Abstract  Novel flower-like vanadium carbide (V8C7) hierarchical nanocrystals have been successfully synthesized in a large-scale hydrothermal process using a mixture of diethanolamine (HN(C2H4OH)(2), DEA) and V2O5 powder. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), selected-area electron diffraction (SAED) and energy-dispersive spectra (EDS). The results showed that flower-like products consist of very thin sheets with an average thickness of 10 nm and the nanosheets were a uniform single-crystalline V8C7 phase. It was found that reaction temperature and type of capping molecules have a crucial influence on the morphology of the products. A possible growth mechanism of the flower-like V8C7 hierarchical nanocrystals is proposed and discussed.

Abstract  Background and aim: Among various soils pollutants, heavy metals have great importance due to their toxicity and adverse effect on human health and environment. Therefore the aim of this study is comparing the concentration of heavy metals in surface soil of squares with high traffic at Kermanshah metropolises in 2015.

Materials and methods: For conducting this study, five high traffic area and five area as a reference soil were selected and from each location, five samples were collected. Finally a total of 50 point sample and 10 composite samples were obtained from these areas. The concentration of metals were evaluated based on the standard methods with ICP (Inductively Coupled Plasma) device.

Results: The results showed that the level of heavy metals in high traffic area and reference's soil samples were as bellow: Lead (Pb) > Nickel (Ni) > Chromium (Cr) > Vanadium (V) > Cadmium (Cd) > Selenium (Se). Also, the level of Cr, Cd and Ni in high traffic area were higher than references soil area.

Conclusion: According to the results, it is necessary to take some action for controlling the pollutants emission from mobile sources in high traffic area in order to reduce the heavy metals emission in the environment.

Abstract  Chemically demanding reductive conversions in biology, such as the reduction of dinitrogen to ammonia or the Birch-type reduction of aromatic compounds, depend on Fe/S-cluster-containing ATPases. These reductions are typically catalyzed by two-component systems, in which an Fe/S-cluster-containing ATPase energizes an electron to reduce a metal site on the acceptor protein that drives the reductive reaction. Here, we show a two-component system featuring a double-cubane [Fe8S9]-cluster [{Fe4S4(SCys)3}2(μ2-S)]. The double-cubane-cluster-containing enzyme is capable of reducing small molecules, such as acetylene (C2H2), azide (N3-), and hydrazine (N2H4). We thus present a class of metalloenzymes akin in fold, metal clusters, and reactivity to nitrogenases.

Abstract  Selected examples in V K-edge X-ray Absorption Near Edge Structure (XANES) analysis of a series of vanadium complexes containing imido ligands (possessing metal-nitiogen double bond) in toluene solution have been introduced, and their pre-edge and the edge were affected by then structures and nature of ligands. Selected results m exploring the oxidation states of the active species in ethylene dimerization/polymerization using homogeneous vanadium catalysts [consisting of (imido)vanadium(V) complexes and Al cocatalysts] by X-ray absorption spectroscopy (XAS) analyses have been introduced. It has been demonstrated that the method should provide more clear information concerning the active species in situ, especially by combination with the other methods (NMR and ESR spectra, X-ray ciystallographic analysis, and leaction chemistry), and should he powerful tool for study of catalysis mechanism as well as for the structural analysis in solution.

Abstract  Nitrogenase is the only known biological system capable of reducing N2 to NH3 , which is a critical component of bioavailable nitrogen fixation. Since the discovery of discrete iron-sulfur metalloclusters within the nitrogenase MoFe protein, synthetic inorganic chemists have sought to reproduce the structural features of these clusters in order to understand how they facilitate the binding, activation and hydrogenation of N2 . Through the decades following the initial identification of these clusters, significant progress has been made to synthetically replicate certain compositional and functional aspects of the biogenic clusters. Although much work remains to generate synthetic iron-sulfur clusters that can reduce N2 to NH3 , the insights borne from past and recent developments are discussed in this concept article.

