Engineering Polyaniline Nanofibers/TiO2 for Enhanced Photocatalytic Degradation of Organic Contaminants: In-Depth Structural and Mechanistic Insights

This study presents the rational design of a visible-light-responsive TiO2/polyaniline (PANI) nanofiber heterostructure via in situ oxidative polymerization to overcome the limited visible-light absorption and rapid charge recombination of TiO2. Comprehensive characterization using XRD, FT-IR, XPS, SEM, UV–Vis DRS, and EIS confirmed the successful integration of TiO2 nanoparticles within a conductive polyaniline nanofiber network, enabling efficient interfacial charge transfer. The optimized TiO2/PANI-30 composite exhibited outstanding photocatalytic performance, achieving ~99% degradation of Basic Fuchsin dye within 40 min under visible light, significantly outperforming pristine TiO2. The enhanced activity is attributed to improved visible-light absorption, reduced bandgap energy, and suppressed electron–hole recombination, supported by optical and electrochemical analyses. Kinetic studies indicated pseudo-first-order behavior, with TiO2/PANI-30 showing the highest rate constant. Radical trapping experiments identified superoxide and hydroxyl radicals as the main active species, with •OH playing a dominant role. A direct Z-scheme charge transfer mechanism was suggested, preserving strong redox potentials and promoting reactive oxygen species generation. Additionally, the photocatalyst demonstrated excellent stability and reusability. These findings highlight the suggested potential of TiO2/PANI systems as efficient and sustainable photocatalysts for wastewater treatment.