IN-SITU UV-VISIBLE SPECTROELECTROCHEMICAL AND CIRCULAR DICHROIC ELECTROCHEMICAL STUDY OF BILIRUBIN AND BILIRUBIN PLUS HUMAN SERUM-ALBUMIN COMPLEX

The electro-oxidation of bilirubin (BR) in aqueous solution was investigated by cyclic voltammetry and in-situ thin-layer spectroelectrochemical techniques, It was found that both oxidation processes of BR are two electron transfer reactions. A mechanism

LIQUID-CHROMATOGRAPHY WITH ELECTROCATALYTIC DETECTION OF CYSTEINE, N-ACETYLCYSTEINE AND GLUTATHIONE BY A PRUSSIAN BLUE FILM-MODIFIED ELECTRODE

Chemically modified electrodes prepared by adsorbing prussian blue on a glassy carbon electrode are shown to catalyse the electro-oxidation of cysteine, N-acetylcysteine and glutathione in acidic media. The catalytic response is evaluated with respect to the potential scan rate, the solution pH, the concentration dependence, and other variables. Covering the electrode with Nafion(R) film improved the stability and reproducibility in liquid chromatography with electrochemical detection to the extent that repetitive sample injections produced relative standard deviations of less than 5% over several hours of operation. The limit of detection was 4 pmol for cysteine, 33 pmol for glutathione and 61 pmol for N-acetylcysteine.

Enhancement of the catalytic performance of supported-metal catalysts by pretreatment of the support

We report an interesting finding that the catalytic performance of supported Ag/SiO2 catalysts toward selective catalytic oxidation of CO in hydrogen at low temperatures can be greatly enhanced by pretreatment of the SiO2 support before catalyst preparation. Calcination of SiO2 at appropriate temperatures preferentially removes the H-bonded SiOH, which results in the highly dispersive Ag/SiO2 catalyst and thus improves the catalytic performance. (c) 2005 Elsevier Inc. All rights reserved.

Determination of ionic resistance and optimal composition in the anodic catalyst layers of DMFC using AC impedance

In the present study, a method based on transmission-line mode for a porous electrode was used to measure the ionic resistance of the anode catalyst layer under in situ fuel cell operation condition. The influence of Nafion content and catalyst loading in the anode catalyst layer on the methanol electro-oxidation and direct methanol fuel cell (DMFC) performance based on unsupported Pt-Ru black was investigated by using the AC impedance method. The optimal Nafion content was found to be 15 wt% at 75 degrees C. The optimal Pt-Ru loading is related to the operating temperature, for example, about 2.0 mg/cm(2) for 75-90 degrees C, 3.0 mg/cm2 for 50 degrees C. Over these values, the cell performance decreased due to the increases in ohmic and mass transfer resistances. It was found that the peak power density obtained was 217 mW/cm(2) with optimal catalyst and Nafion loading at 75 degrees C using oxygen. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

On the propagation rate of the chemical waves observed during the course of CO oxidation on a Ag/Pt(110) composite surface

We have analyzed the propagation rate of the chemical waves observed during the course of CO oxidation on a Ag/Pt(I 10) composite surface that were reported in our previous papers [Surf Interface Anal. 2001, 32, 179; J. Phys. Chem. B 2002, 106, 5645]. In all cases, the propagation rate v can be adequately fitted as v = v(0) + D-0/d, in which v(0) and D-0 are constants, and d is the distance between the reaction front of the chemical wave and the boundary from which the chemical wave originates. We propose that the surface species responsible for the formation of the chemical wave comes from two paths: the adsorption of molecules in the gas phase on the surface and the migration from the adjacent surface with different catalytic activity. v(0) corresponds to the contribution from the surface species due to the adsorption, and D-0/d to that of the surface species that migrates from the adjacent surface. The rate equation clearly suggests that the observed chemical wave results from the coupling between adjacent surfaces with different catalytic activities during the course of heterogeneous catalysis. These results, together with our previous reports, provide a good fundamental understanding of spillover, an important phenomenon in heterogeneous catalysis.

Catalytic oxidation of cyclohexane over Ti-Zr-Co catalysts

Ti-Zr-Co alloys have been fabricated and characterized, and their catalytic performance was discussed for the oxidation of cyclohexane with oxygen under solvent-free condition. The icosahedral quasicrystalline phase (I-phase)-forming ability of Ti-Zr-Co alloys with different compositions was discussed, and it was confirmed that I-phase could be formed as a dominating phase at the Ti-rich composition region from Ti53Zr27Co20 to Ti75Zr5Co20 in as-cast alloys. The composition and microstructure of Ti-Zr-Co alloys present crucial influences on its catalytic activity and selectivity in the oxidation of cyclohexane. The influences of some reaction parameters such as temperature, reaction time, and catalyst amounts were also investigated. Ti70Zr10Co20 alloy containing quasicrystal microstructure showed good catalytic performance with a 6.8% conversion of cyclohexane and 90.4% selectivity of cyclohexanol and cyclohexanone. It behaves as an efficient heterogeneous catalyst for the oxidation of cyclohexane and could be recycled five times without loss in activity and selectivity.

Study of CH4 and CO oxidation from electrochemical method

CH4 and CO oxidation reaction on perovskite-like oxides La2-xSrxMO4 (0.01 <= x <= 1.0; M = Cu, Ni) was investigated from cyclic voltammetry method, finding that for suprafacial CO oxidation reaction, the catalyst activity has a close correlation to the area of redox peaks measured in the cyclic voltammetry, the larger the peak area is, the higher the activity will be, while for interfacial CH4 oxidation reaction, the activity depends mainly on the difference in redox potentials (Delta E), and the smaller the difference in redox potentials is, the higher the activity will be.

Performance of Pt-TiO2 electrocatalyst for CO oxidation in the electrochemical gas sensor

It is reported for the first time that the Pt/TiO2 electrocatalyst was successfully used for the electrocatalytic oxidation of CO in the electrochemical gas sensor with a controlled potential mode. The stability of electrocatalytic activity of the Pt-TiO2 electrocatalyst for the CO oxidation is better than that of Pt.