Abstract  In order to develop a process for the separation of small amount of tungsten from macro amount of molybdenum, the selective loading of tungsten over molybdenum from sulfuric acid solution was investigated by ion exchange with TEVA resin. The separation factor between tungsten and molybdenum depended strongly on the equilibrium pH and tungsten concentration. A separation factor of 28 was obtained at an optimum condition. The loading behavior of tungsten into the resin fitted well with the Langmuir adsorption isotherm and the loading capacity for tungsten was determined. H2SO4 solution was more effective than NaOH solution as an eluent.

Abstract  This study investigated the methylene blue (MB) decolorization through heterogeneous UV-Fenton reaction catalyzed by V-Ti co-doped magnetites, with emphasis on comparing the contribution of V and Ti cations on improving the adsorption and catalytic activity of magnetite. In the well crystallized spinel structure, both Ti(4+) and V(3+) occupied the octahedral sites. Ti(4+) showed a more obvious effect on increasing specific surface area and superficial hydroxyl amount than V(3+) did, resulting in a significant improvement of the adsorption ability of magnetite to MB. The UV introduction greatly accelerated MB degradation. And magnetite with more Ti and less V displayed better catalytic activity in MB degradation through heterogeneous UV-Fenton reaction. The transformation of degradation products and individual contribution from vanadium and titanium on improving adsorption and catalytic activity of magnetite were also investigated. These new insights are of high importance for well understanding the interface interaction between contaminants and metal doped magnetites, and the environmental application of natural and synthetic magnetites.

Abstract  The oxygen transfer from the vanadium(v) complexes containing peroxo, oxo, and ozorficle ligands to electron-donating substrates (ethylene and vinyl methyl ether) was studied in the framework of the DFT with the M06 hybrid functional. The O atom of the ozonide fragment in the O3VO(eta-O2)(-) complex is transferred to the electron-donating substrates with lower energy expenses than the O atom of the peroxo group of the isomeric triperoxo complex, in spite of the fact that the presence of the peroxo group in the ozonide complexes stabilizes it favoring the formation of the V-Or bond according to the data of topological analysis of the electron density in terms of the theory of atoms in molecules (AIM). The calculation results are in agreement with the experimental kinetic data indicating somewhat lower reactivity of triper-oxovanadate compared to the isomeric oxygenyl complexes.

Abstract  Anion exchange membranes for a vanadium redox flow battery (VRB) were prepared by pore-filling on a PE substrate with the copolymerization of vinylbenzyl chloride (VBC) and glycidyl methacrylate (GMA). The ion exchange capacity, water uptake and weight gain ratio were increased with a similar tendency up to 65% of GMA content, indicating that the monomer improved the pore-filling degree and membrane properties. The vanadium ion permeability and open-circuit voltage were also investigated. The permeability of the VG65 membrane was only 1.23 x 10(-7) cm(2) min(-1) compared to 17.9 x 10(-7) cm(2) min(-1) for Nafion 117 and 1.8 x 10(-7) cm(2) min(-1) for AMV. Consequently, a VRB single cell using the prepared membrane showed higher energy efficiency (over 80%) of up to 100 cycles compared to the commercial membranes, Nafion 117 (ca. 58%) and AMV (ca. 70%).

Abstract  Effect of zirconium presence in the silica framework and content and speciation of vanadium surface oxo-complexes on the catalytic behavior of VOx/Zr-SBA-15 catalysts in oxidative dehydrogenation of ethanol was investigated. Experimental results bring evidence of successful incorporation of zirconium into ordered mesoporous silica framework with the preservation of ordered mesoporosity by hydrothermal template base synthesis method. The presence of zirconium in the SBA-15 framework increases reducibility of vanadium species and acidity of the catalysts. It is reflected in higher activity of vanadium species expressed as turn-over frequency (e.g., TOF of 20 h(-1) for 5%VOx/Zr-SBA-15 sample in comparison with TOF of 12 h(-1) for 5%VOx/SBA-15 sample) and also in significant decrease of selectivity to acetaldehyde (65% in comparison with 90% for mentioned samples) followed by increase in selectivity to ethylene (25% in comparison with 5%). This change in distribution of reaction products is related to stronger acidity character of surface OH groups and inhibition effect of formed water vapours on the oxidative dehydrogenation products (acetaldehyde). Catalytic data also reveal that oligomeric/polymeric tetrahedrally coordinated vanadium species exhibit higher activity in ethanol oxidative dehydrogenation than monomeric complexes. In addition, comparison of the catalytic performance of VOx/Zr-SBA-15 catalysts with VOx/SBA-15 catalysts showed that catalytic properties of VOx/Zr-SBA-15 catalysts can be tuned by incorporation of controlled amount of zirconium into silica framework.

