Investigation of photocatalytic degradation of crystal violet and its correlation with bandgap in ZnO and ZnO/GO nanohybrid

Abstract

The photocatalytic efficiency of semiconducting catalytic material is greatly influenced by one of the important factor like band gap. In the area of sustainable energy and environmental decontamination, ZnO photocatalysts have been extensively used. However, there is a significant decrease in the photocatalytic performance of ZnO due its large band gap, and fast recombination of charge carriers. Various methods have been designed to address this issue, such as nanostructuring, chemical doping, introducing oxygen defects, surface sensitization, and employing nanocomposites. Here, the semiconducting ZnO, ZnO/GO were prepared by simple co-precipitation method and solid state reaction respectively. The synthesised ZnO, ZnO/GO catalysts were characterized thoroughly by different techniques such as X-ray diffraction (XRD), Raman spectroscopy, Fourier Transform infrared Spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Diffuse reflectance spectroscopy(DRS), photoluminescence (PL), BET specific surface area. The Eg values of ZnO/GO has found to be 2.71 eV which is lower than the bare ZnO (2.81 eV), which is benefit to have higher photocatalytic activity. The performance of synthesized catalysts was explored for remediation of CV dye by employing visible light as energy source to begin photoreaction. The ZnO/GO nanohybrid has shown 99% degradation of CV in 240 min under neutral pH and rate constant found to be 0.01514 min−1 which is much higher than bare ZnO. In ZnO/GO nanohybrid, the phenomenal photocatalytic efficacy was attributed to the suppressed charge carriers (electron in CB and holes in VB) recombination and adequate injection of photosensitized electron in the hybrid during the photocatalytic reaction. Further, GO itself acts as electron collector and transporter and thereby furnishes electrons for enhancing the photocatalytic reaction by providing reactive oxygen species and hydroxyl radicals for the degradation of crystal violet. Addtionally, the interrelationship between the physical properties like band gap and catalytic competence were founded.