Novel WS2/Fe0.95S1.05 Hierarchical Nanosphere as a Highly Efficient Electrocatalyst for Hydrogen Evolution Reaction

Fe_0.95S_1.05 with high reactivity and stability was incorporated into WS₂ nanosheets via a one-step solvothermal method for the first time. The resulted hybrid catalyst has much higher catalytic activity than WS₂ and Fe_0.95S_1.05 alone, and the optimal WS₂/Fe_0.95S_1.05 hybrid catalyst was found by adjusting the feed ratio. The addition of Fe_0.95S_1.05 was proven to be able to enhance the hydrogen evolution reaction (HER) activity of WS₂, and vice versa. At the same time, it was found that the catalytic effect of the hybrid catalyst was the best when the feed ratio was W : Fe=2 : 1. In other words, we confirmed that there is a synergistic effect between W- and Fe-based sulfide hybrid catalysts, and validated that the reason for the improved HER performance is the strong interaction between the two in the middle sulfur. WS₂/Fe_0.95S_1.05-2 hybrid catalyst leads to enhanced HER activity, which shows a low overpotential of ∼0.172 V at 10 mA cm⁻², low Tafel slope of ∼53.47 mV/decade. This study supplies innovative synthesis of a highly active WS₂/Fe_0.95S_1.05 hybrid catalyst for HER.     

Novel Reactions of Organomolybdenum and Organotungsten Compounds: Additive–Reductive Carbonyl Dimerization,Spontaneous Transformation of Methyl Ligands into μ-Methylene Ligands,and Selective Carbonylmethylenation

Hitherto there was no reaction known that permits transformations of R¹R²-CO → 0.5 R¹R²R³C–CR¹R²R³ in one step. This type of additive–reductive carbonyl dimerization is now possible using alkoxy(alkyl)tungsten(v) complexes with aromatic, heteroaromatic or α,β-unsaturated aldehydes and ketones. When a corresponding phenyl complex was employed in a test experiment, it was revealed that an aliphatic ketone could be used as the substrate in this reaction. A second interesting type of reaction is the transformation of CH₃ ligands into μ-CH₂ ligands, which occurs during the treatment of MeLi or Me₃Al with molybdenum or tungsten chlorides (oxidation states VI and V, for Mo additionally IV) at low temperatures with liberation of CH₄. Here, the question arises as to whether the intermediate involved has a terminal CH₂ ligand (Schrock carbene complex) or a μ-CH₃ ligand (CH₃ bound by a two-electron three-center bond to two metal atoms). Of all the μ-CH₂ complexes obtained, those which were synthesized by the action of MeLi on molybdenum chlorides can be recommended as reagents for carbonylmethylenation of aldehydes and ketones. They display high selectivity, very low basicity, a surprising resistance to protons, they are readily available, can be easily modified and, as regards their selective behavior, they have been investigated more thoroughly than other readily accessible carbonylmethylenation reagents of comparable selectivity. The results of NMR spectroscopic investigations on the structure of the μ-CH₂ complexes, and associated reaction mechanisms are discussed. A survey of carbonylmethylenation reagents, which have been reported in the literature, permits comparisons to be made with carbonylmethylenating molybdenum and tungsten complexes.     

Al2O3／WO3／ZrO2固体强酸催化剂对正丁烷异构化的催化性能

 通过沉淀、回流、浸渍和焙烧等步骤制备了Al2O3／WO3／ZrO2固体强酸催化剂．采用XRD，N2吸附，UV－Vis光谱，NH3－TPD和H2－TPR等技术测定了Al2O3对WO3／ZrO2催化剂的结构、表面酸性、氧化还原性及正丁烷异构化反应性能的影响．结果表明，在WO3／ZrO2中引入适量的Al2O3对其表面酸强度及酸量无显著影响，但可使催化剂中的ZrO2组分以稳定的四方相形式存在，并能有效地抑制催化剂中WO3的聚集长大，从而提高催化剂的稳定性和正丁烷异构化的转化率和选择性．添加铂于Al2O3／WO3／ZrO2中可进一步提高其催化性能．还考察了催化剂的焙烧温度、Al含量、反应温度和反应气氛对正丁烷异构化反应的影响．     

Electrochemical and structural investigations of oxide films anodically formed on ruthenium-plated titanium electrodes in sulfuric acid

The electrochemical characteristics of ruthenium oxides, formed on Ru-plated Ti electrodes in 0.5 M H₂SO₄ by potential cycling with different CV upper potential limits (E _SU), were systematically compared. The repeated potential cycling between 0.2 and 0.75 V activated the formation/reduction of surface Ru oxides with hysteretic behavior. This application of repeated CVs also modified the ability of Ru deposits for hydrogen adsorption/desorption. An irreducible Ru oxide accumulated on the electrode at potentials more positive than ca. 0.95 V, whose capacitive characteristics are applicable for electrochemical supercapacitors. This irreducible oxide was composed of an aggregate consisting of Ru in various oxidation states, bridged oxygen, OH and water in a 3D-like structure with a relatively ordered and compact nature, from the X-ray photoelectron spectroscopic and voltammetric results. The surface reconstruction of the Ru deposits induced by the repeated potential cycling with E _SU≥0.75 V was clearly observed from the SEM photographs. From the X-ray diffraction patterns, all the anodically formed Ru oxides showed an amorphous nature.     

