Electrocatalytic synthesis of polyaniline on non-noble metal electrodes

Electrochemical synthesis (ES) of polyaniline (PAn) at the surface covered by an oxide film is realized at a significantly higher voltage than is needed for the formation of a nonoveroxidized polymer. The involvement of catalytic amounts of the salts of transition metals in ES of PAn essentially facilitates the process at Ti, Ta, Pb, Al and stainless steel electrodes. IrCI²⁻₆ anion was found to be an effective catalyst. During ES, IrCI²⁻₆ forms a complex with aniline, where Ir^IY oxidizes aniline to a radical cation. The formation of radical cation is a limiting stage ES PAn. It is realized in a moment in the presence of IrCI²⁻₆, thus providing a significant decrease of the induction period at a potentiostatic synthesis and the lowering of a working potential at a galvanostatic synthesis. It is shown that the composition of the complex includes Ir^III and 2 aniline molecules, which form a paramagnetic dimer inside a coordination sphere. © 1997 John Wiley & Sons, Ltd.     

Nanocast mesoporous mixed metal oxides for catalytic applications

Since the initial discovery of ordered mesoporous silica in early 1990s, considerable innovations were achieved regarding their synthesis, characterization and applications. One of the best outcomes of these intense research efforts is the development of a solid templating method called “nanocasting”, which is based on using mesoporous silica (or carbon) as a rigid template. This solid-to-solid replication method opened the pathway for synthesizing high surface area non-silica mesostructured materials that are challenging to obtain through conventional self-assembly processes which are based on amphiphilic soft structure-directing agents. In particular, the replicated metal oxide mesostructures obtained by this method were found to be highly versatile for a wide range of applications, especially in catalysis, owing to their large specific surface area. Furthermore, the nanocasting method is particularly suited for the synthesis of mixed metal compositions, favored by the possible confinement of mixed precursors in the nanopores of the template. In this account, we discuss some of the recent developments regarding the synthesis of nanocast mixed metal oxides and their perspectives of catalytic applications. It is here the choice of the authors to place emphasis on a few representative examples of compositions (e.g., non-noble metal-based catalysts, perovskites) and catalytic reactions (e.g., hydrogen production, gas-phase oxidation).     

Study of engineering electronic structure modulated non-noble metal oxides for scaled-up alkaline blend seawater splitting

Scaled-up industrial water electrolysis equipment that can be used with abundant seawater is key for affordable hydrogen production.The search for highly stable,dynamic,and economical electrocatalysts could have a significant impact on hydrogen commercialization.Herein,we prepared energy-efficient,scalable,and engineering electronic structure modulated Mn-Ni bimetal oxides(Mn_0.25Ni_0.75O) through simple hydrothermal followed by calcination method.As-optimized Mn_0.25     

Design of supramolecular metal complex catalytic systems for petrochemical and organic synthesis

Specific features of the behavior of the supramolecular metal complex catalysts based on calixarenes, cyclodextrins, and dendrimers in the reactions of hydroformylation, Wacker oxidation, hydroxylation of aromatics, 2-naphthol coupling, and oxidative coupling of styrenes and benzene were studied. The factors affecting the catalytic activity and selectivity are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 766–778, April, 2008.     

Ultrasound-assisted synthesis of nanostructured transition metal oxides

Ultrasound pretreatment of aqueous solutions of cetyltrimethylammonium bromide as a structure- directing agent has been applied to prepare nanostructured mesoporous Mn, Fe, and Ni oxides. After removal of the template by triple extraction with a water–ethanol solution of sodium acetate or ammonium chloride, air-calcined samples of oxide materials prepared in such a way possess surface areas of about 300–450 m²/g and are thermally stable up to 300°C.     

Catalytic removal of nitric oxides from diesel exhaust over supported metal oxides catalysts

Summary A number of supported metal oxide catalysts were prepared and tested for nitrogen oxide removal from diesel engine exhaust. More than 50% of nitrogen oxides were removed using many prepared catalysts in the temperature range of 150^oC-350^oC.     