Abstract  Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. Understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions is therefore critical to developing conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring within organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250km transect of the central UCRB. The results of this study support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. We found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.

Abstract  A green route is designed to gain a clear idea of growth mechanism of complex VO2 (B) hierarchical microstructures, since this kind of metal oxide has various metastable phases due to their diverse valence states. Three-dimensional (3D) uniform flower-like VO2 (B) hierarchical microstructure has thus been assembled with the interleaving nanoplates, which are about 25 nm in thickness and well-crystallized in structure with {114} planes as the dominant surfaces. Results of the systemic control experiments revealed that formation of the flower-like VO2 (B) results from a fast nucleation-growth process, where ethylene glycol (EG) not only acts as a green solvent and reductive agent, but also plays a key role in self-assembly of the resulted VO2 (B) hierarchical microstructures. Hydroxyl amount on the solvent molecule is crucial in formation and shape control of VO2 (B) hierarchical microstructures. Result of this work would be helpful to understand the growth mechanism of complex three-dimensional hierarchical superstructures of different metal oxides, which is very important to material science and inorganic synthetic chemistry.

Abstract  Utilization of CO 2 as a feedstock for synthesis of chemicals is an alternate and most promising option for CO 2 abatement. In the present study, CO 2 has been utilized as a soft oxidant for oxidative dehydrogenation of ethylbenzene and n-butane to the corresponding olefins. For this, TiO 2?ZrO 2 (TZ) mixed oxide-supported V 2O 5, C eO 2 and V 2O 5-C eO 2 catalysts has been synthesized, characterized and evaluated for the oxidative dehydrogenation reactions. The physicochemical characterization has been achieved by various techniques such as, powder X-ray diffraction, CO 2 and NH3 temperature-preprogrammed desorption, temperature-preprogrammed reduction, X-ray photoelectron spectroscopy and BET surface area methods. XRD analysis of the samples calcined at 550 °C indicates that the impregnated active components are in a highly dispersed state on the support. XP spectra shows the existence of vanadium and cerium in V 4+ and C e4+/C e3+ oxidation states, respectively. Among the various catalysts investigated, V 2O 5?C eO 2/TiO 2?ZrO 2 exhibits a high conversion and product selectivity for the oxidative dehydrogenation of ethyl benzene. On the other hand, a high conversion and selectivity in the oxidative dehydrogenation of n-butane is noted over V 2O 5/SnO 2?Z rO 2 mixed oxide catalyst. The combined acid-base and redox properties of the catalysts play a major role in these reactions. In particular, the characterization studies reveal that mixed oxides show a high specific surface area, superior acid-base properties and better redox characteristics. All these properties enhance the catalytic performance of mixed oxide catalysts.

Abstract  Oxidative dehydrogenation (ODH) of n-butane was investigated over ZrO2, SnO2 and SnO2-ZrO2 mixed oxide supported vanadium oxide catalysts with the aim of utilizing CO2 as the soft oxidant, and to study the effect of mixed oxide support on the ODH activity and C4 olefins selectivity. The acid-base properties, reducibility, surface area and morphology of the SnO2-ZrO2 mixed oxide and its individual component oxide supported vanadium oxide samples were thoroughly studied. The mixed oxide supported vanadia sample exhibited superior acid-base bifunctionality: in particular, more numbers of medium strength acid-base sites were observed. The reduction temperature of the vanadia was observed to decrease in the case of mixed oxide supported vanadia catalysts. The mixed oxide supported vanadia sample exhibited a high conversion and product selectivity than its individual component oxide supported vanadia samples. A significant difference in the catalyst activity was noted in the presence and absence (He) of CO2 feed gas. Among various catalysts evaluated. the VOx/SnO2-ZrO2 catalyst exhibited excellent performance (22.34 and 36.63% conversion of n-butane and selectivity of C4 olefins, respectively), which is attributed to a high specific surface area, superior acid-base bifunctionality and easily reducibility of the dispersed vanadium oxide. (C) 2012 Elsevier B.V. All rights reserved.

