Water management of the catalyst layer in a polymer electrolyte membrane fuel cell was improved by focusing on the three-phase boundary. To fabricate the cathode catalyst layer, carbon-support with catalyst and fluorine resin were mixed and heat-treated at the melting temperature of fluorine resin. The transmission electron microscopy images of this electrode catalyst showed that the surfaces of the catalyst particle and of the carbon-support were partly coated by thin film of melted fluorine resin. Ionomer electrolyte material was added to this electrode catalyst, and an electrode catalyst with a four-layer structure was fabricated. The durability at 50°C of a single cell using the four-layer electrode catalyst as the cathode was examined. The deterioration rate was lower than that using the conventional three-layer electrode catalyst. In addition, a load change test at 50°C, an OCV test at 50°C, and a durability test at room temperature gave good results.

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The wastewater of paint booths is generally reused for cost purposes. So, the circulating water gives off an offensive odor due to the reproduction of microorganisms. Very recently, the electro-conductive diamond was developed as a new electrode material and has high oxidation characteristics due to its inherent chemical stability. Therefore, we studied odor abatement of paint booths wastewater by electrolysis using an electro-conductive diamond. As a result, n-butyric acid which was the main odor-causing component was decomposed, and it was found to be possible to reduce the odor causing agent. However, the problem in which scales formed on the cathode arose in long-time electrolysis. Then, we tried the combination of the irradiation of the ultrasonic wave and the direction change of the current for improvement of this problem. It was found that the adhesion of the scale to the cathode could be prevented by ultrasonic irradiation and reverse polarization of voltage.

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The size, size distribution, and stability of hydrogen nanobubbles generated in the catholyte of a potassium carbonate solution, i.e., alkaline electrolyzed water, were determined using a dynamic light scattering method. Results show the following: 1) Hydrogen nanobubbles existed stably for 24 h in the closed system. The average size of the nanobubbles 5 h after their generation was 160 nm. It was 184 nm after 24 h. Some of them combined to form 5–10 µm diameter bubbles. 2) In an open system, hydrogen nanobubbles were present even after 24 h; the Ostwald ripening phenomenon was observed. That is, although some nanobubbles dissolved and vanished into the solution by ripening, others grew to over a micrometer. Therefore, their distribution range widened during ripening.

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