Zn/N co-doped TiO2 Nanotubes for Enhancement of Photocatalytic Degradation of Pentachlorophenol
Xing Hong, Lihong Wu, Xiaohui Li
Abstract
The purpose of this research was to synthesize mono-doped (Zn/TiO 2 , N/TiO 2 ) and co-doped TiO 2 (Zn/N co-doped TiO 2 ) nanotubes by the sol-gel method and use them as photocatalysts for the photocatalytic degradation of pentachlorophenol (PCP). Structural analyses by SEM and XRD indicated successful mono-doping and co-doping of TiO 2 nanotubes, and optical studies by UV–vis absorption spectra revealed that the optical band gap values of TiO 2 , Zn/TiO 2 , N/TiO 2 and Zn/N co-doped TiO 2 nanotubes were estimated at 3.29, 3.25, 3.21 and 3.16 eV, respectively, indicating the band gap of TiO 2 decreased after mono-doping and co-doping with N and Zn. The results of the EIS analyses showed that Zn/N co-doped TiO 2 nanotubes with the lowest charge transfer resistance towards pure and mono-doped TiO 2 can accelerate the interfacial photo-excited charge carrier transfer rate. Studying the photocatalytic activity of the prepared photocatalyst for degradation of 50 ml of 40 mg/l PCP solution upon simulated solar light irradiation showed that the time required of TiO 2 , N/TiO 2 , Zn/TiO 2 and Zn/N co-doped TiO 2 nanotubes for complete degradation of PCP molecules were 250, 200, 185 and 155 minutes, respectively. The highest rate of photodegradation of PCP solution was observed for the co-doped TiO 2 nanotubes due to the formation of an intermediate band in the energy band-gap of co-doped TiO 2 , which has a beneficial synergistic effect by lowering the recombination of photo-excited carriers and increasing visible light absorption.