Precisely engineered type II ZnO-CuS based heterostructure: A visible light driven photocatalyst for efficient mineralization of organic dyes

• Construction of sustainable type-II Fe 3 O 4 @SiO 2 @ZnO-CuS heterojunction via simple chemical route. • Synergism of CuS nanoplates and magnetic ZnO in visible light mediated degradation process. • Magnetic ZnO-CuS degrades cationic dyes within 18 min under energy efficient LEDs. • GC–MS analysis was conducted to deduce the degradation pathway of methylene blue. • High photodegradation ability of nanocomposites retained even after five recycles. Herein, type-II band alignment of magnetic ZnO/CuS has been achieved by assembling p-type CuS nanoparticles on n-type ZnO heterostructures to accomplish the photocatalytic degradation of two colored cationic dyes, namely, methylene blue (MB) and toluidine blue (TB). The material exhibited excellent photocatalytic efficiency towards MB and TB with 93% and 87.5% degradation in just 16 and 18 min respectively. The efficacy of doped photocatalyst (FSZCS) was found to be 6 times higher than the undoped material (Fe 3 O 4 @SiO 2 @ZnO; FSZ) whereas pristine CuS degraded only 50% of the dye sample under identical conditions. Therefore, the dramatic enhancement of the photocatalytic degradation performance could be attributed to the synergetic effect created by doping CuS over magnetic ZnO nanocomposites which extended the photoresponse of ZnO by driving the entire degradation process under visible light irradiation and also reducing the charge recombination rate. The plausible mechanistic pathway and identification of degradation products was discussed in detail on the basis of scavenger studies as well as GC–MS analysis. Furthermore, the designed catalyst could be recycled and reused up to 5 runs without any significant decrease in its photocatalytic activity. The reported procedure exhibited multiple advances as it proceeded by utilizing renewable household LEDs as power source at room temperature without the use of any additional oxidant under neutral pH conditions thus, paving a strong path towards sustainable, green and responsible chemistry.