Comparative analysis of the composition, structure, and catalytic activity of the NiO-CuO-TiO2 on Titanium and NiO-CuO-Al2O3 on aluminum composites

The catalytically active oxide structures based on Al and Ti prepared by plasma-electrolytic oxidation (PEO) and additionally modified by impregnation with an aqueous solution of nickel and copper nitrates followed by annealing were studied. The oxide film-metal composites were studied using X-ray diffraction and X-ray spectroscopic analysis, X-ray electron spectroscopy, and electron microscopy. The catalytic activity of the composites in the reaction of CO oxidation was studied. In spite of differences in the elemental composition and morphology, the initial oxide layers on Al and Ti were comparable in terms of activity. Microgranules of size ～ 1 µm and formations from tens to hundreds of nanometers in size were detected on the surface of PEO layers. The modified layers contained crystalline CuO, NiO, and Al₂O₃ or TiO₂ phases. The surface layers of the modified structures about 3 nm in thickness on AMg5 aluminum alloy and VT1-0 titanium had the same elemental composition but exhibited different activity in the reaction of CO oxidation to CO₂.     

Mn3O4 nanoplates and nanoparticles: Synthesis, characterization, electrochemical and catalytic properties

Mn₃O₄ hexagonal nanoplates and nanoparticles were synthesized via a solvent-assisted hydrothermal oxidation process at low temperature and a solvothermal oxidation method, respectively. The synthesized product was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), electron diffraction (ED), Fourier transform infrared (FT-IR) spectroscopy. Their capability of catalytic oxidation of formaldehyde to formic acid at room temperature and atmospheric pressure and electrochemical properties by cyclic voltammogram (CV) were compared. The results showed that Mn₃O₄ hexagonal nanoplate is a better catalyst, and the hexagonal nanoplates and nanoparticles modified electrodes blended with carbon black have a higher specific capacitance.     

CTAB assisted hydrothermal synthesis, controlled conversion and CO oxidation properties of CeO2 nanoplates, nanotubes, and nanorods

In this work, CeO₂ nanoplates were synthesized by a hydrothermal reaction assisted by hexadecyltrimethylammonium bromide (CTAB) at 100-160 °C. The size of nanoplates was around 40 nm. Further experiment showed that the controlled conversion of nanoplates into nanotubes, and nanorods can be realized by changing the reaction time, temperature, and CTAB/Ce³⁺ ratio value. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption measurements were employed to characterize the samples. The CO oxidation properties of nanorods, nanoplates, and nanotubes were investigated. An enhanced catalytic activity has been found for CO oxidation by using CeO₂ nanoplates as compared with CeO₂ nanotubes and nanorods, and the crystal surfaces (100) of CeO₂ nanoplates were considered to play an important role in determining their catalytic oxidation properties.     

Preparation,properties, and catalytic activity of platinum-modified plasma electrolytic oxide structures on aluminum

Catalytically active Pt-containing oxide composites on aluminum have been prepared by plasma electrolytic oxidation (PEO) and by additional modification of the resulting coating by impregnation with an aqueous solution of chloroplatinic acid followed by calcination. The oxide film/metal composites have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy. The modified films contain the γ-Al₂O₃ and Pt crystalline phases. Platinum in the surface and subsurface layers is in the Pt⁰ state. There are platinum-rich areas on the surface of the PEO films. A higher catalytic activity in CO oxidation into CO₂ is shown by the samples whose oxide film contains nickel and copper along with platinum.     