Ordered mesoporous metal oxides: synthesis and applications

Great progress has been made in the preparation and application of ordered mesoporous metal oxides during the past decade. However, the applications of these novel and interesting materials have not been reviewed comprehensively in the literature. In the current review we first describe different methods for the preparation of ordered mesoporous metal oxides; we then review their applications in energy conversion and storage, catalysis, sensing, adsorption and separation. The correlations between the textural properties of ordered mesoporous metal oxides and their specific performance are highlighted in different examples, including the rate of Li intercalation, sensing, and the magnetic properties. These results demonstrate that the mesoporosity has a direct impact on the properties and potential applications of such materials. Although the scope of the current review is limited to ordered mesoporous metal oxides, we believe that the information may be useful for those working in a number of fields.     

过渡金属氧化物掺杂对铜锰氧化物催化CO氧化性能的影响

以乙酸铜和乙酸锰为铜锰前驱体,以NH₄HCO₃为沉淀剂,相应金属硝酸盐为掺杂剂,采用共沉淀法制备了不同过渡金属氧化物掺杂的铜锰氧化物催化剂.?采用N₂物理吸附、X射线衍射,氢气-程序升温还原和原位红外漫反射光谱等方法对催化剂进行了表征,考察了系列催化剂上CO反应性能.?结果表明,掺杂过渡金属氧化物可以调变催化剂对CO的吸附能力,进而影响催化剂性能.     

Selective catalytic reduction of NO over metal oxides incorporated zeolites

Selective catalytic reduction (SCR) of nitric oxide in an oxygen-rich atmosphere with propylene as a reductant has been investigated over supported La-Co-oxide (mixed metal oxide) catalysts prepared by the modified citrate method. Loading on ZSM-5 support gave greatly enhanced activity in the reduction of NO at relatively low temperatures. This SCR activity could be ascribed to incorporation of the mixed metal oxide into ZSM-5 as an amorphous perovskite phase via preparation.     

Method to affect catalytic properties of low-temperature transition metal oxides

A method to affect the catalytic properties of low-temperature oxide catalysts by their synthesis through hydroxide compounds of the required composition and structure is suggested.

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水滑石衍生的复合氧化物催化氧化挥发性有机气体的研究进展（英文）

挥发性有机化合物(VOCs)是大气颗粒污染物(PM_2.5)和臭氧污染的主要前体物,来源于工业活动(如溶剂使用过程)、汽车尾气以及植物排放等,具有毒性,对人类和自然生命产生危害.催化氧化技术是在催化剂表面,在较低的操作温度(200-450℃)下,将VOCs非均相催化氧化成CO₂和H₂O,是一种最为有效的分解VOCs的方法,具有副产物少,能耗低的优点.VOCs分解用催化剂主要分为贵金属和金属氧化物两大类.贵金属催化剂活性高,但价格昂贵.因此科研工作者一直在诸多方面调控过渡金属氧化物,例如制备方法、组分协同、结构缺陷等,期望获得高活性、低成本的催化剂.水滑石(LDHs)是一种层状双金属氢氧化物,由带正电荷的金属氢氧化物层板和层间阴离子组成,可以表示为[M_1-x²⁺M_x³⁺(OH)₂](A^n-)_x/n·mH₂O.鉴于LDHs特有的结构特点,层板元素可调、比...     

General routes to porous metal oxides via inorganic and organic templates

The generation of porous metal oxides by removal of template molecules from inorganic polymers formed by sol-gel type hydrolysis and condensation of metal alkoxides is described. The template molecules include organic polymers, copper (II) ions in hybrid copper oxide/silica sols and copper (II) bis(hexafluorocetylacetonate) (hfac). Neutron scattering experiments on the system in which polyacrylic acid (Mw=2,000 Daltons) is used as an organic template to generate microporous tin oxide show that removal of the template generates skeletal voids. In a second series of experiments, mixed copper/silicon oxide xerogels were prepared by hydrolysis of mixtures of Si(OEt)₄ and Cu(OCH₂CH(CH₃)N(CH₃)H)₂ in the ratios of Si:Cu=2:1, 4:1, 9:1. Selective removal (etching) of the copper component generates porous silica. Neutron scattering data and BET surface area measurements are consistent with the creation of pores with molecular dimensions (micropores, 10 Å or less). In the third strategy, Si(OEt)₄ is hydrolyzed in the presence of Cu(hfac)₂, a volatile, inert inorganic template, in a 4 to 1 molar ratio. Removal of the template from the xerogel at 100°C in vacuo affords microporous silica.     

