Fabrication of polypyrrole-sensitized Ag3PO4/g-C3N4 Z-scheme heterojunction for photocatalytic and antibacterial activity

Abstract

Charge segregation is crucial for improving photocatalytic activity, and visible light-assisted photocatalysis is an intriguing perspective in the detoxification of environmental contaminants. In this study, a novel Z-scheme polypyrrole sensitized 2D-g-C₃N₄/Ag₃PO₄ n–n heterojunction was fabricated by hydrothermal and in situ chemical oxidative polymerization processes at an ambient temperature. The Ag₃PO₄/PPy/g-C₃N₄ nanocomposite exhibited superior effectiveness for the degradation of TCH under visible light irradiation (λ ≥ 420 nm) and displayed 95% degradation in 45 min with a rate constant equal to 0.0782 min⁻¹. The photocatalytic activity of Ag₃PO₄/PPy/g-C₃N₄ under visible light irradiation was almost 4.5, 3.2, and 1.5 times as high as those of pure Ag₃PO₄ and g-C₃N₄ and binary nanocomposite g-C₃N₄/Ag₃PO₄, respectively. In addition, the catalytic activity of the nanocomposite in the reduction of 4-nitrophenol using NaBH₄ as a reducing agent was evaluated. The results showed that Ag₃PO₄/PPy/g-C₃N₄ exhibited the best performance in the reduction of 4-nitrophenol (4-NP) and revealed 100% conversion into the corresponding amino derivatives in 5 min with a rate constant equal to 0.0127 min⁻¹. The catalysts also demonstrate excellent antibacterial activity against both Gram +ve and Gram −ve bacteria. The PPy present in the composite acts as an electron acceptor and donor due to its π–π conjugation, which accelerates the rate of electron transfer between Ag₃PO₄ and g-C₃N₄ and enhances the segregation of electron–hole pairs, and results in the marvelous photocatalytic activity of Ag₃PO₄/PPy/g-C₃N₄. Moreover, the catalyst shows excellent stability even after the use of five consecutive cycles and retained 90% activity without any alteration in its physical appearance.