Highly efficient photocatalytic degradation of methylene blue by P2ABSA-modified TiO2 nanocomposite due to the photosensitization synergetic effect of TiO2 and P2ABSA

Abstract

To enhance the photocatalytic activity of TiO₂, poly-2-aminobenzene sulfonic acid (P2ABSA)-modified TiO₂ nanocomposites were successfully synthesized using an in situ oxidative polymerization method. The modified nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and a photocurrent test. The photocatalytic degradation of methylene blue was chosen as a model reaction to evaluate the photocatalytic activities of TiO₂ and P2ABSA/TiO₂ nanocomposites, with results indicating that P2ABSA/TiO₂ exhibited the higher activity. The apparent first-order rate constant, k_app, of P/T(2/1) was 0.0138 min⁻¹, which was six times higher than that of TiO₂ (0.0021 min⁻¹). Meanwhile, the P2ABSA/TiO₂ nanocomposites showed excellent photocatalytic stability, which was dependent on structural stability. A photocatalytic activity enhanced mechanism has been proposed, accounting for the photosensitization effect and synergetic effect of TiO₂ with P2ABSA. Mass spectroscopy analysis showed that there were two possible degradation pathways for MB, via degradation of the chromophoric group or the auxochrome group.