Nanostructured catalysts for cathodes of oxygen-hydrogen fuel cells

Bimetallic catalysts platinum-cobalt, platinum-chromium, and platinum-tungsten, deposited onto highly dispersed carbon black from complex cluster-type compounds of corresponding metals with a 1: 1 atomic ratio of metals are developed. The catalysts are characterized by methods of x-ray diffraction analysis and energy dispersive analysis of x-rays. The procedure involving use of a thin-film rotating disk electrode is employed to probe kinetic parameters of the oxygen reduction reaction on the catalysts developed. The investigated binary catalysts exhibit specific electrochemical characteristics that are not inferior and, in some cases, are superior to the characteristics intrinsic to the commercial platinum catalyst E-TEK, when tested in the composition of a gas-diffusion electrode under conditions that are close to real conditions in which cathodes of oxygen-hydrogen fuel cells operate.     

Synthesis,Structure, and Haptotropic Interconversions of Tungsten Cycloheptatrienyl–Acetonitrile–Carbonyl Complexes

Russian Journal of Coordination Chemistry - Tungsten cycloheptatrienyl complexes (η7-C7H7)W(CO)2I (I), [(η3-C7H7)W(CO)2(CH3CN)3]PF6 (II), and [(η7-C7H7)W(CO)2(CH3CN)]PF6 (III) (CIF...     

The Shortened Transition Metal–Tellurium Bonds in Organometallic Clusters

The shortening of partly multiple M–Te (M = Mn, Fe, Co, Cr or W) bonds is observed for two classes of organometallic compounds: (1) formally electron-deficient species with additional donor–acceptor interaction between Te lone pairs and half-occupied d-orbitals of M; (2) formally electron-saturated species having additional dative interaction between M lone pairs and LUMO of Te. These compounds could be prepared by two main methods: (a) interaction of [CpMn(CO)₂PhC(O)⁻]Li⁺ with Te proceeds via formation of intermediate {[CpMn(CO)₂]₂Te}²⁻ which is further transformed into binuclear complex [CpMn(CO)₂]₂Te(CH₂Ph)₂ or into trinuclear ditelluride cluster [CpMn(CO)₂]₃Te₂ on one hand or to mixed-metal monotelluride clusters [CpMn(CO)₂]₂TeM(CO)₅ on another hand. (b) treatment of Fe(CO)₅, CpMn(CO)₂(THF) or Me₄C₄Co(CO)₂I with [PhTeI]₄, PhTeI₃ or PhTeI₂HC = CPhI results in different PhTeI-containing complexes of Fe, Mn or Co. The molecular structures of all new compounds were studied by means of X-ray diffraction analyses and the mechanism of M–Te bond shortening is discussed. Proceeding of the international workshop on transition metal clusters, 3–5 July 2008, Université de Rennes 1, Campus de Beaulieu, Rennes, France.     

Heterometallic heterochalcogenmethylarsenide clusters: Synthesis,molecular structures,and thermolysis

Reactions of the arsinechalcogenide complexes [Fe₃(μ₃-X)(μ₃-AsCH₃)(CO)₉] (X = Se (Ia) or Te (Ib)) with (PPh₃)₂Pt(PhC≡CPh) (transmetalation reaction) and Cp₂Cr₂(SCME₃)₂S (Cp = π-C₅H₅) (photochemical reaction) gave the heterometallic (heterochalcogen)(methylarsine) clusters [(PPh₃)₂Pt(μ₃-X)(μ₃-AsCH₃)Fe₂(CO)₆] (II and III, respectively), as well as Fe₃(μ₃-X)(μ₃-AsCH₃)(CO)₈(C₅H₅)₂Cr₂(μ₃-S)(μ₂-S ^t Bu)₂ (IV and V, respectively). The structures of complexes II, IV, and V were determined by X-ray diffraction analysis. Thermolysis of all the complexes yielded no metal carbides or oxides.     

流体力学半径对估算胶体微球聚集速率常数的影响

胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径(大于几何半径),因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜(SEM)和动态光散射(DLS)来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响.     

Direct borohydride oxidation electrocatalysts based on Ni-Ru/C and Ni-Ru-F/C alloys

A fluorine-containing bimetallic nickel-ruthenium catalyst on highly disperse carbon black is synthesized based on an organometal nickel complex and a ruthenium cluster in the presence of perfluoroenanthic acid. The resulting catalyst is characterized by the XRD and energy-dispersion analyses and laser mass spectrometry. The overall composition of the catalytic system corresponds to Ni₁₂RuF₅. Calculated on the base of XRD data, the particle size is 10.5–12 nm. According to voltammetric data, the specific characteristics of the synthesized catalyst in the reaction of direct oxidation of sodium borohydride at room temperature surpass the characteristics of nickel-ruthenium catalyst described in the literature.     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.