Construction of ZnS1-x Layers Coated Nb2O5-x Mesocrystals for Boosted Removal of Organic Contaminant

Constructing step-scheme (S-scheme) heterostructures is conducive to realizing high-efficiency charge separation. In this work, pristine Nb2O5-x mesocrystals and defects-mediated ZnS1-x layers coated Nb2O5-x heterojunctions were prepared via solvothermal-sonochemical deposition methods and applied for tetracycline degradation under visible-light illumination. The as-prepared composites were studied by several different characterization techniques. Results showed that the optimal Nb2O5-x@ZnS1-x-41 heterojunction displayed significantly improved photocatalytic activity towards tetracycline degradation, and the kinetic rate constant reached 0.01571 min−1, which was 6.41 times that of ZnS1-x and 3.09 times that of pristine Nb2O5-x mesocrystals, mainly ascribed to the formation of S-scheme carriers’ transfer pathways between ZnS1-x and Nb2O5-x mesocrystals. In addition, the trapping experiments and EPR measurements revealed that superoxide radicals and photo-generated holes were the main reactive species. Finally, possible S-scheme photocatalytic mechanism, degradation pathways, and toxicity assessment were also explored. Current work indicates some interesting ideas for design and fabricating S-scheme nanostructured composites for high-efficiency photocatalysis.