Facile synthesis of g-C3N4@Sulfated titania nanocomposites with enhancement visible-light degradation of dyes and antibiotics: Mechanistic and DFT studies

Abstract

The photocatalytic efficiency of TiO₂ has been opposed by the fast recombination speed of photogenerated carriers. Here, g-C₃N₄ -modified sulfate-built-in TiO₂ quantum dots (ST-QDs) were successfully created using a simple ultrasonication-thermal procedure. g-C₃N₄-enrapped ST QDs with a 10 nm size were revealed by the characterization results. Because of the enhanced electron-hole separation, boosted oxygen vacancy, and enhanced light absorption in the straight forward z-scheme heterojunction, the CN@ST composites demonstrated excellent activity for the degradation of pollutants such as ciprofloxacin (20 ppm CIP degraded to 91.5% in 140 min); in the presence of potassium persulfate (2 mM), and indigo carmine (20 ppm IC, without oxidizing agent, and fully degraded in 50 min) under visible light energy. Quenching assays revealed that h⁺ and ^●OH were among the initial active molecular species produced on the catalyst surfaces, accompanied by an increased mineralization potential with TOC approaching 95% for both of the pollutants. On the composite, the interface interaction between C₃N₄ and sulfated TiO₂(001), besides the adsorption behavior of CIP and IC is inspected using the density functional theory (DFT). The compounds' molecular geometry was optimized, and Fukui indices were used to pinpoint their reactive sites. Additionally, the removal of photogenerated electrons that were collected on the (001) facets of the high-energy ST increases the photocatalytic activity since it produces a high separation with holes. This study sheds light on the processes and mechanisms by which CN@ST photodegrades CIP and IC and creates a new avenue for treating such contaminated wastewater with semiconductor photocatalytic oxidation technology.

Keywords: Ciprofloxacin; DFT analysis; G-C(3)N(4)@STiO(2); Indigo carmine; Mechanism; Photocatalysis.