Optimization of platinum dispersion in Pt–PEM electrodes: application to the electrooxidation of ethanol

Nafion® can be used as a solid polymer electrolyte in a PEM fuel cell. Direct platinization of the membrane was realized by chemical reduction of a platinum compound. The platinization procedure was modified to enhance the roughness factor and thus to improve the electrocatalytic activity towards ethanol electrooxidation. The Pt–PEM electrodes were characterized by TEM, atomic absorption analysis, cyclic voltammetry and their polarization curves for ethanol electrooxidation.     

Decolorization of Methyl Orange Dye at IrO2‐SnO2‐Sb2O5 Coated Titanium Anodes

A film of iridium and tin dioxides doped with antimony oxide (IrO₂‐SnO₂‐Sb₂O₅) was deposited onto Ti mesh and plate substrates by the Pechini method. The electrode surface morphology and composition were characterized by SEM‐EDS. The ternary oxide coating was used for the anodic oxidation of methyl orange (MO) azo dye. Linear sweep voltammetry was used to identify the electrode potentials that favour MO degradation. Batch electrolyses were then carried out at a constant electrode potential of 1.5, 1.75 and 2.0 V vs. SHE using either a three‐electrode batch cell or a flow reactor. The dye solutions were totally decolorized via reactive oxygen species, such as ^?OH, H₂O₂ and O₃ formed in situ from water oxidation at the Ti/IrO₂‐SnO₂‐Sb₂O₅ surface.     

PAHs in Sediments Contaminated by the Haven Oil Spill. (Genoese Bay)

Sediment samples were collected 40 months after the wreckage of the HAVEN off shore Arenzano, facing the Genoese coast, at 300 to 500 m depth, (wreckage zone) and analysed by UV fluorescence spectroscopy and CG/MS. PAHs as alkylated naphtalene, fluorene, phenanthrene, dibenzothiophene series have been studied. Analytical results reveal – 1° – a great alteration of alkylated homologues compared to parent compounds - 2° - the appearance of anthracene (absent in the original crude oil) in samples – 3° – a relative increase of high molecular weight PAHs (4–5 rings and more) as benzo(ghi)perylene and indeno(cd)pyrene. These changes result from the partial burning of the contaminant oil. A beginning of biodegradation is observed for alkylated phenanthrenes.     

Effect of filler dispersion degree on the Joule heating stimulated recovery behaviour of nanocomposites

Composites based on highly branched ethylene-1-octene copolymer (EOC) and carbon black (CB) with different dispersion degree of CB were prepared. The method of the online measured electrical conductance/resistance was used to monitor the change of the electrical conductance/resistance of the composites during the preparation processes, i.e. mixing and cross-linking. It was found that the kinetics of thermally stimulated shape-memory recovery of CB filled EOC is strongly influenced by the filler dispersion degree, which actually affects the heat transfer in the composites. Using a special arrangement of experiments the Joule heating stimulated shape-memory behaviour was quantified. CB dispersion degree and related electrical resistivity determine the extent of the Joule heating stimulated shape-memory behaviour. Composite collected at the maximum in the online measured conductance–time characteristics showed the best shape-memory effect owing to the highest electrical conductivity in the solid state. The CB filled EOC showed a negative thermal coefficient of resistivity (NTC) effect, which accelerates the temperature increase and shape-memory recovery of the composites when applying a voltage.     

Synthesis, characterization and electrochemical properties of 4.8 V LiNi0.5Mn1.5O4 cathode material in lithium-ion batteries

In this work the synthesis of a nickel doped cubic manganese spinel has been studied for application as cathode material in secondary lithium batteries. Six different experimental approaches have been tested in order to carry out a screening of the various possible synthetic routes. The used synthetic strategies were wet chemistry (WC), solid state (SS), combustion synthesis (CS), cellulose-based sol-gel synthesis (SG-C), ascorbic acid-based sol-gel synthesis (SG-AA) and resorcinol/formaldehyde-based sol-gel synthesis (SG-RF). The goal of our study is to obtain insights about how the synthesis conditions can be modified in order to achieve a material with improved electrochemical performances in such devices, especially in high current operating regimes. The synthesized materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), atomic absorption, inductively coupled plasma (ICP-MS) atomic emission spectroscopy, surface area measurements and tested as high voltage cathodes in Li-ion electrochemical devices.     

核探针技术的初步应用

使用新建成的核探针开展了阿米巴细胞中微量元素锌的含量及其分布的观察;锰矿物中微米级矿粒和矿物相的分析;深海锰结核内微米级层状结构的分析;反球化元素对球墨铸铁的影响以及微量元素的偏析造成不锈钢零件局域性断裂的研究。     

Catalytic wall reactor: Catalytic coatings of stainless steel by VOx/TiO2 and Co/SiO2 catalysts

Catalytic wall (structured) reactors and structured supports are suitable to study the catalytic properties of nanosized materials. The coating of metallic (aluminum and stainless steel) plates by thin layers of active phase is presented in two cases, VO_x/TiO₂ and Co/SiO₂, catalysts used in the oxidative dehydrogenation (ODH) of propane and in Fischer–Tropsch synthesis (FTS) of clean fuels, respectively. The preparation of coated plates and their characterisation by various methods of physicochemical analysis are described. Both chemical and physical methods were used for coating. VO_x/TiO₂ layers were obtained by grafting of Ti (on Al or stainless-steel plates) and V (on TiO₂) alkoxides and use of sol–gel media or suspension. A silica primer was deposited (on stainless-steel plate) by plasma-assisted chemical vapour deposition (PACVD) onto which Co oxide and silica were coprecipitated from sol–gel. The catalytic experiments in the respective reactions were carried out in special plate reactors and compared with those of catalytic powders. The study shows that the coating of a metallic substrate by a catalyst is not straightforward and requires specific studies dealing with both chemistry (chemical affinity between substrate and catalytic layers) and catalytic engineering (catalytic performance in taylor-made reactors).     

Design and characterization of a one‐compartment scale‐down system for simulating dissolved oxygen tension gradients

BACKGROUND: A laboratory scale one‐compartment scale‐down system (1‐CSDS), used to generate dissolved oxygen tension (DOT) gradients was designed and characterized. The system consists of a 1.5‐L stirred‐tank bioreactor coupled to an automatic DOT controller that changes the oxygen partial pressure in the inlet gas through a feedback proportional–integral–derivative algorithm, while maintaining the hydrodynamic conditions constant. Oscillatory control of DOT was achieved by employing time‐dependent square wave or sinusoidal setpoints. RESULTS: The 1‐CSDS can be modeled as a first‐order dynamic system, but showing a permanent lag between the system response and the setpoint. The 1‐CSDS had a faster response rate for generating oscillating DOT when a square wave setpoint was used rather than a sinusoidal setpoint. The 1‐CSDS generated symmetric DOT oscillations at periods above of 100 s. CONCLUSION: The 1‐CSDS is suited to investigate the responses of microorganisms and cells, of biotechnological importance, to oscillatory DOT conditions. It was found that the response of the 1‐CSDS was limited by the k_La. Copyright © 2010 Society of Chemical Industry