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The overpotential resistance and the entropy change of two small lithium-ion secondary batteries, which are the heat source terms to increase the battery temperature, have been measured by several methods, changing the battery temperature and the state of charge. The temperature increase and the total heat generation rate of the batteries were calculated during the discharge cycle by using the measured resistance and entropy, being compared with the experimental results of the temperature increase and the total heat generation rate. The overpotential resistance was estimated by four measurement methods, i.e., the battery voltage-current characteristics during the constant current discharge, the difference between the open-circuit voltage and the cell voltage, the voltage change during the intermittent discharge for 60 s, and the ac impedance measurement. The overpotential resistance by the voltage-current characteristics is almost the same as by the difference between the open-circuit voltage and the cell voltage. However, in some cases the resistances by the intermittent discharge and the ac impedance are smaller than the former two resistances. The entropy change ⌬S measured by the temperature change of the open-circuit voltage agrees almost with the ⌬S measured by the heat production difference between the charge and discharge cycle. The temperature increases and the total heat generation rates estimated from the overpotential resistances by the voltage-current characteristics and ⌬S by the temperature change of open-circuit voltage agree well with the measured ones for the two batteries during the constant current discharge.

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Recently the hydrogen energy system has been proposed as a countermeasure for the depletion of fossil fuel and global warming. The polymer electrolyte electrolysis cell ͑PEEC͒ can efficiently produce pure hydrogen under high current density. To design a PEEC properly and to optimize its operating conditions we have measured and analyzed the PEEC performance. Using measured overpotentials we have made a two-dimensional simulation code for PEEC. Calculated results show that the profile of current density and temperature are constant along the water flow direction, because the exothermic heat from overpotentials is almost canceled out by the endothermic heat of both entropy change and evaporation, and by heat transfer to the constant-temperature separators, resulting in a constant water-electrolyzing potential along the flow direction. The current densities measured at a segmented-electrode cell agreed well with the calculated values. By applying this simulation code to a large unit-cell with adiabatic boundary conditions, we have predicted the performance of a large stacked PEEC having an electrode length of 1 m. The predicted cell temperature and current density increase only a little along the flow direction. Under operating conditions with high pressure, the endothermic heat of water evaporation decreases greatly and the cell temperature is apt to increase downstream compared to the atmospheric operation.

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Recently, ozone is used for many purposes as an environmentally friendly oxidant. An ozone production device with high ozone concentration and low production energy is therefore desired. One candidate for such a device is ozone water production in a water electrolysis cell using a solid polymer electrolyte with PbO 2 anode catalyst. Such a device would have the advantages of being compact and producing high-concentration ozone water directly through deionized water electrolysis. We have studied ozone water production with different electrode and electrolyte compositions and operation conditions, with the aim of improving ozone production performance. The two electrolytes tested were Nafion 117 and a membrane electrode assembly ͑MEA͒ with Pt catalyst on the cathode side of Nafion 117. The two electrodes tested were a single layer of Ti expanded metal and four layers of Ti-expanded metal with different meshes. Ozone water production tests were performed for many hours with changes in temperature, water flow rate, current density, current interruption time, and other factors to optimize experimental conditions. The voltage-current characteristics of water electrolysis cell were improved significantly when the electrode was four layers of Ti-expanded metal and the electrolyte was MEA with Pt catalyst on the cathode. Stable ozone water concentration was obtained after the cell had been operated for about 8 h. The optimum temperature, water flow rate, and current density for ozone water production are 25-30°C, 33 L/h, and 1.0 A/cm 2 , respectively. Further, the noninterrupted supply of small current suppressed the performance deterioration of ozone water production by current interruption, and the ozone production energy was reduced by supply of oxygen to the cathode.Ozone has a strong oxidative power, its post-treatment is simple, and there is little secondary pollution. It is therefore used in a wide range of applications, including sterilization, oxidation, deodorization, and decolorization. Given these uses, there is a need for equipment that can efficiently produce high concentration ozone. Currently, high concentration ozone gas is first made by silent electric discharge or barrier discharge, and then dissolved in water. This ozone water is then used for sterilization or discoloration. In recent years, however, there are reports that highly concentrated ozone water can be produced directly by a solid polymer electrolyte using a PbO 2 anode catalyst. 1-5 However, the ozone production energy is high, and the production performance is not necessarily stable. Therefore, to improve the performance and stability of ozone water production by solid polymer electrolyte water electrolysis using a PbO 2 anode catalyst, we have modified the composition of the electrodes and solid polymer electrolyte and conducted experiments to optimize the operating conditions. We used multilayer electrodes with different meshes, and solid polymer electrolyte of Nafion 117 only or a membrane electrode assembly ͑MEA͒ of Nafion 117 with Pt ca...

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OH radicals play a very important role in non-thermal plasma chemical reactions for decomposition of gaseous pollutants or synthesis of methanol from methane, etc. In this paper, the CO oxidation monitoring method, which has been used in atmospheric chemistry, was examined to measure the concentration of OH radicals produced by a pulsed discharge plasma. The concentration of OH radicals in the discharge plasma of H2O/Ar mixture gas was estimated by measuring the amount of CO2 produced through oxidation of CO by OH radicals. The experimental results and the calculated results showed that it is possible to measure OH radicals using this simple method. In this experimental work, the maximum concentration of OH radicals produced by the pulsed discharge plasma of H2O/Ar was measured to be 9.4×1014 molecules cm−3 pulse−1. Within the temperature range investigated in this study (50–150°C), the formation of OH radicals increased with increase in the specific input energy (discharge energy dissipated in unit volume of the gas; SIE) value and the content of H2O; in contrast, it decreased with increase in the gas temperature.