Abstract  In this study, nano-crystalline vanadium carbide was synthesized through reduction of V2O5 by carbon and Ca using high energy ball milling and subsequent heat treatment. Vanadium pentoxide, calcium and carbon black were placed in a planetary ball mill and sampled after different milling times. The activated powders were synthesized by microwave heating at temperatures 800 degrees C. XRD and FESEM were used for characterization of synthesized powder. On the basis of obtained results, the synthesized V8C7 crystallites were in the scale of nanometers and the lattice parameter had some deviation from the standard value. Furthermore, investigations showed that at higher milling time, the amorphization degree of V4C3 phase increased, while the degree of crystallite decreased. Crown Copyright (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. All rights reserved.

Abstract  This paper presents the characterization studies conducted by Milwaukee School of Engineering senior undergraduate students in South Africa under the Research Experiences for Undergraduates grant EEC-1460183 sponsored by the National Science Foundation (Principal Investigator Dr. Kumpaty). Robert Mueller and Christopher Reynolds conducted research in summer of 2015 under advisement of Dr. Kumpaty and his South African collaborators, Dr. Esther Akinlabi and Dr. Sisa Pityana. The foreign collaborators' excellent support was pivotal to the success of our U.S. students.

Ti-6Al-4V is a titanium alloy that accounts for about 80% of the titanium market. The Ti-64 alloy contains 6 wt% Aluminum and 4 wt% Vanadium, an almost equal ratio of alpha + beta phases. Through the laser surface modification process known as Laser Meal Deposition, this alloy offers the optimum combination of enhanced properties. This research focuses on the application of adding a combination of molybdenum (Mo) and Ti-64 powders to a Ti-64 substrate surface in order to improve the durability for various biomedical/aerospace applications. Deposition of the powders was completed at the CSIR - National Laser Center, in Pretoria, South Africa. The characterization studies were carried out at the University of Johannesburg. The results of the hardness tests showed that the addition of molybdenum to Ti-64 increased the hardness of the deposited material compared to that of the substrate. This verifies that the addition of Mo to metals can affect the mechanical properties to better suit various applications.

While Robert Mueller studied the effect of laser power on the properties of laser metal deposited Ti-6Al-4V + Mo for wear resistance enhancement, Christopher Reynolds investigated scanning velocity influence on the evolving properties of laser metal deposited Ti-6Al-4V + Mo. The results of this promising research and various options for further investigation are presented. The beneficial value of such a global research enterprise on the budding engineers will be apparent and the paper details the process of the international component of the Research Experiences for Undergraduates.

