Investigations of TiO2 photocatalysts for the decomposition of NO in the flow system - The role of pretreatment and reaction conditions in the photocatalytic efficiency

In order to investigate the photocatalytic stability and/or lifetime of tit anium oxide photocatalysts in detail, standard reference photocatalysts (JR C-TIO-5 -3, -4, and -5), of which the surface chemical and physical propert ies are well known, were studied for the photocatalytic decompositon of NO under a large-scale flow reaction system. In the first stage, the photocata lytic decomposition of NO proceeded with a high efficiency and continuous p roduction of N-2, O-2, and N2O. However, the reaction efficiency gradually decreased and finally leveled off at constant values. These values were fou nd to be in the order of JRC-TIO-4 > -3 > -5 > -2. Anatase TiO2, with a lar ge surface area and numerous OH groups, was found to exhibit a high efficie ncy for the decomposition of NO in the flow system. The optimal pretreatmen t and reaction conditions were observed at a pretreatment temperature aroun d 573 K under a mixture of O-2 and Ar. It was confirmed that the surface hy droxyl groups on the photocatalysts play an important role in the decomposi tion of NO under this flow system. (C) 2001 Academic Press.