Integrating AgFeO2 and Bi5O7I to establish an S-scheme heterojunction with significantly boosted norfloxacin photocatalytic degradation

Developing highly efficient heterojunction photocatalysts for high performance antibiotic removal is of immense importance but still remains a challenge. Herein, AgFeO2-Bi5O7I (AF-BI), a promising oxygen vacancies rich binary S-scheme heterojunction photocatalyst was synthseized via co-precipitation and hydrothermal treatment. The spherical AgFeO2 spheres were uniformly affixed on the nanorods of Bi5O7I via an intimate contact, as verified through electron microscopy. The photodegradation efficiency of optimized 15 %AgFeO2-Bi5O7I (15AF-BI) for norfloxacin (NFX) was 98.2 % (120 min) with apparent rate constant 0.022 min−1 which was 4 times pure AgFeO2. In municipal water, removal efficiency reached 90.4 % and a high 76.1 % and 65.2 % total organic carbon removal in 3 h in visible light and solar light respectively was achieved. The coupling of AgFeO2 and Bi5O7I triggers electron transfer, forming an internal electric field (leading to a directional charge transfer efficient separation of the photo-induced carriers as confirmed by PL, EIS, TPCR results. The validation of existence of S-scheme mechanism and oxygen vacancies was achieved by in-situ X-ray photoelectron spectroscopy (XPS) and EPR analysis. The free radical scavenging experiments and electron spin resonance (ESR) spectroscopy revealed ●OH and ●O2– radicals were the major reactive species involved in the photodegradation process. The heterojunction is magnetic and can be separated under guidance of magnetic field which makes reusability and separation easy. Based on ESR findings, band structure analysis and mass spectrometry NFX degradation route was predicted. This work provides effective potential solution for preparing new magnetic S-scheme heterojunctions for effective antibiotics degradation and further will expand to realm of clean energy storage and conversion.