In direct methanol fuel cells, methanol crossover causes not only a loss of methanol fuel but also a reduction of the open circuit voltage. We have developed a rapid evaluation of methanol crossover through a proton exchange membrane by utilizing a Pt-microdisc electrode. The equipment consisting of a Nation film sandwiched by a pair of PTFE sheets was put into a set of glass cells. The reservoir cell was filled with 0.5 M H2SO4, which contains methanol in various concentrations, and the opposite receiver cell was filled with 20 ml of 0.5 H2SO4, which also included the Pt-microdisc electrode, a counter electrode and a reference electrode. By making contact of the Pt electrode with the membrane, methanol-oxidation current-potential curves were measured to evaluate the crossover. The crossover on the Nation surface was assessed to be 60% of the reservoir methanol concentration. Consequently, the developed equipment quickly and successfully evaluates the methanol crossover.
The reaction of titanium diisopropoxide bis(acetylacetnate) and titanium tetraisopropoxide with several organic diols gave novel linear and net-worked alternative titanium-organic moietes hybrid copolymers. The forms and sizes of the net-worked alternative titanium-organic moietes hybrid copolymers were found to vary with the organic units. The UV-VIS and ESR spectra of the products were taken to estimate their electronic properties. The UV-VIS spectra of both linear and net-worked hybrid copolymers having conjugated organic moieties were found to appear at longer wave lengths, and further their ESR spectra indicated a peak due to the organic radical spieces. These results strongly suggested that an electron transfer from the aromatic moieties to the titanium atom occurred in the alternating hybrid framework. The signal intensities of the ESR spectra were shown to increase in the net-worked system compared with the linear system. To investigate the electron transfer process, the ab-initio calculations of the monomer models were done, indicating that in the models having the conjugated organic groups the HOMO is delocalized on the organic moieties, while the LUMO is localized on the titanium atom by analyzing the LCAO coefficients of the models. It was thus deduced that the electron transfer occurs from the organic moiety to the titanium atom with reduction of titanium from + 4 to + 3.
Ability of several ceramic triggers to generate plasma has been investigated upon irradiation of 2.45 GHz microwave in pure water and in an aqueous solution of dichloroacetic acid or β-naphthol. After the liquids started boiling due to absorption of microwave power by water molecules, plasma was generated in the restricted vapor phase between the solid triggers and the surrounding liquid. When SiC and carbon block were used as a trigger, O and OH radicals were observed in the generated plasmas, but H radicals were formed preferentially when the trigger was La0.8Sr0.2CoO3 or La0.6Sr0.4MnO3. Dichloroacetic acid or β-naphthol could be decomposed by the plasma treatment, though volatile partial decomposition products were also formed. Decomposition of β-naphthol was more effective than that of dichloroacetic acid, especially when SiC was employed as a trigger. Thus, the present study confirmed the potential use of microwave-induced plasma for treating waste water.
Au-Sn alloys ranging in Sn content from 15 to 46 atom% were electrodeposited from a newly developed sulfite-pyrophosphate bath (1 M sodium sulfite +0.2 M potassium pyrophosphate +0.05 M sodium tetrachloroaurate (III) +0.02 M stannous pyrophosphate (II) that did not contain cyanide. Codeposition behavior was investigated electrochemically. Electrodeposition was conducted under both galvanostatic and potentiostatic conditions. The composition, surface morphology, and phase structure of the electrodeposits were studied. Codeposition of gold and tin occurred at a potential between the potentials of gold and tin deposition. Tin content in the deposits increased with increasing current density. Au-Sn alloys with a composition near the eutectic composition (Au-29 atom%Sn) were obtained under both galvanostatic and potentiostatic conditions. The electrodeposited Au-Sn alloys consisted of single phase of ζ' phase (Au5Sn phase) or of ζ' and δ phases (AuSn phase).
Origin of enhanced electrochemical oxidation of glucose observed around 0.3 V (vs. Ag/AgCl (KCl sat.)) on an Hg adatom-modified Au polycrystalline electrode in alkaline aqueous solutions was investigated by cyclic voltammetry in various potential regions and solution pH's. The enhanced oxidation current was stable under continuous cycling between - 0.55 and 0.35 V. Positive scanning of potentials to greater than 0.35 V caused the oxidation current to decrease with dissolution of the UPD adlayer of Hg from the Au electrode. The surface structure of the Hg adatom-modified Au electrode found to be highly important in glucose oxidation. Moreover, pH dependence of the enhancement of glucose oxidation was attributed to the amount of adsorbed OH- on the Hg adatom-modified Au electrode. The investigation revealed that the surface structure on the Hg adatom-modified Au electrode cased an increase in the amount of adsorbed OH- on the Hg adatom-modified Au electrode around 0.35 V. It was considered that OHad produced by partial discharge of OH- on the Hg adatoms and/or oxide layer (Au(OHad)) of Au surface catalyzed the oxidation of glucose on the Hg adatom-modified Au electrode.
Membranes based on tungstic acid and poly(vinyl alcohol) hybrid compounds (W/PVA membranes) were synthesized by a low cost aqueous neutralization process, and proton conductivity, water resistance, swelling and methanol permeability were examined. The W/PVA membranes exhibited conductivity of 3.6 ×10-3 Scm-1 at 80°C and 90% relative humidity, in addition to a sufficient hot water resistance. By a treatment with iso-butyraldehyde, swelling of the W/PVA membranes was remarkably reduced, and methanol permeability for the membranes with the iso-butyraldehyde treatment is far lower than that of Nafion® 117. The W/PVA membranes are promising as an electrolyte for direct methanol fuel cells and others.
Tokyo Electric Power Company, Inc. (TEPCO) and NGK Insulators, LTD (NGK) have developed Sodium Sulfur (NAS) Battery. Outstanding feature of the battery is high durability of the charge and discharge cycles. This report presents the electrical performance change of NAS Battery and internal inspection. It is said that degradation of NAS battery is closely related to the protection layer on sulfur case. In this reports it is revealed that the degradation is caused by the two kinds of resistance rise. One of them is ohmic resistance rise which leads to the charge-discharge efficiency loss. We has reached conclusion that resistance rise is caused by the corrosion products formed on the sulfur case. The other is polarized resistance rise which leads to capacity loss. This polarized resistance rise, seen in only 2-phase-region during charge, is caused by corrosion products solved into sulfur electrode.