‚Äďproperties correlation is observed indicating that the former may need to be taken into account when considering the latter