The role of carbon nanotube in zinc stannate photocatalytic performance improvement: Experimental and kinetic evidences

Abstract

The Zn2SnO4/MWCNTs (ZSC) nanocomposite was synthesized by a facile two-step process. The as-prepared nanocomposite was characterized by Powder X-ray diffraction, scanning electron microscopy, Transition electron microscopy, UV–vis diffuse reflectance spectroscopy and photoluminescence spectra analysis. The ZSC nanocomposite exhibits much higher photocatalytic activity (94% removal in 120min) in comparison with bare Zinc stannate (ZS) (17% removal in 120min) under UV-A irradiation, toward degradation of Basic Red 46. The role of the MWCNTs on the observed enhancement in photocatalytic activity was revealed by investigating the effect of radical scavengers on degradation efficiency. The addition of BQ had no effect on photocatalytic efficiency and t-buthanol decreased the photocatalytic activity to some extent. However, the addition of iodide ion, as a hole scavenger, inhabited completely the photocatalytic degradation of BR46, indicating that the degradation of the BR46 occurs mostly by direct oxidation on photogenerated holes. Based on the results of experiments, DRS and PL spectra, two possible mechanisms were proposed. Moreover, a new kinetic model was developed based on the intrinsic elementary reactions and the proposed mechanism. The correlation coefficient (R2) and root-mean-square-error (RMSE) of 0.990 and 7.12×10−4 indicates the good agreement between the calculated apparent rate constants and experimental ones.