Reactions of a Silylyne Complex with Aldehydes: Formation of W−Si−O−C Four-Membered Metallacycles and Their Metathesis-Like Fragmentation

A tungsten silylyne complex having a W≡Si triple bond reacted with two molecules of aldehydes at room temperature to give W−Si−O−C four-membered metallacycles by [2+2] cycloaddition and subsequent formyl hydrogen transfer from one aldehyde molecule to another. Upon heating to 70 °C, the four-membered metallacycles underwent metathesis-like fragmentation cleanly to afford carbyne complexes and “silanoic esters,” in a manner similar to that of metallacyclobutadiene, an intermediate of alkyne metathesis reactions, and dimerization of the latter products gave 1,3-cyclodisiloxanes. The “silanoic ester” was also trapped by pivalaldehyde to give a [2+2] cycloaddition product in high yield.     

Frustrated Lewis Pair Chemistry Enables N2 Borylation by Formal 1,3-Addition of a B−H Bond in the Coordination Sphere of Tungsten

The first example of a formal 1,3-B−H bond addition across the M−N≡N unit of an end-on dinitrogen complex has been achieved. The use of Piers’ borane HB(C₆F₅)₂ was essential to observe this reactivity and it plays a triple role in this transformation: 1) electrophilic N₂-borylation agent, 2) Lewis acid in a frustrated Lewis pair-type B−H bond activation, and 3) hydride shuttle to the metal center. This chemistry is supported by NMR spectroscopy and solid-state characterization of products and intermediates. The combination of chelate effect and strong σ donation in the diphosphine ligand 1,2-bis(diethylphosphino)ethane was mandatory to avoid phosphine dissociation that otherwise led to complexes where borylation of N₂ occurred without hydride transfer.     

Chloroaqua Complexes [M3S4(H2O)9?xClx](4?x)+ (M = Mo, W; x = 4, 6, 7) and Their Supramolecular Compounds with Cucur[8]uril

Compounds of trigonal cluster chloroaqua complexes with cucurbit[8]uril were synthesized by slowly evaporating HCl solutions of chalcogenides heterometallic cubane cluster complexes of molybdenum and tungsten with cucurbit[8]uril in air; the complexes were characterized by X-ray diffraction analysis: (H₃O)₈[Mo₃S₄(H₂O)_2.5Cl_6.5]₂Cl(PdCl₄)·(C₄₈H₄₈N₃₂O₁₆)· 29H₂O (a = 13.3183(17) Å, b = 13.7104(18) Å, c = 18.225(3) Å; α = 80.263(3)°, β = 77. 958(3)°, γ = 87.149(4)°, V = 3207.4(7) ų, space group P , Z = 1, ρ(calc) = 1.900 g/cm³), (H₃O)₄ [Mo₃S₄(H₂O)₃Cl₆]₂·(C₄₈H₄₈N₃₂O₁₆)₃·68H₂O (a = 21.413(6) Å, c = 49.832(10) Å; γ = 120°, V = 19788(8) ų, space group R , Z = 3, ρ(calc) = 1.695 g/cm³), (H₃O)₆ [Mo₃S₄(H₂O)₃Cl₆]₂Cl₂·(C₄₈H₄₈N₃₂O₁₆)·12H₂O (a = 15.881(2) Å, b = 17.191(2) Å, c = 23.276(4) Å; β = 98.865(15)°, V = 6278.7(15) ų, space group P2₁/c, Z = 2, ρ(calc) = 1.638 g/cm³), [W₃S₄(H₂O)₅Cl₄]₂·(C₄₈H₄₈N₃₂O₁₆)₃·35H₂O (a = 21.038(3) Å; α = 61.20(1)°, V = 6762.0(14) ų, space group R , Z = 1, ρ(calc) = 1.582 g/cm³). The [Mo₃S₄(H₂O)₃Cl₆]²⁻ anion complex was isolated as three geometrical isomers.Original Russian Text Copyright © 2004 by E. V. Chubarova, D. G. Samsonenko, H. G. Platas, F. M. Dolgushin, A. V. Gerasimenko, M. N. Sokolov, Z. A. Starikova, M. Yu. Antipin, and V. P. Fedin__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1049–1058, November–December, 2004.     

Acid-catalyzed attack of the dinitrogen ligand in thecis-(Me2PhP)4Mo(N2)2 andtrans-(Ph2PCH2CH2PPh2W(N2)2 complexes by nitronium and nitrosonium cations with the formation of nitrogen oxides

The interaction of labeled dinitrogen complexescis-(Me₂PhP)₄Mo(¹⁵N₂)₂ andtrans-(dppe)₂W(¹⁵N₂)₂ with non-labeled nitronium and nitrosonium fluoroborates,¹⁴NO₂BF₄ and¹⁴NOBF₄, in sulfolane at room temperature in the presence of H₂SO₄ results in rapid formation of labeled nitrous and nitric oxides (¹⁵N¹⁴NO,¹⁵NO), as well as¹⁵N¹⁴N. The yield of the products depends on the reagent ratio and reaches 10–20 mol. % per mole of a complex under optimum conditions. The mechanism of the reactions found is proposed. It involves the step of protonation of the dinitrogen ligand to form the corresponding hydrazido(2–) derivatives, which are then attacked by nitronium or nitrosonium cations. In accordance with the mechanism proposed, it was established that the hydrazido(2–) complexes, (Me₂PhP)₃Mo(¹⁵N₂H₂)Cl₂ and (dppe)₂W(¹⁵N₂H₂)Cl₂, are capable of forming¹⁵N¹⁴NO,¹⁵NO, and¹⁵N¹⁴N under the action of¹⁴NO₂BF₄ and¹⁴NOBF₄ in the absence of an acid.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 13–13, July, 1995.