Self-cleaning photocatalyst

The oxidative degradation of organic pollutants in water and air streams is considered as one of the so-called advanced oxidation processes. Photocatalytic decomposition of organics found widespread industrial interest for air purification (e.g., decomposition of aldehydes, removal of NO , ), deodorization, sterilization, and disinfection. Domestic applications based on Ti02 photocatalysts such as window self-cleaning, bathroom paints that work under illumination with room light, or filters for air conditioners operating under UV lamp illumination have already been commercialized. Literature-based information on the multidisciplinary field of photocatalytic anti-pollutant systems can be found in a number of publications, such as Bahnemann s [237, 238] (and references therein). 

Applications of titania nanotube arrays have been focused up to now on (i) photoelectrochemical and water photolysis properties, (ii) dye-sensitized solar cells, (iii) photocatalysis, (iv) hydrogen sensing, self-cleaning sensors, and biosensors, (v) materials for photo- and/or electro-chromic effects, and (vi) materials for fabrication of Li-batteries and advanced membranes and/or electrodes for fuel cells. A large part of recent developments in these areas have been discussed in recent reviews.We focus here on the use of these materials as catalysts, even though results are still limited, apart from the use as photocatalysts for which more results are available. 

The role of photocatalysis by transition metal complexes in the environment is reviewed, and its influence on composition of the environmental compartments, transport between them, and activation of the environmental self-cleaning behavior is characterized. In description of atmospheric processes, the attention is paid to coordination compounds as photocatalysts of the transfer and redox reactions of nitrogen oxides. In the case of hydrosphere and soils, various mechanisms of organic pollutant photodegradations are presented in which the iron, copper, and chromium complexes play... 

Photocatalysis is classified into two categories. One is of apphcation to the improvement of living environment such as anti stain, self-cleaning, and superhydrophilicity [1]. Ti02 photocatalysts are widely used for these applications and many industrial products have been made. Another direction of... 

Materials for air cleaning Self-Cleaning, Antibacterial Room air cleaner, Photocatalyst-equipped air conditioners and interior air cleaner for factories. Outdoor air purifiers Concrete for highways. Roadways and footpaths. Tunnel walls. Soundproof walls and building wahs... 

With the help of natural powCT of sunlight and rain, the photocatalyst displays the self-cleaning action by decomposing and removing organic matters, based on the super-hydrophilic phenomenon. It is called photocatalytic cleaning (self-cleaning) action. 

The Self-Cleaning Effect of the Glass with Photocatalyst Film... 

Tanaka H., Tanaka K., Obana S., Tsujimoto A., Tamaru H., Takahama K. The self-cleaning performance of photocatalytic cleaning glass CLEARTECT and its evaluation. In collection of summaries of the 9th Photocatalyst Symposium Summaries, Photo-Eunctionalized Materials Society, Tokyo University, December 2002, pp. 198-199... 

For the past 20 years, the technology of TiO photocatalyst or photocatalysis has progressed rapidly, and become very attractive in the development of construction materials like ceramic tiles, blocks, glass, paints... with self-cleaning, air or water purification and antibacterial functions. As a result, various construction materials are being developed by utilizing the TiO photocatalysis. A broad list of possible applications of photocatalytic cementitious materials can be summarized as follows [11] ... 

Recently, photocatalyst coating technology enabled to produce construction materials having advanced functions such as sterilizing, deodorizing and self-cleaning properties. 

One of the most popular applications of photocatalyst is for its self-cleaning capability in exterior construction materials of buildings. There are various exterior finishing materials treated with photocatalyst on the Japanese market at present. 

Antibacterial, deodorizing and self-cleaning functions of photocatalyst derive from the organic compound decomposition ability of active oxygen, generated from photocatalytic reaction. For the purpose of improving oxidative degradation activity, it is essential to reduce the recombination of photo-excited electron-hole pair. 

The advantages of the photocatalyst applied in exterior materials he in esthetic preservation, reduction of hfe cycle costs (LCC) including cleaning cost. Figure 4.3 shows a comparison of the self-cleaning properties of exterior tiles actually installed. Since their release in October 1998, photocatalyst tiles have proved so successful that they have been introduced to more than 5,000 projects to date. 

Among various application fields of TiO photocatalysis in construction, building finishing materials with self-cleaning ability are most popular. Some prefabricated house manufacturers supplied new type of houses with photocatalyst-coated tile finishing or external finishing boards on the market a few years ago. 

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