Enriched surface oxygen vacancies of Bi2WO6/NH2-MIL-68(In) Z-scheme heterojunction with boosted visible-light photocatalytic degradation for levofloxacin: Performance, degradation pathway and mechanism insight

Abstract

Exploring effective approach to promote more comprehensive charge transfer and efficient spatial charge separation is considered to be a prospective strategy to reinforce photocatalytic degradation activity. Herein, the oxygen vacancy modified Bi2WO6/NH2-MIL-68(In) Z-scheme heterojunction photocatalyst was successfully fabricated via a facile solvothermal method. The chemical structure, morphology, and optical properties of the photocatalyst were characterized in detail. The optimized Bi2WO6/NH2-MIL-68(In) Z-scheme heterojunction displayed the maximum photocatalytic efficiency (84.3 %) for the degradation of levofloxacin (LEV), which was significantly higher than that of pure Bi2WO6 (45.1 %), oxygen vacancy modified Bi2WO6 (69.4 %), and NH2-MIL-68(In) (49.3 %). Importantly, the high-resolution mass spectrometry (HRMS), three-dimensional excitation-emission matrix (3D EEMs) fluorescence spectra, the photo-electrochemical and photo-luminescence measurement, radical trapping test, and electron spin resonance (ESR) technique were carried out to illuminate the probable degradation pathway and mechanism of the LEV. The improved photocatalytic efficiency can be ascribed to the synergetic effect between oxygen vacancy and the Z-scheme heterojunction, which can serve as trapping centers to enhance the generation of photoexcited electrons and accelerate the charge transfer. Meanwhile, the effects of pH, photocatalyst dose, LEV concentration and different kinds of harmful organic pollutants were systematically explored from the practical application. This study offers a novel perspective for the integration of defect engineering and Z-scheme heterojunction in efficient organic pollutants degradation.