Photocatalytic air purification

Most of the photocatalytic products currently used are applied primarily in the construction industry in order to reduce environmentally hazardous and toxic harmful substances indoors and outdoors. The standardised nitrogen oxide decomposition test according to ISO 22197-1 is used for the quantitative evaluation of these products. It can be supplemented with application-oriented VOC (volatile organic compound) analysis. Using different reactor types and geometries (flatbed reactor for planar specimens, flow-through reactor for mats or bulk goods) makes it possible to test a wide variety of products.

Determination of nitrogen oxide decomposition according to ISO 22197-1

NO-Abbaumessungen. — © Fraunhofer IST
NO decomposition measurements.

With this method, the substrate being tested is continuously exposed to the harmful substance nitrogen monoxide (NO) with simultaneous UV irradiation. The photocatalystic process oxidises the nitrogen monoxide to nitrate. When the ambient parameters (wavelength, irradiation intensity, gas concentration and conditions etc.) are known, the speed of the NO decomposition reaction permits a quantitative assessment of the tested surface’s photocatalystic efficiency.

VOC analysis of photocatalystic air purification products

Probennahme mittels Tenax-Röhrchen. — © Fraunhofer IST
Sample collection using Tenax tubes.

Investigating the decomposition of a wide variety of organic compounds and the formation of possible by-products and secondary emissions is an important aspect in evaluating the photocatalytic efficiency of air purification products. The distribution of the VOCs and their reaction process are analysed in special chamber tests, with chamber sizes ranging from a few litres to several cubic metres.

Cooperation

In the field of VOC analysis, Fraunhofer IST cooperates closely with the Material Analysis and Indoor Chemistry (MAIC) department at Fraunhofer WKI (Wilhelm-Klauditz Institute) in Braunschweig.