New Research


Design of Photofunctional Materials

-Photocatalytic transformations by Sunlight-

Prof. Takayuki Hirai, Associate Prof. Yasuhiro Shiraishi

Our group aims at the design of photofunctional materials, especially for optical sensors and photocatalysts driven by light energy. The optical sensors include the chemosensors that quantitatively detect trace levels of environmental pollutants by absorption and fluorescence analysis. The photocatalyst studies aim at selective transformation of molecules by catalytic reactions driven by light energy.

Photocatalysts promote clean oxidation and reduction reactions just by absorbing light; however, the promotion of targeted reaction is usually very difficult. In the photocatalytic reactions, the use of renewable sunlight is a very important task because it, if achieved, facilitates clean and energy saving transformation. The most important point is the use of visible region light (400-800 nm); however, this is very difficult to achieve. The design of photocatalytic systems that produce valuable chemicals with earth abundant resources is therefore very important subject.

Hydrogen peroxide is a clean oxidant that produces water as a byproduct, which is a versatile chemical for pulp bleaching and disinfection. Recently, we have synthesized organic semiconductor consisting of carbon, nitrogen, and oxygen (see picture). These photocatalyst powders, when added to water and photoirradiated by sunlight with molecular oxygen, successfully produce hydrogen peroxide. This is the first report of hydrogen peroxide production from water and molecular oxygen by renewable sunlight. Our results indicate that the reactions that have long been considered as impossible can be facilitated by new catalyst design.

Hirai Lab. HP
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