A research team led by Hisashi Hagiwara and Tatsumi Ishihara of Kyushu University developed a photocatalyst that generates 1,000 times more hydrogen from water than the existing photocatalyst. The research members improved the surface of the material to utilize the optical wavelength that accounts for 50% of sunlight. A photocatalyst resolves water into hydrogen and oxygen. It is usually made of an oxide of titanium or tantalum. They covered the surface of fine particles of tantalum oxide with an organic dye that absorbs optical wavelength similar to the dye used for the photosynthesis of a plant. That is, the dye absorbs optical wavelength and the oxide absorbs ultraviolet that passes the dye.
In the experiment, they put fine particles of several hundred nanometers in diameter each into water and radiated experimental light about 10 times stronger than sunlight. While the existing fine particles generated about 0.05 ml of hydrogen gas per hour, the new technology successfully generated about 50 ml of hydrogen gas per hour that is 1,000 times more than the existing fine particles. In addition, they confirmed that the surface of the new type fine particles is hard to deteriorate, though an organic substance is generally liable to be destroyed when ultraviolet light is radiated on it. Mathematically, it is possible to generate about 30 liters of hydrogen a day if one kilogram of the new photocatalyst is put into a water tank installed outside. The research team plans to increase the amount of hydrogen generated daily from 30 liters to 600 liters to make the new technology applicable to a fuel cell in alliance with private companies.