Study on non-noble metal catalysts for automotive emission control

Cordierite honeycomb catalysts supported on rare earth (RE)-transition metal oxides, used for removing simultaneously three major pollutants, carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxides (NO_x), in automotive emission have been investigated. The results indicate that the catalyst has improved three-way performance (TWP).     

General synthesis of mesoporous spheres of metal oxides and phosphates

Monodisperse and high-surface-area mesoporous inorganic spheres of various compositions including metal oxides, mixed oxides, and metal phosphates are prepared by templating mesoporous carbon spheres which are replicated from spherical mesoporous silica. Due to the rigid and thermally stable framework of carbon template, the crystalline phases of the obtained metal oxide spheres can be readily tailored by controlling crystalline temperatures. Moreover, the sphere morphologies can be changed from solid structure to hollow structure in some cases by changing the polarity of the precursor, due to the hydrophobic nature of carbon template.     

Nonequilibrium plasma-chemical synthesis of nanosized particles of metal oxides

The results of investigation into the synthesis conditions and basic characteristics of nanoparticles of titanium dioxide and the mixed oxide (TiO₂)_x(SiO₂)_1?x from a gaseous mixture of oxygen, hydrogen, and titanium tetrachloride (or a mixture of titanium and silicon tetrachlorides) are reported. The synthesis was initiated by a pulsed electron beam and was a chain process in character. The geometric dimensions of oxide particles were measured and their X-ray diffraction, X-ray fluorescence, and IR spectrometric studies were performed. It was shown that the nonequilibrium character of the synthesis process induced by a pulsed electron beam allowed the temperature threshold for the formation of the crystalline structure of particles to be lowered.     

Facile synthesis and catalytic property of porous tin dioxide nanostructures

Porous tin dioxide (SnO(2)) nanostructures consisting of nanoplates are prepared through thermal decomposition of the mixed solution composed of dibutyltin dilaurate and acetic acid. The aggregations of the nanoplates give rise to large macropores with the size of about 100-300 nm. These nanoplates have a wormhole-like porous structure with the size of about 4 nm and possess high surface area. X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, infrared spectroscopy, and nitrogen sorption have been employed to characterize the obtained porous structures. It is found that the obtained nanostructures exhibit excellent catalytic activity toward methanol decomposition. Such porous structures with high surface area have promising industrial applications as catalysts.     

Container effect in nanocasting synthesis of mesoporous metal oxides

We report a general reaction container effect in the nanocasting synthesis of mesoporous metal oxides. The size and shape of the container body in conjunction with simply modifying the container opening accessibility can be used to control the escape rate of water and other gas-phase byproducts in the calcination process, and subsequently affect the nanocrystal growth of the materials inside the mesopore space of the template. In this way, the particle size, mesostructure ordering, and crystallinity of the final product can be systemically controlled. The container effect also explain some of the problems with reproducibility in previously reported results.     

Vanadium-titanium oxides: Sol-gel synthesis and catalytic properties in chlorobenzene oxidation

Vanadium-titanium mixed oxides with V/Ti = 0.025, 0.050, and 0.100 have been synthesized by sol-gel processing. The anatase-rutile transition temperature decreases from 750 to 600°C as the vanadium content of the TiO₂ phase is increased. The most important texture parameters and the photoelectron and IR spectra of the oxides are reported. The oxides exhibit high catalytic activity in chlorobenzene oxidation, which is due to their specific electronic and crystal structures.     

Stereospecific synthesis and catalytic activity of L-histidylidene metal complexes

We report on the synthesis, metal coordination, and catalytic impact of histidylidene, a histidine-derived N-heterocyclic carbene (NHC) ligand. The histidinium salt 3, comprising methyl substituents at both heterocyclic nitrogens and protected at the C- and N-terminus of the amino acid, was rhodated and iridated by a transmetallation protocol using Ag(2)O. Ambient temperature and short reaction times were pivotal for full retention of configuration at the α-carbon. The stereospecificity of the reaction was conveniently probed by (31)P NMR spectroscopy after transmetallation with rhodium(I) and coordination of enantiopure (S)-Ph-binepine. The histidylidene rhodium complexes are highly efficient catalysts for the mild hydrosilylation of ketones. For the cationic complexes [Rh(cod)(histidylidene)(phosphine)](+), lowering the temperature shifted the rate-limiting step of the catalytic reaction to an earlier stage that is not enantioselective. Hence the asymmetric induction-which is governed by the chiral phosphine-did not improve at low temperature.