Enhancement of redox capacity derived from O-doping of g-C3N4/WO3 nanosheets for the photocatalytic degradation of tetracycline under different dissolved oxygen concentration

Abstract

Element doping is an essential method for adjusting band structure, light absorbance and charge transfer, and separation of semiconductors. Besides this, whether the photocatalyst can function in an oxygen-deficient environment is also important. Herein, a novel Z-scheme heterojunction photocatalyst O-doped g-C₃N₄/WO₃ (OCN/W) was fabricated and used for the photocatalytic degradation of tetracycline (TC) at different dissolved oxygen concentrations. The introduction of O atoms into g-C₃N₄via hydrothermal treatment manipulates the band structure of the material by increasing the conduction band potential, thus producing more ˙O₂⁻. The TC removal rate of OCN/W-2.0 is 89.8% within 60 min under visible light irradiation, which is 1.77 times higher than that of porous g-C₃N₄ nanosheets (PCN). Furthermore, the photocatalytic performance of OCN/W-2.0 also reaches 75% even under oxygen-deficient conditions. The effects of different anions and humic acid in the reaction system can be neglected. The enhanced performance can be attributed to the improved charge separation and the outstanding optical properties of the Z-scheme heterojunction. A possible mechanism was postulated, in which ˙O₂⁻ and h⁺ are the main reactive species in TC degradation. The OCN/W-2.0 shows a stable structure and outstanding reusability. This work provides insight into antibiotics removal under different dissolved oxygen conditions and the design of photocatalysts for practical applications.