Effective degradation of doxycycline hydrochloride in simulated and real water by S-scheme heterojunction 2D/1D Bi4O5I2/In2O3 under visible light: DFT calculation, mechanism, degradation pathway and toxicity analysis

To effectively enhance the response to visible light, suppress the recombination of electron-hole pairs and enhance the degradation performance towards organic pollutants in water, a novel S-scheme heterojunction Bi4O5I2/In2O3 was synthesized by in situ solvothermal loading of Bi4O5I2 on the surface of In2O3, and employed to investigate its photocatalytic performance towards doxycycline hydrochloride. The prepared optimal photocatalyst Bi4O5I2/In2O3 shows excellent photo-degradation capability under visible light (94.1 %). The transfer pathway of photogenerated carriers in the Bi4O5I2/In2O3 heterojunction follows the S-scheme process, demonstrated by various characterizations and Density Functional Theory calculation. The internal electric field formed inside the Bi4O5I2/In2O3 S-scheme heterojunction impels the direct transmission of photogenerated carriers from the CB of In2O3 to the VB of Bi4O5I2, which produces the accumulation of e- and h+ on the CB of Bi4O5I2 and VB of In2O3, severally. Meanwhile, the formed internal electric field reduces the recombination rate of e-/h+. Superoxide and hydroxyl radicals contribute a major role. Degradation pathway was explored and toxicity evaluation of intermediates was also performed. The present results demonstrate that the construction of the Bi4O5I2/ In2O3 heterojunction can be a feasible route to effectively degrade antibiotic under visible light irradiation.