Title : Facile design of silver-modified BiOI/TiO₂ nanotube nanocomposites with enhanced charge separation and photocatalytic activity
Abstract:
Water pollution by persistent organic dyes poses a major environmental and health challenge, particularly due to the inefficiency of conventional treatment methods in degrading these stable compounds. Semiconductor-based photocatalysis offers a green and sustainable alternative by leveraging solar energy to generate reactive species for contaminant degradation. However, traditional photocatalysts such as TiO₂ are limited by their wide band gap (~3.2 eV), which restricts activation to the UV region, representing only a small fraction of the solar spectrum. To address this limitation, we developed a novel ternary Ag/BiOI/TiO₂ nanotube photocatalyst that synergistically combines visible-light harvesting, enhanced charge separation, and efficient interfacial electron transport within a single nanostructured architecture.
The fabrication involved a three-step process: electrochemical anodization of Ti foil to produce vertically aligned TiO₂ nanotubes, deposition of BiOI nanosheets using the Successive Ionic Layer Adsorption and Reaction (SILAR) technique, and surface decoration with Ag nanoparticles via electroless deposition. Structural and compositional analyses using SEM, XRD, FTIR, and XPS confirmed the successful formation of the composite, while UV–Vis diffuse reflectance spectroscopy revealed enhanced absorption across the visible-light region. The nanostructure₂ photocatalyst achieved a remarkable 99.12% degradation of methylene blue within 180 minutes under visible-light irradiation, substantially outperforming both pristine TiO₂ nanotubes and BiOI/TiO₂ binary systems.
Photoelectrochemical measurements demonstrated a significantly higher photocurrent response and reduced charge transfer resistance, indicative of improved photogenerated charge separation and transport. The enhanced performance is attributed to multiple synergistic effects: the surface plasmon resonance (SPR) of Ag nanoparticles amplifies visible-light absorption and injects energetic electrons into adjacent semiconductors; BiOI acts as a visible-light-active sensitizer forming heterojunctions with TiO₂; and Ag additionally functions as an electron sink, forming Schottky barriers that suppress charge recombination. The one-dimensional TiO₂ nanotube scaffold further promotes vectorial charge migration and increases surface area for photocatalytic reactions.
This work reports the integration of Ag nanoparticles and BiOI nanosheets onto TiO₂ nanotube arrays within a unified hierarchical structure. The ternary nanostructure system offers a promising platform for efficient, visible-light-driven degradation of organic pollutants, contributing to the advancement of photocatalytic technologies for water purification.
