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Differential voltammetry as well as UV-vis spectrophotometry and impedance spectroscopy were used to show that polyaniline doped with polystyrenesulfonic acid mediates the reduction of oxygen and hydrogen peroxide in aqueous media by facilitating the formation of hydroxyl radicals and increasing the sensitivity of the electrochemical method for determining the antioxidant activity of sulfur-containing amino acids. [ABSTRACT FROM AUTHOR]

The structure changes and the degree of reduction of UO after mechanoactivation in agate and stainless steel vessels in different media are studied. Clearly expressed reduction of U(IV, VI) oxide, accompanied by oxygen release as a result of mechanochemical activation is observed. The highest degree of reduction is reached when mechanoactivation is performed in suspension with nonpolar organic solvents. The presence of acetaldehyde as a reducing agent did not cause valuable increase of the reduction process. Quantitative evaluation of the mechanochemically induced changes in the crystal structure of UO is done. Decrease of the crystallite sizes of both the UO and the reduced form, provoked by the mechanochemical treatment is observed for all the samples. No other uranium-contained compounds, formed during the mechanoactivation in the different media and mixtures were found. [ABSTRACT FROM AUTHOR]

Abstract  Three cathode catalysts (60% Pt/C, 30% Pt/C and 60% Pt–Fe/C), with a particle size of about 2–3 nm, were prepared to investigate the effect of ethanol cross-over on cathode surfaces. All samples were studied in terms of structure and morphology by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Their electrocatalytic behavior in terms of oxygen reduction reaction (ORR) was investigated and compared using a rotating disk electrode (RDE). The tolerance of cathode catalysts in the presence of ethanol was evaluated. The Pt–Fe/C catalyst showed both higher ORR activity and tolerance to ethanol cross-over than Pt/C catalysts. Moreover, the more promising catalysts were tested in 5 cm2 DEFC single cells at 60 and 80 °C. An improvement in single cell performance was observed in the presence of the Pt–Fe catalyst, due to an enhancement in the oxygen reduction kinetics. The maximum power density was 53 mW cm−2 at 2 bar rel. cathode pressure and 80 °C. [ABSTRACT FROM AUTHOR]

Abstract  Corich core–Ptrich shell/C prepared by thermal decomposition and chemical reduction methods were treated by 20% H2SO4 aqueous solution and used as the electrocatalysts for the oxygen reduction reaction (ORR). The particle size range of Corich core–Ptrich shell (molar ratio of 0.92:1) on carbon powder support decreased from 3–8 to 1–6 nm when the time for the electrocatalysts immersed and treated with 20% H2SO4 aqueous solution increased from 0 to 4 h. Using Corich core–Ptrich shell (molar ratio of 0.92:1)/C treated with 20% H2SO4 from 0 to 4 h as the working electrode, the open circuit potential of ORR in 0.5 M HClO4 aqueous solution increased from 0.9995 to 1.0155 V, and the current density, mass activity, and specific activity at the overpotential of 0.1 V increased from 0.619 mA cm−2, 6.184 A g−1, and 18.614 μA cm−2 to 0.912 mA cm−2, 15.544 A g−1, and 23.413 μA cm−2, respectively. [ABSTRACT FROM AUTHOR]

Abstract  A rotating cylinder porous electrode (RCPE) of reticulated vitreous carbon (RVC) matrix was used for oxygen reduction reaction (ORR) in H2SO4 solutions. Cyclic voltammetry and hydrodynamic voltammetric techniques were used for electrochemical characterization of the ORR. Cyclic voltammograms in stationary solutions showed better performance of the anodically oxidized RVC (for periods of 1 and 5 min) for the ORR than the untreated RVC in which the first scan (ORR) after the surface treatment was of no utility, and the second scan was presented here. The hydrodynamic voltammograms obtained at the treated RCPE gave well-defined limiting current plateau with positively shifted onset potential as compared with the untreated (plain) RVC electrode. The analysis of the limiting current data on RCPE and the determination of a limiting current enhancement factor α enabled us to quantify the enhancement extent exerted by the anodic oxidation treatment. An enhancement factor of up to ∼3 was obtained at the RCPE electrode anodically oxidized for 5 min. It was found that the α slightly decreased with the rotation speed depending on the extent of anodic oxidation of RVC. This was attributed to the different mode of mass transfer (diffusion) to the interior of the micropores with different microstructure resulting from different extent of anodic oxidation. X-ray photoelectron spectroscopic and scanning electron microscopic measurements helped us to characterize the anodically oxidized RVC surface. [ABSTRACT FROM AUTHOR]

Under oxygen-rich conditions in H2 + NO + O2 mixtures, Pd/V2O5/Al2O3 catalysts are active and highly selective (∼80%) for NOx reduction to N2. In situ DRIFT spectroscopy and reactor data show that the system operates via formation of NHx species on the highly dispersed V2O5 component. Both NH3 and NH4+ are formed, with the latter dominant. The role of the palladium component is also discussed. [ABSTRACT FROM AUTHOR]