钙钛矿型氧化物负载纳米金属催化剂结构的动态调变及其催化氧化CO反应性能

研究了钛酸钡和钛酸钙担载的Ag和Pt纳米催化剂的表面结构随氧化-还原处理过程的动态变化及其对CO完全氧化反应性能的影响.发现氧化物担载的Ag催化剂在氧化处理后其催化活性较还原处理的高; X射线衍射(XRD)和X射线光电子能谱(XPS)表征结果表明,氧化处理能够提高载体表面Ag颗粒的分散度,而还原处理导致Ag颗粒的聚集,从而降低了催化氧化CO反应的活性.氧化-还原处理改变了担载Ag纳米粒子的尺寸并影响其CO氧化反应活性.与此相反,氧化物担载的Pt催化剂在还原处理后所表现出的CO氧化反应活性较氧化处理的高; 对比研究发现,氧化和还原处理后Pt纳米粒子的尺寸基本相同,但是氧化处理的样品中Pt表面物种以氧化态为主,而还原处理后Pt表面物种主要为金属态.Pt纳米粒子表面化学状态随氧化-还原处理的调变是导致表面催化活性差异的主要原因.     

Low-Temperature Oxidation of Carbon Monoxide: The Synthesis and Properties of a Catalyst Based on Titanium Dioxide,Nanodiamond, and Palladium for CO Oxidation

A catalyst based on TiO₂ and nanodiamond with a 10 wt % palladium content of the catalyst was synthesized. The effect of the nanodiamond content on the catalytic properties in a reaction of CO oxidation at room temperature and low concentrations of CO (<100 mg/m³) was studied. It was established that, at a nanodiamond content of the catalyst from 7 to 9 wt % and a palladium content of 10 wt %, the rate of CO oxidation reached a maximum, and it was higher by a factor of 2.5 than the rate of CO oxidation on a catalyst based on pure TiO₂, which included palladium clusters. With the use of transmission electron microscopy, XRD X-ray diffractometry, and X-ray photoelectron spectroscopy, it was found that the clusters of palladium covered with palladium oxide with an average cluster size of 4 nm were formed on the surface of the TiO₂ carrier. It was assumed that the catalyst synthesized is promising for applications in catalytic and photocatalytic air-cleaning systems.     

Crystal structure,electrochemical, and antibacterial activity of the sodium complex formed by o-vanillin salicylhydrazone

The mononuclear sodium(I) complex [NaL(HL)] (1) [where HL is (OH)C₆H₄–CO–HN–N=CC₆H₃(OMe)(OH) synthesized by condensation of o-vanillin and salicyloylhydrazine] has been prepared and characterized by IR, elemental analysis, single crystal X-ray diffraction, and cyclic voltammetry. Single crystal X-ray diffraction analysis reveals that NaL(HL) is a neutral complex. Each six-coordinate Na(I) in the unit is linked through O bridges forming a ladder-like arrangement of the 1-D Na(I) double chain. The oxidation–reduction processes have been determined in CH₃CN by cyclic voltammetry. The complex displayed two quasi-reversible reduction couples and one oxidation response between +1.0 and ?0.6 V. The trend in the half wave potentials reflects the electronic nature of the hydrazone ligand. The antibacterial activity results show that the complex possesses strong inhibition activity against Staphyloccus aureus and Bacillus subtilis.     

Synthesis,structure and catalytic properties of Pdii-based bimetallic complexes with ferrocenecarboxylic acid

Novel highly soluble palladium-based complexes with ferrocenecarboxylic acid of general formula [Pd(lut)₂(FcCOO)₂] (lut is 2,6-or 3,4-lutidines) were synthesized and structurally characterized by single-crystal X-ray diffraction. The catalytic oxidation of 1,2-diphenyl-acetylene with these complexes gave dibenzo[a,e]pentalene derivative along with other products.     

