Synergistic roles of Ag+ and Ag0 in TiO2:Ag photocatalyst for enhanced solar-driven degradation of mixed dye pollutants

Abstract

The degradation of organic dyes is not only an environmental concern but also a platform for exploring charge-carrier dynamics in photocatalytic nanomaterials. Here, we investigate the impact of Y, Au, and Ag doping on the electronic and optical properties of hydrothermally synthesized TiO2 nanoparticles and their relation to solar-driven photocatalysis. Among the samples, TiO2:Ag exhibits the most pronounced activity, achieving >93 % removal of rhodamine B, methyl orange, and methylene blue in both single- and mixed-dye systems under natural sunlight (similar to 830 W/m(2)). This superior performance originates from the coexistence of Ag+ dopants and plasmonic Ag-0 species: Ag+ introduces intermediate states that narrow the bandgap and extend visible-light absorption, while metallic Ag-0 forms Schottky junctions and supports localized surface plasmon resonance, thereby enhancing charge separation and prolonging carrier lifetimes. The synergy between Ag+ and Ag-0 establishes a fundamental mechanism for efficient photocarrier generation, transport, and utilization in semiconductor photocatalysts. These findings provide physics-based insight into dopant-plasmon interactions and band-structure engineering, offering generalizable design principles for visible-light-active photocatalysis and optoelectronic applications.