Polyaniline/Tio2 Nanocomposites: Fundamentals, Synthesis Approaches, and Applications in Photodegradation and Corrosion Resistance

Abstract

Polyaniline (Pani)/TiO2 nanocomposites have emerged as an important class of multifunctional materials owing to the synergistic integration of the electrical conductivity and redox activity of Pani with the excellent photocatalytic, chemical stability, and corrosion-resistant properties of TiO2. Although numerous studies have reported enhanced functional properties of Pani/TiO2 nanocomposites, a comprehensive understanding of the synthesis, structure and property relationships governing their multifunctional performance needs to be investigated.This review critically examines the current progress in the design, synthesis, and applications of Pani/TiO2 nanocomposites, with emphasis on the relationships between synthesis strategy, microstructure, and functional performance. The major fabrication approaches, including in situ oxidative polymerization, sol–gel processing, hydrothermal/solvothermal synthesis, electrochemical deposition, physical blending, and immobilized film techniques, are comparatively discussed in terms of their advantages, limitations, and resulting morphologies. Special emphasis is placed on correlating composition, crystallinity, particle size, interfacial interactions, surface chemistry, and morphology with the resulting optical, electrical, electrochemical, and photocatalytic properties. The review establishes that enhanced performance primarily originates from strong interfacial coupling, efficient charge separation, optimized composition, and hierarchical nanostructures, which collectively improve visible-light harvesting, charge transport, and electrochemical stability. Recent advances in ternary and heterostructured systems incorporating metal oxides, noble metals, and MXenes are also summarized, highlighting their role in promoting heterojunction formation and suppressing charge recombination. Particular attention is given to photocatalytic degradation of organic pollutants and corrosion protection, where Pani functions as a visible-light sensitizer and redox mediator, while TiO2 provides catalytic activity and an effective barrier against corrosive species. Despite considerable progress, challenges remain in understanding interfacial charge-transfer mechanisms, improving long-term durability, standardizing performance evaluation, and developing scalable, environmentally sustainable synthesis routes. The insights presented in this review provide guidance for the rational design of next-generation Pani/TiO2-based multifunctional materials for environmental remediation, protective coatings, and other advanced technological applications.