Development of Visible Light Photocatalyst
with Superior Durability and High Catalytic Activity, 'Fresh Green'- BackgroundPhotocatalyst films with deodorant, antibacterial, antifogging, and self-cleaning effects are
generally formed by titanium oxide solution spray coating or spin coating, or by dipping things in atitanium oxide solution. Therefore, photocatalyst films generally have poor durability and areconsequently difficult to apply on surfaces subjected to a high degree of surface sliding or scratching.
In order to use photocatalyst films indoors, it is important for them to be able to absorb visible light.
A titanium oxide film, super durable and in response to visible light, is able to available at the
inaccessible location or in the room under weak-ultraviolet rays.
- Objectives
This study is intended to develop an innovative titanium oxide film with superior durability inresponse to visible light, and to characterize the film for practical use.
- Principal Results(1) Carbon-doped Titanium Oxide Films and Characterization of Crystalline Structure
The carbon-doped titanium oxide films (hereinafter referred to as ‘Fresh Green’) were formed byoxidizing and carbonizing titanium surface (patent pending). The XPS analysis of Fresh Green film
indicates a significant peak at the binding energy for Ti-C through the entire depth of the film up to thematrix boundary (Fig-1). The peak at the binding energy for Ti-C was observed in Fresh Green filmwith annealing process as well.
(2) Durability and Spectral Absorbance
Following features were found by durability tests and spectral analysis of Fresh Green:・Hardness : higher than a hard chromium plating (Fig-2)
・Wear Resistance : no remarkable wear by SiC ball-on-disk test
・Scratch Resistance : higher exfoliation load than TiN・Heat-Resistance : no degradation of photocurrent and wear at 470℃
・Corrosion Resistance : corrosion resistance with 1M H2SO4 and 1M NaOH aqueous solution
・Water Splitting : more than 6% quantum efficiency below 400nm wavelength・Spectral Absorbance : absorbance up to 490nm, cf. 410nm for commercial products (Fig-3)(3) Deodorant Effect and Anti-Contamination Effect
In order to assess sick house syndrome, a deodorant test was carried out. The decomposition rateof acetaldehyde by Fresh Green was more than two times higher than that by commercial products(Fig-4). In order to investigate specimen contamination, Fresh Green and commercial productspecimens were placed in a room for smokers for 145 days. The surface was illuminated by afluorescent light, but free of direct sunlight. After the test, the commercial product was stained with fat
and had a pale yellow color. The surface of Fresh Green, however, remained unchanged and wasclean (Fig-5). The fact clearly indicates that Fresh Green can oxidize and decompose the stains.
- Future Developments
We are developing the Fresh Green process further to have higher photocatalytic activity for the
purpose of practical use.
- Main Researcher：Masahiro Furuya, Research Scientist, Sector, Nuclear Power Generation
Technology, Nuclear Technology Research Laboratory- Reference
M. Furuya et al., 2004, “Development of Visible Light Photocatalyst with Superior Durability andHigh Catalytic Activity, 'Fresh Green',” CRIEPI Report T03067, in Japanese.

Copyright © 2004, CS Promotion Office, CRIEPI, JapanC–H(C) bondIntensity, (a.u.)

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Water Spliting Efficiency η (%)

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Acetaldehyde Concentration, w (ppm).

Deodorant Effect under
Visible Light Irradiation(b) Fresh Green
Fig-5 Surface Appearances after
Field Contamination Test

Copyright © 2004, CS Promotion Office, CRIEPI, Japan