A Dual-Sensitizer Strategy for Enhanced Photocatalysis by Coupling Perylene Tetracarboxylic Acid and Copper Phthalocyanine Tetracarboxylic Acids on TiO2

Titanium dioxide (TiO2) is a widely used photocatalyst, yet its activity is limited to ultraviolet light due to its large band gap. To extend absorption into the visible spectrum, this study developed a dual-sensitizer strategy by coupling perylene tetracarboxylic acid (PTCA) and copper phthalocyanine tetracarboxylic acid (CuPcTC) onto TiO2. Both dyes were selected for their strong visible light absorption, photostability, and efficient charge transfer properties. Hybrid photocatalysts were prepared via an ultrasonication–coprecipitation method and incorporated into coatings. Optical, morpho-structural, thermal, and electrochemical methods were used to characterize the hybrid photocatalysts, while photocatalytic performances were evaluated by UV–Vis spectroscopy, hydroxyl radical generation, and Methylene Blue degradation under simulated solar light. The dual-sensitized TiO2 composites exhibited broadened absorption across 400–750 nm, effective charge separation, and stable radical generation. Among the tested samples, the PTCA–CuPcTC hybrid (P3) demonstrated the highest activity, achieving efficient degradation of Methylene Blue with sustained performance over repeated cycles. Characterization confirmed uniform distribution of sensitizers, high crystallinity, and adequate thermal stability. These findings indicate that combining PTCA and CuPcTC provides synergistic benefits in light harvesting, charge transfer, and durability. The dual-sensitizer approach offers a promising route for visible-light-responsive photocatalysts in environmental remediation.