Two-step hydrothermal synthesis of novel hierarchical Co3O4/Bi2O2CO3p-n heterojunction composite photocatalyst with enhanced visible light photocatalytic activity

Abstract

A hierarchical flower-like Co3O4/Bi2O2CO3 composite photocatalyst with a p-n heterojunction semiconductor structure has been synthesized via two-step hydrothermal process. The composite photocatalyst have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), BET surface area, UV–vis diffuse reflectance spectra (DRS), electron spin resonance (ESR) and photoluminescence spectroscopy (PL). The photocatalyst exhibits enhanced photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The ESR results reveal that the superoxide radicals (O2−) were the main active species in the photocatalytic system. The 0.6wt% Co3O4/Bi2O2CO3 exhibits the highest photocatalytic activity as compared with other samples because of the formation of the p-n junction between p-Co3O4 and n-Bi2O2CO3, which effectively suppresses the recombination of photoinduced electron-hole pairs and increase of the concentration of superoxide radicals (O2−) involving in the photodegradation process. Moreover, the mechanism of the enhanced photocatalytic properties was proposed.