Solvothermal synthesis of CoO/BiVO4 p-n heterojunction with micro-nano spherical structure for enhanced visible light photocatalytic activity towards degradation of tetracycline

A noble-metal-free CoO/BiVO4 p-n heterojunctions with micro-nano spherical structure were synthesized via a simple solvothermal method. The morphology, crystal structure, composition and properties of the as-prepared samples were investigated by XRD, SEM, TEM, UV–vis and XPS. 30 wt% CoO/BiVO4 sample revealed the most excellent photocatalytic activity of TC (87.3 %, 90 min). The degradation rate constant was 0.022964 min−1, which was 3.72 and 2.54 times higher than pure CoO and BiVO4. The enhanced photocatalytic activity and stability are due to decorating CoO on BiVO4 avoid deactivating caused by serious agglomeration and the formation of the built-in electric field which could improve the separation efficiency of photogenerated carriers with an apparent quantum efficiency of 0.54 %. Furthermore, the photocatalyst were reused for five cycles and remained 95.7 % of the raw sample, indicating it has the extraordinary stability and reusability. The study on photocatalytic mechanism proved that O2- and h+ were the primary species in photocatalytic system.