Hydrogen evolution was performed in KOH and H2SO4 electrolytes using α-Mo2C and γ-Mo2N synthesized by the ‘urea glass’ route. α-Mo2C shows excellent performance especially in KOH.

A simple, inexpensive, and versatile route for the synthesis of metal nitrides and carbides (such as Mo2N, Mo2C, W2N and WC) nanoparticles was set up. For the first time, metal carbides were obtained using urea as carbon-source. MoCl5 and WCl4 are in a first step contacted with alcohols and an appropriate amount of urea to form a polymer-like, glassy phase, which acts as the starting product for further conversions. Just by heating this phase it was possible to prepare either molybdenum and tungsten nitrides or carbides simply by changing the metal precursor/urea molar ratio. In this procedure, urea plays a double role as a nitrogen/carbon source and stabilizing agent (necessary for the nanoparticle dispersion). Molybdenum and tungsten nitride and carbides synthesized are almost pure and highly crystalline. Sizes estimated by WAXS range around 20 and 4 nm in diameter for Mo and W nitrides or carbides, respectively. The specific surface area was found between 10 and 80 m2/g, depending on the metal and the initial ratio of metal precursor to urea.

An easy way to produce several metal nitrides and metal carbides at relatively low temperature (800°C) using simple and mainly nontoxic precursor is presented. The procedure has been shown to be rather general and it was possible to synthesize TiN, VN, NbN, GaN, Mo 2 N, W 2 N, CrN, NbC(N), TiC(N), WC, Mo 2 C, and Cr 3 C 2 nanoparticles using urea or close derivatives as both nitrogen or carbon source and the growth controlling system. In every case, a homogeneous gel-like starting product has been formed that is converted by calcination into the corresponding metal nitride or metal carbide (including mixed species), without any preliminary treatments or further purifications. Samples were characterized by XRD, TEM, SEM, EA, and BET, and the products were shown to be well-defined and rather homogeneous.

Efficient synthetic routes are continuously pursued for graphene in order to implement its applications in different areas. However, direct conversion of simple monomers to graphene through polymerization in a scalable manner remains a major challenge for chemists. Herein, a molten-salt (MS) route for the synthesis of carbon nanostructures and graphene by controlled carbonization of glucose in molten metal chloride is reported. In this process, carbohydrate undergoes polymerization in the presence of strongly interacting ionic species, which leads to nanoporous carbon with amorphous nature and adjustable pore size. At a low precursor concentration, the process converts the sugar molecules (glucose) to rather pure few-layer graphenes. The MS-derived graphenes are strongly hydrophobic and exhibit remarkable selectivity and capacity for absorption of organics. The methodology described may open up a new avenue towards the synthesis and manipulation of carbon materials in liquid media.

No abstract

In this contribution a template-free preparation of mesoporous graphitic carbon nanostructures with high electric conductivity is presented, using ionic liquid monomers or poly(ionic liquid) polymers as carbon precursors. The carbonization was performed in the presence of FeCl2 at temperatures between 900 and 1000 °C. It was found that FeCl2 plays a key role in controlling both the chemical structure and the texture morphology of the graphitization process. A detailed investigation on the carbonization process demonstrated that 900 °C is a threshold temperature where a synergistic formation process enables the development of the superior physical properties, such as large surface area and low resistance. The as-synthesized carbon products are graphitic, mesoporous, and highly conductive, as proven by XRD and TEM characterizations and conductivity measurements. Via an acid etching process, iron and iron carbide nanoparticles, the remainder of the primary catalyst, can be removed, leaving pure mesoporous carbon nanomaterials with a comparably well developed graphitic structure. Without demand for any template, this method is facile and easy to scale up and might contribute to the wide range of applications of carbon nanostructures.

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.

Metal-boron alloys contain a boron covalent framework providing typical high chemical, mechanical, and thermal stability, which allows important applications, for example, for diborides (NbB 2 ) and hexaborides (CaB 6 ) as refractory materials.[1] New properties also arise from alloying; a prime example is the superconductivity of magnesium diboride, which exhibits the highest critical temperature (39 K) among classical superconductors.[2] Hexaborides are also relevant because of their field emission properties [3] and their potential for thermoelectricity (CeB 6 ).[4] Moreover, transition-metal borides are drawing attention as efficient (de)hydrogenation catalysts that can accelerate, for instance, emission of hydrogen from ammonia-borane or borohydrides within energyharnessing devices based on hydrogen technology.[5] Applications in hyperthermia, information storage, thermoelectricity, and catalysis would benefit from scaling down to the nanometer range, which could bring, as for all nanomaterials, modified, enhanced, and even novel properties that arise from the finite particle size. To date, only a few nanostructured borides have been reported. This paucity arises mainly because M-B systems are typically synthesized at high temperatures above 1100 8C.[6] Nanoscale materials have been obtained at lower temperatures (25-100 8C), but at the expense of crystallinity and stability, and such approaches yield pyrophoric compounds without applicability.[7] The scarce reported procedures for nanostructured crystalline systems rely on physical [5,8] or chemical methods, [9] and none of them is demonstrated to be generally applicable to the wide and rich family of borides. Moreover, the majority of crystalline metal borides has not yet been approached at the nanoscale, such as hard (HfB 2 ) or ultrahard (MoB 4 ) materials, catalysts, and ferromagnetic compounds (FeB). The development of a reliable, versatile, and general synthesis procedure towards such systems is therefore still eagerly demanded.One requirement to obtain such nanostructures is the use of relatively mild temperatures, which are still high enough to trigger crystallization but low enough to avoid excessive grain growth, ideally in the range 500-900 8C. Then, development of a solution route instead of standard solid-state reactions may contribute to full kinetic accessibility of the reaction space, which includes control of nanocrystal size and shape. [10] Because of the thermal instability of organic solvents in such conditions, we turned to inorganic molten salts, which are readily available and safe to apply at the targeted temperatures.Herein we present the use of such salt melts for the first general synthesis of metal boride nanocrystals. The method is based on a one-pot ionothermal process which is simple and relies on medium temperature, atmospheric pressure, and environmentally friendly solvents. Applicability to a wide range of compounds, formation of novel nanostructures, and control over the nanocrystal size and the material texture are demons...