Selective and solventless oxidation of organic sulfides and alcohols using new supported molybdenum (VI) complex in microwave and conventional methods

A new dioxo-molybdenum (VI) complex supported on functionalized Merrifield resin ( MR-Mo ) has been synthesized and characterized by elemental, scanning electron mcroscopy, energy-dispersive X-ray analysis, TGA, Brunauer–Emmett–Teller method, powder-X-ray diffraction, Fourier transform infrared, X-ray photoelectron spectroscopy and DRS–UV–vis analysis. The virgin Merrifield resin ( MR ) was functionalized by carbonylation followed by Schiff base formation with ethanolamine ( MR-SB ). Experimental data showed that the Schiff base coordinated with the MoO₂²⁺ moiety via O- and N-atoms. The catalytic activity of MR-Mo was explored under solventless conditions toward the oxidation of organic sulfides and alcohols using 30% aqueous H₂O₂ as oxidant. The oxidation reactions were conducted under microwave and conventional methods. The microwave-assisted oxidation reactions were found to be many times faster than the conventional methods. The oxidation reactions were selective and formed sulfoxides or aldehydes as the sole product with superior TOF values among the molybdenum (VI)-based complexes. Besides these, the MR-Mo was purely heterogeneous in nature and can be recycled for at least five reaction cycles without the loss of catalytic efficiency and product selectivity.     

Mono and dinuclear copper(II) naproxenato complexes containing 3-picoline and 4-picoline: synthesis,structure, properties,catechol oxidase,and antimicrobial activities

Mononuclear and dinuclear copper(II) complexes [Cu₂(μ-nap)₄(3-pic)₂] (1) and [Cu(nap)₂(H₂O)(4-pic)₂] (2) have been synthesized in the presence of 3-picoline and 4-picoline. Two complexes were characterized by FT-IR, UV–vis spectroscopic methods and their thermal stabilities were determined by TG/DTA/DTG techniques. The crystal structures of 1 and 2 were established by X-ray analysis. X-ray structure analysis has shown that copper(II) has a distorted square-pyramidal geometry. Naproxenate is a bridging ligand in 1 and monodentate in 2. Two complexes have shown catalytic activity on oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone exhibiting saturation kinetics at high substrate concentrations. The complexes were also screened for antimicrobial activity against pathogenic bacteria and fungi. The complexes exhibited antimicrobial activity against Entrococcus faecalis and Candida albicans.     

Isolation,Characterisation and Oxidation of Isomeric Ferrelactone Complexes.

Irradiation of 1,2-epoxy-l-vinylcyclopentane (1) in the presence of Fe(CO)₅ leads to the formation of isomeric $\text{syn}$-and $\text{anti}$- ferrelactones (2) and (3). The structures of these complexes were determined by X-ray crystallographic methods and on oxidation gave different ratios of β- and δ-lactones.     

X-ray absorption fine structure study of amorphous metal oxide thin films prepared by photochemical metalorganic deposition

The oxidation state and local geometry of the metal centers in amorphous thin films of Fe₂O₃ (Fe³⁺ oxidation state), CoFe₂O₄ (Co²⁺/Fe³⁺ oxidation states), and Cr₂O₃ (Cr³⁺ oxidation state) are determined using K edge X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The metal oxide thin films were prepared by the solid-state photochemical decomposition of the relevant metal 2-ethylhexanoates, spin cast as thin films. No peaks are observed in the X-ray diffraction patterns, indicating the metal oxides are X-ray amorphous. The oxidation state of the metals is determined from the edge position of the K absorption edges, and in the case of iron-containing samples, an analysis of the pre-edge peaks. In all cases, the EXAFS analysis indicates the first coordination shell consists of oxygen atoms in an octahedral geometry, with a second shell consisting of metals. No higher shells are observed beyond 3.5 Å for all samples, indicating the metal oxides are truly amorphous, consistent with X-ray diffraction results.     

