Polypyrrole-decorated ZnO/g-C3N4 S-scheme photocatalyst for rhodamine B dye degradation: Mechanism and antibacterial activity

Abstract

Polypyrrole (PPy) and graphitic carbon nitride (g-C3N4) nanoparticles are added to the surface of ZnO nanorods to successfully produce a Step-scheme (S-scheme) photocatalytic system known as g-C3N4/PPy/ZnO (GPZ) by a multistep process: hydrothermal and calcination processes, followed by polymerization. During the formation of the heterojunction, the oxygen vacancy (OV) on ZnO promotes effective separation and increases the redox power of the photogenerated excitons via the built-in internal electric field of S-scheme pathways between g-C3N4 and ZnO. The successful construction of the S-scheme heterojunction was substantiated through X-ray photoelectron spectroscopy, experimental calculations, radical trapping experiment, and liquid electron spin resonance (ESR) characterization, whereas the existence of OVs was well confirmed by ESR analysis. Meanwhile, the PPy served as a supporter, and the polaron and bipolaron species of PPy acted as electron and hole acceptors, respectively, which further enhances the charge-carrier transmission and separation in the ternary GPZ photocatalyst. The photocatalytic activity of the PPy-designed ternary photocatalyst g-C3N4/PPy/ZnO is outstanding and is greater than that of other samples like g-C3N4, ZnO, and ZnO/g-C3N4 and remove 99.0% of RhB (50 mg/L) in 60 min. RhB could be degraded most effectively by GPZ-0.75 photocatalysis at a pH of 7, and 1.0 g/L of the photocatalyst was the ideal concentration. Gram-positive (G + ve) and Gram-negative (G-ve) microorganisms were used as test subjects to determine the antibacterial effectiveness of the photocatalysts using the good diffusion approach. Ternary g-C3N4/PPy/ZnO heterostructure outperformed its competitors in terms of antibacterial activity. Additionally, after five cycles, the as-synthesized photocatalyst showed superb stability. By using a photocatalyst with a superior utilization efficiency of visible light energy, this paper offers a clearly promising, highly effective, and simple method to destroy exceedingly harmful and renowned contaminants.