CeO₂ nanoparticle-modified BiOI nanoflowers as visible-light-driven heterojunction photocatalyst for tetracycline degradation and antibacterial

BiOI, a typical narrow-band gap visible-light-driven photocatalyst, possesses a high recombination rate of photogenerated electrons and holes, which hinders its practical application in environmental remediation. To improve its photocatalytic efficiency, BiOI/CeO₂ heterojunction was designed and prepared via a facile chemical bath method. Compared to pure BiOI, the BiOI/CeO₂ heterojunction not only enhanced the absorption of visible-light but also improved the separation and transfer efficiency of photogenerated carriers. Impressively, the BiOI/CeO₂ heterojunction with a BiOI:CeO₂ molar ratio of 2:1 (named CBOI-2) exhibited the best photocatalytic performance. The CBOI-2 heterojunction can degrade 80 % of tetracycline within 60 min, and the degradation activity was almost intact after three cycles. The reaction rate constant of CBOI-2 heterojunction was 22.1 times that of BiOI and 5.8 times that of CeO₂. Moreover, CBOI-2 heterojunction behaves much better in antibacterial effect whose antibacterial efficiency reaches ∼99.6 %. A double charge-transfer mechanism was proposed in this work and it indicated that the improved photocatalytic efficiency mainly resulted from an enhanced separation and transfer of photogenerated carriers. During the photocatalytic reaction process, superoxide radicals, hydroxyl radicals and holes were generated, which play important roles in the degradation of tetracycline and antibacterial. This work provides important insights into the design of visible-light-driven photocatalysts with high photocatalytic activity for antibiotic degradation and bacteria killing.