Novel Co5 Cluster Based Triazole Bridged Cobalt-Fluorophosphate: Synthesis,Structure, Magnetic and Heterogeneous Catalytic Epoxidation Studies

A novel triazole bridged cobalt fluorophosphate coordination polymer with the formula {Co₅(1,2,4-triazole)₂(OH)₂(PO₃F)₄}_n has been synthesized. Single crystal X-ray studies reveal that the compound comprises of Co₅ clusters which ultimately build the whole framework, here all cobalt centers are in octahedral geometry established from continuous shape analysis. All the cobalt centers are in Co(II) oxidation state and the results are supported by the bond valence sum (BVS) calculation. The sample has been characterized by single crystal X-ray, powder X-ray, FTIR and TGA analysis. The compound was tested for olefin catalysis performance and magnetism. Magnetization measurements reveal overall antiferromagnetic interactions among the Co(II) ions. The compound is very active in the catalytic transformation of olefins to their corresponding epoxides. Catalytic epoxidation studies reveal that cyclohexene and styrene can be converted up to 97 % with almost 65 % selectivity of products with higher TON numbers.     

M/Al2O3-CeO2（M=Pt-Ru，Ru，Pt）催化剂在甲胺催化湿式氧化中的活性与选择性

采用浸渍法制备了M/Al₂O₃-CeO₂（M=Pt-Ru,Ru,Pt）催化剂,并将其用于甲胺的催化湿式氧化反应（CWAO）.结果表明,Pt-Ru/Al₂O₃-CeO₂具有最佳活性和选择性.运用程序升温还原、X射线光电子能谱、X射线衍射、透射电子显微镜、N₂吸附和CO化学吸附等技术对催化剂的物化性质进行了表征.Pt组分的引入可有效提高双金属催化剂活性组分的分散度,从而明显提高了其催化性能.升降温过程中总有机碳（TOC）转化率与N₂选择性迟滞效应表明,甲胺CWAO遵循化学吸附-脱附机理.     

氧化钛/氧化石墨纳米复合材料的制备、表征及性能

采用四氯化钛(TiCl₄)和氧化石墨为主要原料, 通过原位复合的方法制备了氧化钛/氧化石墨(TiO₂/GO)纳米复合材料. 采用傅里叶变换红外(FTIR)光谱仪、X射线衍射(XRD)仪、热重-差热分析(TG-DTA)仪、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)等手段研究了TiO₂/GO纳米复合材料的结构和性能. 结果表明, 石墨在氧化过程中结构层键合大量含氧官能团, 部分含氧官能团进一步与纳米TiO₂以化学键结合; 复合后氧化石墨原有衍射峰消失. 将TiO₂/GO添加到水性聚氨酯(WPU)中, 制备了TiO₂/GO-WPU复合涂膜. 紫外吸收光谱表明, 随着氧化石墨含量的增加, 复合涂膜的紫外吸收能力增强, 当GO含量达到一定数值时, 涂膜的紫外吸收最强, 随着GO含量继续增加吸收又呈下降趋势, 存在一较优浓度值. TiO₂/GO的添加显著提高了聚氨酯涂层的抗紫外线性能, 耐磨损性能和热稳定性能.     

Spontaneous Bi-modification of polycrystalline Pt electrode: fabrication, characterization, and performance in formic acid electrooxidation

Spontaneous modification of polycrystalline Pt by irreversibly adsorbed bismuth was performed in BiCl₃ solution in concentrated hydrochloric acid under open-circuit conditions. After spontaneous modification, followed by extensive rinsing with water and drying, the surface was characterized using X-ray photoelectron spectroscopy and electrochemistry. Bi-oxy(chloride), oxide species, and metallic Bi were found at a submonolayer coverage on the Pt surface after spontaneous modification. The electrochemical response of Bi-modified polycrystalline Pt electrode in sulfuric acid solution exhibits a complex multi-peak feature, which is resulting in about constant redox charge (Bi species coverage) in the potential region from 0 to 0.9 V (vs. a standard hydrogen electrode). The spontaneously Bi-modified Pt catalyst in model studies exhibits a superior activity towards formic acid oxidation at fuel cell anode relevant potentials. The catalytic effect of bismuth oxy-species is explained in terms of both inhibition of CO_ad formation and oxidation of CO_ad in reaction with Bi-oxy-species.     

