Effect of nitrogen-plasma surface treatment to the enhancement of TiO2 photocatalytic activity under visible light irradiation

A visible-light-active commercial TiO2 powder was prepared by thermal nitrogen-plasma processing as the surface treatment. The photoactivity of the treated TiO2 samples was evaluated in the photocatalytic degradation of gaseous 2-Propanol (IPA) in a batch reactor. XPS analysis showed that oxygen vacancies formed in the lattice of the treated TiO2 particles and no nitrogen peaks were detected. With increasing the treating time, the visible absorbance and oxygen vacancies were increased but the surface area of treated sample was decreased. The photodegradation rate of IPA under visible light illumination depended strongly on the treating time of the catalyst, and the photoactivity of the treated sample was higher than that of plain TiO2. From the results of reaction rate constant and mineralization yield of IPA, it was found that the TiO2 powders treated for 30 min demonstrated the highest photocatalytic activity among all samples. This high visible light photoactivity was ascribed to an intermediate level of visible absorbance as well as optimal oxygen vacancies after the thermal nitrogen-plasma surface treatment. (c) 2006 Elsevier B.V. All rights reserved.