Stably Photocatalytic Decomposition of Rhodamine-B by Samarium Doped ZrO2-ZnO Composite under Simulant Solar Light Irradiation

The Sm-ZrO2-ZnO catalyst prepared by hydrothermal method is proved to be superior in stably photocatalytic degradation of Rhodamine-B under simulant solar light irradiation. Sm doping improves the ultraviolet and visible light absorbance. Composition of ZnO with ZrO2 leads to enhancement of ultraviolet light absorbance, change of the ZnO morphology from nano-granule to rod and good dispersion of nano-ZrO2 particles over ZnO rod surface. The last is regarded as key to keep stable activity for the catalyst. The high photocatalytic activity is ascribed to the p-n heterojunction formation and uniform distribution of fine ZrO2 particles over ZnO. This morphology plays an import role in light absorption and enhances the separation of photo-generated electron-hole pairs. Introduction Heterogeneous photocatalysts, such as TiO2, the most popular photocatalyst with an efficient electron transfer process, offer great potential for mineralization of organic pollutants [1,2]. Zinc oxide (ZnO) is another most promising photoactive oxides for decomposition of contaminants [3,4]. As a n-type semiconductor, ZnO presents unique characteristics, such as wide band gap (3.37 eV) in the near-UV spectral region [2,4], strong oxidation ability, good photocatalytic property and a large free-exciton binding energy (60 meV) [3]. Under a certain conditions, the performance of ZnO is superior to TiO2 in quantum efficiency and photocatalytic activity [1]. However, the defects of ZnO include low utilization of solar energy, photocorrosion, low migration rate and high recombination rate of the photoelectron and hole pairs, which limit its application. As a semiconductor, ZrO2 has been considered as a photocatalyst in different chemical reactions due to its relatively wide band gap (5.1 eV) and low negative valence band potential [5]. Although ZrO2 possesses characteristics of favorable chemical and thermal stability and surface acidity, it is only motivated by the light below wavelength of 250 nm. It is relatively rarely utilized in photocatalytic degradation of organics compared with TiO2 and ZnO. In order to improve the heterogeneous photocatalysis activity under UV/visible/solar illumination, considerable effort has to be exerted to improve the immigration of photo-induced charge carriers. Amoung these methods, metal doping and binary oxide photocatalyst system have gained much attention [6,7]. On the other hand, there have been studies indicated that the structural and morphology characteristics of ZnO and ZrO2 play an important role in photocatalytic activity of the catalysts [8,9]. Consequently, it is significant to research the composition of ZnO and ZrO2 doped with metal oxides about its morphology and granularity properties and the effect on photocatalytic performance. There has been rare researches about the composited and doped compounds. Herein, ZrO2-ZnO composite oxides was prepared via hydrothermal method and doped with samarium cations. The improvement of its stably activity in photocatalytic degradation of Rhodamine-B under simulant solar light irradiation was tested. The differences arise from the 7 Copyright © 2018, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering Research (AER), volume 174 International Conference on Energy Development and Environmental Protection (EDEP 2018)