A new dirhodium tetraacetate carbenoid: Synthesis, crystal structure and catalytic application

A new dirhodium tetraacetate II involving 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene I was synthesized and characterized by general spectroscopic tools in the solution state as well as single X-ray crystallographic analysis in the solid state. The catalytic activity of dirhodium tetraacetate carbenoid II was tested for the allylic oxidation, and the improved reactivity to the allylic oxidation was observed compared to that of Rh₂(OAc)₄. The different electrochemical properties of dirhodium tetraacetate carbenoid II and Rh₂(OAc)₄ were compared via cyclic voltammetry.     

Synthesis,structures, electrochemistry and catalytic activities of copper(II) and palladium(II) complexes with asymmetric tetraazacycloannulenes

Copper(II) and palladium(II) complexes with 15-membered asymmetric 5,9-dihydro-2,4,10,12-tetramethyl-1,5,9,13-monobenzotetraazacyclo[15]tetradecine have been synthesized and characterized. The electrochemical behaviors of the complexes showed a reduction and two one-electron irreversible oxidation waves in given potential ranges due to the metal ion and macrocycle ring, respectively. The electrocatalytic reduction of dioxygen on glassy carbon electrodes electropolymerized by such 15-membered and 14-membered tetraazaannulene complexes occurred at 160–280 mV (versus SCE), less negative than on the bared one at pH 7.0. The catalytic activities of the copper(II) complexes in the oxidation of p-Xstyrene (X = OCH₃, CH₃, H, F, Cl) were higher than those of the palladium(II) ones. The structures of the 15-membered copper(II) and palladium(II) complexes were determined using the X-ray diffraction method.     

Coordination of reduced Schiff base anion to Pd(II): Synthesis,characterization, DFT calculation and catecholase activity

The article reports the synthesis and characterization of a new palladium(II) complex of type [(L_NNN¹⁻)PdCl] (1) where L_NNN¹⁻ is a mono anionic Schiff's base having a imine bond in reduced state. The L_NNN¹⁻ is generated from a tridentate NNN donor ligand (L_NNN) through in-situ reduction using sodium borohydride, where L_NNN is [(E)-N-(phenyl(pyridine-2-yl)methylene)quinoline-8-amine)]. 1 is characterized by the single crystal X-ray diffraction study, IR, mass and UV–Vis spectroscopy. The X-ray bond parameter authenticates the imine bond of the coordinated Schiff's base anion is in reduced state. 1 exhibits catalytic activity towards the oxidation of 3,5-ditertiarybutyl catechol(3,5-DTBC) with turnover number (K_cat) ​= ​135.6 h^-1. The catalytic oxidation of 3,5-DTBC is authenticated by the UV–Vis, mass and EPR spectroscopy. An isotropic EPR signal with g ​= ​2.011 of a solution containing 1 and 3,5-DTBC authenticating the generation of organic radical during the oxidation process. Cyclic voltammogram of 1 displays an irreversible anodic wave at +0.22 ​V may be due to the oxidation of N⁻ to N^•−. The atomic spin density of 1⁺ obtained from DFT calculation is also supporting the N-centre oxidation process.     

Microstructure, surface and electrochemical studies of electroless Cr–P coatings tailored for the methanol oxidative fuel cell

Cr–P is a new material of great importance as a decorative coating with nickel in automobile industries. Electroless plating of Cr–P alloy has been carried out using a suitable plating bath solution and working conditions. The deposit is characterized by X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray diffraction, X-ray photoelectron spectroscopy and polarization techniques. New phases appear on heat treatment of the coating. The composition (Cr/P) of the coating and the oxidation states of alloying elements vary from the surface to the bulk of the material. The coatings acted as a novel electrode material with good electrocatalytic activity (low overvoltage) and good corrosion resistance for anodic oxidation of methanol in H₂SO₄ at normal working temperature. The good corrosion resistance of the Cr–P film is accounted for by the existence of a double oxyhydroxide passive film on the surface. The electrocatalytic activity of Cr–P is very high when compared with chromium alone.