LaTiO₂N/Bi₂S₃ Z-scheme nano heterostructures modified by rGO with high interfacial contact for rapid photocatalytic degradation of tetracycline

Rationally fabricated Z-scheme hetero-junctions with intimate interfacial contact have proven to accelerate the photocatalytic degradation of noxious pollutants by effectively suppressing the recombination and promoting charges transfer rate. Herein, we report fabrication of reduced graphene oxide (RGO) modified LaTiO₂N/Bi₂S₃ heterojunction photocatalyst by sovothermal route. The microstructure analysis, structure determination, electronic and optical analysis of as prepared photocatalysts was done by using multiple techniques. The Z-scheme LaTiO₂N/Bi₂S₃@RGO (LBR) photocatalyst shows remarkable performance for photo-degradation of tetracycline (TC) under visible light. 96.4% TC was eliminated within 90 min under visible light with ~100% removal in 60 min under full spectrum irradiation. In addition the heterojunction shows 80.2% TC removal under natural sunlight irradiation. The TC degradation with LBR heterojunction is ~9 times faster than bare Bi₂S₃. The Z-scheme transfer follows the route as Bi₂S₃ → RGO → LaTiO₂N and provides a swift path for movement of electrons from CB of LaTiO₂N to VB of Bi₂S₃. The possible degradation route of TC has also been proposed based on quenching experiments and identification of degradation intermediates by Liquid chromatography-mass spectrometry (LC-MS). The quenching experiments reveal that [rad]O₂ ^– radicals are the main active species involved followed by [rad]OH radicals which has been explained by thermodynamic feasibility of their production from the junction arrangement. The mechanism has been explained by Z-scheme transfer by comparing to the conventional type-II junction. The enhancement in photocatalytic activity is primarily attributed to Z-scheme charge transfer between LaTiO₂N and Bi₂S₃ facilitated by reduced graphene oxide sheet via strong interfacial contact maintaining high potential for redox conversions. The recycling experiments reveal the stability and reusability of the LBR hybrid photocatalyst with ability to perform under sunlight. The novel nitrides-phosphide based junction with improved properties for visible and solar photocatalytic activity provides future prospects in forming superior hetero-structures for environmental remediation.