Determination of dissolved oxygen by catalytic reduction on Nafion-methyl viologen chemically modified electrode.
A small size Nafion-methyl viologen chemically modified electrode (Nafion-MV CME) together with a small size electrolytic cell were constructed for the purpose of dissolved oxygen (DO) determination. The catalytic reduction of DO on Nafion-MV CME results in fast and sensitive DO determination. The mechanism of such detection is also considered.
Catalysis of dioxygen reduction at glassy carbon and carbon fibre electrodes coated with poly-cobalt(O-aminophenyl)porphyrin film
Abstract Electrooxidation of tetra(O-aminophenyl)porphyrin (H2Co-TAPP)) in acetonitrile results in the formation of a polymer film on glassy carbon (GC) and carbon fibre (CF) surfaces. These films can be made electrocatalytically active toward dioxygen by metallization with Co(II). The film coverage of electroactive cobolt porphyrin are 1.1 ∼ 1.4 × 10−9 mol cm−2. Dct determined by chronoamperometry are 8.4 × 10−12 and 5.5 × 10−12 cm−2 s−1 in 0.05 M H2SO4 and 0.05 M phosphate buffer respectively. Cyclic voltammetry, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) have been used to characterize these films. The polymer film electrodes are stable in organic and aqueous solution under various acidic and basic conditions and catalyze dioxygen reduction to produce hydrogen peroxide at + 0.15–+0.20V (vs Ag/AgCl. sat. KCl) in acidic media. The activity of such polymer film electrodes decreases only by 10% when repetitively cycled between the potentials of +0.6 to −0.6 V vs Ag/AgCl. sat. KCl) for 100 scan or more at a scan rate of 100 mV s−1.
Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier
Biomass gasification is an important method to obtain renewable hydrogen. However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11MJ/Nm3 for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16gH2/kg biomass. For biomass oxygen/steam gasification, the content of H2 and CO reaches 63.27–72.56%, while the content of H2 and CO gets to 52.19–63.31% for biomass air gasification. The ratio of H2/CO for biomass oxygen/steam gasification reaches 0.70–0.90, which is lower than that of biomass air gasification, 1.06–1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.