Comparison of supported TiO2 catalysts in the photocatalytic degradation of NOx

• Surface area appears to be a determining factor for the activity of the photocatalysts.
• No significant enhancement in activity was observed above a load of 1.16 mg cm−2.
• Different mechanisms seem to occur in presence and absence of humidity.
• PC500 gave the best results in dry air.
• Kronos responded better to the presence of humidity and performed well in Vis.

A comparison is made in this study of the effectiveness of various commercial catalysts in the oxidation of NOx by heterogeneous photocatalysis. The following catalysts were considered: Aeroxide TiO2 P25, Aeroxide TiO2 P90, Hombikat UV-100, Kronos vlp7000, CristalACTIV PC105, CristalACTIV PC500, Kemira 650 and Anatasa Aldrich. All catalysts were deposited by a dip-coating technique onto borosilicate 3.3 glass plates. Optimization of catalyst load showed no significant enhancement of photoactivity, in general, above a deposited mass of 1.16 mg cm−2. Differences between photocatalyst activity were more apparent at longer illumination times. Photoactivity decreased in the presence of humidity and differences in the adsorbed products were detected. Photocatalyst activity was strongly influenced by specific surface area, with the best results obtained by the catalysts with the largest surface area, namely the PC500, Hombikat and Kronos. Photocatalyst stability was demonstrated in successive reuse cycles.

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