Photocatalytic degradation of alachlor using type-II CuS/BiFeO3 heterojunctions as novel photocatalyst under visible light irradiation

In this study, a sustainable visible light promoted photocatalytic route has been developed for mineralization of alachlor pesticide using CuS/BiFeO3 heterojunction materials. The heterojunctions were synthesized by a two-step process and characterized using XRD, FESEM, HRTEM, XPS, FTIR, UV-Vis-DRS and PL techniques. Morphologically, the heterojunction materials consist of BiFeO3 nanoplates with high aspect ratio and CuS nanorods. The intimate contact between the two phases was ascertained from the HRTEM study. Optical property study suggested that these materials show excellent absorption in visible region with superior charge carrier separation characteristics compared to the individual components. The transient photocurrent measurement and I-V plots revealed high mobility of the excitons across grain boundary due to heterojunction formation. The band positions of the two components were aligned favourably for a cyclic movement of electrons and holes resulting in a type-II heterojunctions. The CuS/BiFeO3 materials efficiently catalyse the mineralization of alachlor pesticide under visible light illumination achieving > 95% degradation within 60 min. The mechanism of alachlor degradation over the catalyst surface was elucidated using GCMS and radical scavenger experiments. The attractive features of the developed photocatalytic method are the use of renewable energy, low cost, high efficiency, stability and recyclability of the catalyst material.