Polypyrrole-based nanocomposites for visible-light photocatalysis: mechanistic insights,...

The persistent contamination of aquatic ecosystems by recalcitrant organic pollutants, including industrial dyes and pharmaceuticals, necessitates the development of efficient and sustainable water treatment technologies. While semiconductor photocatalysis offers a promising route for mineralization, conventional materials such as TiO₂, ZnO, and g-C₃N₄ are severely hindered by their reliance on UV light and rapid electron-hole recombination. Polypyrrole (PPy)-based nanocomposites have emerged as a transformative solution, leveraging PPy's unique conductivity and visible-light absorption to enable highly efficient, solar-driven photocatalysis. Unlike prior surveys that often focus solely on performance, this review systematically connects rational nanocomposite design with fundamental mechanistic insights and, critically, operational stability. The architecture of the catalyst - encompassing core-shell, ternary, and advanced Z-scheme heterojunction systems - constitutes a critical factor governing overall performance. Notably, optimized configurations have demonstrated degradation rates up to fivefold greater than those achieved by more basic designs. However, the literature reveals a crucial trade-off: the most kinetically rapid catalysts often suffer from poor long-term stability, posing a significant barrier to practical deployment. This review explores the intricate relationships between structure, performance, and stability, highlighting evidence-based design principles with direct relevance to the development of scalable water treatment technologies.