Abstract  V(0.5)Mo(0.5)Nx/MgO(001) alloys with the B1-NaCI structure are grown by ultra-high-vacuum reactive magnetron sputter deposition in 5 mTorr mixed Ar/N-2 atmospheres at temperatures T-s between 100 and 900 degrees C. Alloy films grown at T-s <= 500 degrees C are polycrystalline with a strong 002 preferred orientation; layers grown at T-s >= 700 degrees C are epitaxial single-crystals. The N/Metal composition ratio x ranges from 1.02 +/- 0.05 with T-s = 100-500 degrees C to 0.94 +/- 0.05 at 700 degrees C to 0.64 +/- 0.05 at T-s = 900 degrees C. N loss at higher growth temperatures leads to a corresponding decrease in the relaxed lattice parameter a(0) from 4.212 A with x = 1.02 to 4.175 angstrom at x = 0.94 to 4.120 angstrom with x = 0.64. V(0.5)Mo(0.5)Nx nanoindentation hardnesses H and elastic moduli E increase with increasing T-s, from 17 +/- 3 and 323 +/- 30 GPa at 100 degrees C to 26 +/- 1 and 370 +/- 10 GPa at 900 degrees C. Both polycrystalline and single-crystal V(0.5)Mo(0.5)Nx films exhibit higher toughnesses than that of the parent binary compound VN. V(0.5)Mo(0.5)Nx films deposited at higher Ts also exhibit enhanced wear resistance. Valence-band x-ray photoelectron spectroscopy analyses reveal an increased volume density of shear-sensitive d-t(2g) d-t(2g) metallic states for V(0.5)Mo(0.5)Nx compared to VN and the density of these orbitals increases with increasing deposition temperature, i.e., with increasing N-vacancy concentration.(C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Abstract  We report the fabrication and properties of high performance and inexpensive composite membranes of sulfonated polyimide (SPI) and sulfonated molybdenum disulfide (s-MoS2) for the vanadium redox flow battery (VRFB) application. Scanning electron microscopy (SEM) images reveal the uniformity of SPI/s-MoS2 membrane. Both EDS and XRD results verify the existence of s-MoS2 in SPI/s-MoS2 membrane and show the interaction between SPI and s-MoS2. The physico-chemical properties of as-prepared SPI/sMoS(2) membrane, including water uptake and ion exchange capacity, etc. are evaluated and compared to those of SPI SPI/MoS2 and Nafion 117 membranes, respectively. The SPI/s-MoS2 membrane possesses increased proton conductivity and reduced vanadium ion permeability than pure SPI membrane, and it has the highest proton selectivity (2.24 x 10(5) S min cm(-3)) among all membranes. The VRFB with SPI/sMoS(2) membrane presents a higher coulombic efficiency (CE) and energy efficiency (EE) compared with Nafion 117 at the current density ranging from 20 to 80 mA cm(-2). The SPI/s-MoS2 membrane shows a longer discharge time (193 h above 0.8 V) than Nafion 117 (72 h). Moreover, the SPlis-MoS2 membrane exhibits stable operation performance up to 500 cycles with no significant decline in CE and EE. All experimental results confirm that the SPI/s-MoS2 membrane is suitable for use in VRFB. (C) 2015 Elsevier B.V. All rights reserved.

Abstract  An efficient catalytic process for the oxidative dehydrogenation of biomass-derived lactic acid by earthabundant MoO3/TiO2 mixed oxide catalysts is presented. A series of MoO3/TiO2 materials with varied MoO3 loadings were prepared and their performance in the aerobic and anaerobic conversion of lactic acid was evaluated. A strong synergistic effect between MoO3 and TiO2 components of the mixed oxide catalyst was observed. Optimum catalysts in terms of activity and pyruvic acid selectivity can be obtained by ensuring a high dispersion of MoOx species on the titania surface. Mo-oxide aggregates catalyze undesired side-reactions. XPS measurements indicate that the redox processes involving supported Mo ions are crucial for the catalytic cycle. A mechanism is proposed, in which lactic acid adsorbs onto basic sites of the titania surface and is dehydrogenated over the Mo=O acid-base pair of a vicinal tetrahedral Mo site. The catalytic cycle closes by hydrolysis of surface pyruvate and water desorption accompanied by the reduction of the Mo center, which is finally oxidized by O-2 to regenerate the initial active site. Under anaerobic conditions, a less efficient catalytic cycle is established involving a bimolecular hydrogen transfer mechanism, selectively yielding propionic and pyruvic acids as the major products. The optimum catalyst is 2 wt% MoO3/TiO2 predominantly containing tetrahedral Mo species. With this catalyst the oxidative conversion of lactic acid at 200 degrees C proceeds with a selectivity of ca. 80% to pyruvic acid. The pyruvic acid productivity is 0.56 g g(-1) h(-1).

