Unraveling charge transfer pathways and mechanisms in visible-light-responsive Bi4O5I2/GO/Bi2Sn2O7 all-solid-state Z-scheme heterojunction photocatalysts for high-efficiency antibiotic degradation

An all-solid-state Z-scheme Bi4O5I2/GO/Bi2Sn2O7 (BI41/1.5GO/BS41) ternary heterojunction was constructed by hydrothermal-ultrasonic assisted aqueous precipitation-heat treatment method. Taking the degradation effect of tetracycline hydrochloride (TC-HCl) as a reference, the BI41/1.5GO/BS41 composite catalyst exhibits the best photocatalytic performance, and its photocatalytic reaction rate constant is 3.82 that of Bi2Sn2O7. When the dosage of BI41/1.5GO/BS41 was 0.8 g/L, the degradation rate of TC-HCl solution with initial concentration of 15 mg/L was 90.31 % (pH=8) under visible light irradiation for 120 min. Moreover, the BI41/1.5GO/BS41 also has excellent salt tolerance, universality and recycling stability. The free radical capture experiments and electron paramagnetic resonance (EPR) tests found that •O2 and h+ were the main active substances for photocatalytic degradation of TC-HCl. The characterization results show that the improvement of photocatalytic performance of BI41/1.5GO/BS41 is due to the successful construction of all-solid-state Z-scheme heterojunction with graphene oxide (GO) as an electron transport medium, which not only reduces the transfer resistance of photogenerated electrons but also improves the separation efficiency of photogenerated carriers. Finally, the TC-HCl solution after visible light degradation was detected by the liquid chromatography mass spectrometry (LC-MS), and the possible intermediate products and degradation pathways were speculated. This work provides a new perspective on the application of all-solid-state Z-scheme heterojunction photocatalysts to environmental remediation.