In situ co-crystallization synthesis of the direct Z-scheme Bi5O7I/Bi2SiO5 heterojunction for enhanced photocatalytic rhodamine B and ciprofloxacin degradation

Semiconductor photocatalysis has driven considerable interests for its desirable potential to tackle the worldwide energy shortage and environmental pollution. In this paper, a novel Bi5O7I/Bi2SiO5 Z-scheme heterojunction photocatalyst was in situ synthesized via a co-crystallization process and partial anion exchange strategy. The XRD and FT-IR pattern validated the successful preparation of the heterojunction. The optimal Bi5O7I/Bi2SiO5 heterojunction displayed an excellent photocatalytic activity towards the ciprofloxacin under the simulated solar light, and the rate constant (0.46021 h-1) was 2 and 7.8 times higher than that of pure BiOI (0.22967 h-1) and Bi2SiO5 (0.05877 h-1). Similarly, the degradation efficiency on rhodamine B (RhB) reached 94%, which was much higher than that of the single photocatalysis. The enhanced photocatalytic performance of the heterojunction photocatalyst could be attributed to the formation of the direct Z-scheme heterojunction between the Bi5O7I and Bi2SiO5, which was favorable for retarding the recombination of photoinduced electron-hole pairs. Moreover, the bacteriostatic activity testing illustrated the toxicity of drug solutions decreased sharply after the photocatalytic degradation with the Bi5O7I/Bi2SiO5-3. The ESR characterization analysis and the free radical trapping experiments synergistically determined the Z-scheme electron transfer path of the heterojunction. The possible photocatalytic mechanism of Bi5O7I/Bi2SiO5 heterojunction was proposed. Overall, the well-designed Bi5O7I/Bi2SiO5 heterojunction depicted great practical promise in efficient treatment of organic pollutants.