Effects of O 2 and H 2 O 2 on TiO 2 Photocatalytic Efficiency Quantified by Formaldehyde Formation from Tris(hydroxymethyl)aminomethane

Author: Diesen Veronica  

Publisher: Science and Technology Network Inc.

ISSN: 1203-8407

Source: Journal of Advanced Oxidation Technologies, Vol.16, Iss.1, 2013-01, pp. : 16-22

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Abstract

The impact of O2 and H2O2 on the efficiency of TiO2 photocatalysis has been studied in this work. Tris(hydroxymethyl)aminomethane (Tris) was used to probe the efficiency. Upon hydrogen abstraction by e.g. hydroxyl radicals from Tris, formaldehyde is formed. This product was detected and quantified using a modified version of the Hantzsch method. A significant increase in the formaldehyde production rate was observed upon addition of O2 or H2O2. It was also found that O2 and H2O2 are equally effective in scavenging the photo-excited electron, which is probably a result of their similar adsorption properties. A strong concentration dependence, independent of O2 or H2O2 content, was found at low Tris concentrations (< 100 mM). Adsorption studies of H2O2 onto the TiO2 surface were performed in order to explore the rate controlling reactions. The results show that H2O2, having a stronger adsorption affinity than Tris towards the photocatalytic surface, govern the kinetics, but only until a monolayer is built up.