Fabrication of novel Z-scheme InVO4/CdS heterojunctions with efficiently enhanced visible light photocatalytic activity

Novel Z-scheme InVO4/CdS heterojunction photocatalysts have been successfully synthesized for the first time via a microwave-assisted process, followed by a mild hydrothermal method. The crystal structures, morphologies and sizes, chemical compositions and optical properties of the prepared photocatalysts were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and photocurrent measurements. Results showed that the prepared InVO4/CdS heterojunctions were composed of about 15 nm InVO4 nanoparticles and 1.5 μm CdS microspheres, and all heterojunctions exhibited good photoabsorption in the visible light region. The photocatalytic activity of the obtained samples was carefully evaluated via the degradation of rhodamine B (RhB) and ciprofloxacin (CIP) under visible light irradiation (λ > 420 nm). Compared to that of bare InVO4 and CdS, the InVO4/CdS heterojunctions exhibited significantly enhanced photocatalytic activity for RhB and CIP degradation. Moreover, the 40 wt% InVO4-coupled CdS composite displayed the highest catalytic efficiency for RhB photodegradation, which is about 59.4 and 4.8 times higher than that of pure InVO4 and CdS, respectively. In addition, the active species trapping experiment and electron spin resonance (ESR) measurement demonstrated that h+ and ˙O2− radicals were the predominant active species in the photocatalytic reaction process. Furthermore, the possible enhanced photocatalytic mechanism of InVO4/CdS heterojunctions was also proposed based on the band position measurements and ESR analysis.