Abstract  Focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller gas adsorption methods have been used for the characterisation of physical properties of microporous carbide-derived carbon electrodes, prepared from Mo2C at 600 A degrees C (noted as Mo2C-CDC) before and after electrochemical tests conducted within a very wide two-electrode cell potential region. Cyclic voltammetry, constant current charge/discharge and impedance data have been analysed to establish the electrochemical characteristics of the hybrid devices consisting of the 1 M Na2SO4 and 1 M Rb2SO4 aqueous electrolytes and Mo2C-CDC electrodes within the very wide cell potential region (Delta E a parts per thousand currency signaEuro parts per thousand 2.4 V). The influence of cation chemical composition on the electrochemical characteristics of supercapacitors/electrochemical hybrid devices has been analysed. The complex kinetics behaviour of completed devices (adsorption, blocking adsorption and intercalation of Na+ and Rb+ ions; faradic and mass transfer; gas adsorption; etc.) has been established at Delta E a parts per thousand yenaEuro parts per thousand 1.5 V. At least three different characteristic time constants dependent on the electrolyte cation composition and cell potential applied have been established.

Abstract  Neutral bis(pentalene) metal sandwich compounds have been synthesized for the first row transition metals titanium and iron. In this connection, the complete series of first row transition metal bis(pentalene) metal complexes (C(8)H(6))(2)M (M = Ti, V, Cr, Mn, Fe, Co, Ni) has now been investigated by density functional theory in order to evaluate the effect of the metal electronic requirements on the hapticity of the pentalene ligands. The lowest energy structure for the titanium complex is the 18-electron complex (eta(8)-C(8)H(6))(eta(6)-C(8)H(6))Ti with one octahapto and one hexahapto pentalene ligand rather than the previously suggested 20-electron complex (eta(8)-C(8)H(6))(2)Ti with two octahapto pentalene ligands. The experimental NMR observations on (C(8)H(6))(2)Ti can then be reinterpreted as interchange of octahapto and hexahapto bonding of the pentalene units through a low energy bis(octahapto) (eta(8)-C(8)H(6))(2)Ti transition state. The lowest energy structure for (C(8)H(6))(2)V has two fulvene-like hexahapto pentalene ligands and a local vanadium environment similar to the well-known dibenzenevanadium. The lowest energy structures of the later first row transition metals have two pentahapto pentalene ligands with local metal environments similar to those in the corresponding metallocenes. In the manganese and iron structures of this type, the remaining unpaired electrons on one of the uncomplexed carbon atoms in each eta(5)-C(8)H(6) system form a C-C single bond to couple the two pentalene ligands. This coupling of the two pentalene systems through a C-C single bond is similar to that found experimentally by X-ray crystallography in bis(pentalene) iron, (eta(5)-C(8)H(6))(2)Fe.

Abstract  A method for the simultaneous determination of aluminum (Al), arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), phosphorus (P), lead (Pb), sulfur (S), selenium (Se), vanadium (V), and zinc (Zn) in organic soil amendments using microwaveassisted acid digestion and inductively coupled plasma optical emission spectroscopy (ICP OES) is proposed. Concentrated or diluted acids mixtures (HNO3, HF, HBF4, and H3BO3) combined or not with H2O2 were systematically evaluated in order to achieve the best digestion procedure for masses of around 150 mg of samples. Principal component analysis (PCA) was applied in order to choose the best acid mixture for digestion (3 mL HNO3 + 1 mL HBF4 + 2 mL H2O). The determined concentrations were in accordance with certified values of CRM 029 at the 95% confidence level, according to the Student-t test. This acid mixture was successfully applied for the digestion of four organic soil amendment samples (organic fertilizers, substrates, and soil conditioners) and element determination.

Abstract  Transitional metal carbides have great potential to overcome the shortcomings of high cost and rare sources of precious metal based catalysts. In this paper, we report the catalytic performances of commercial vanadium carbide (VC) and the influences of nitrogen doping on its catalytic performance towards oxygen reduction reactions. Results showed that nitrogen has been doped into the crystal lattice of commercial VC with a slight increase of crystalline size. The half-wave potential of oxygen reduction of the commercial VC and nitrogen doped VC was only 0.06 V and 0.04 V lower than that of Pt/C catalyst, respectively. The stability of VC for catalyzing oxygen reduction could be improved by nitrogen doping. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.