Synthesis, characterization, and application of polypyrrole/TiO2 composites in photocatalytic processes: A review

Abstract

Hybrid materials composed of semiconductor oxide metals and conducting polymers have been highlighted as a new class of materials, with superior properties compared to their pure constituents. Among the studied composites to photocatalytic applications, the hybrids of titanium dioxide (TiO2) and polypyrrole (PPy) are promising due to several advantages over the pure TiO2 nanoparticles. The PPy/TiO2 composite has been effectively synthetized by chemical polymerization methods as in situ polymerization, photopolymerization, electrochemical polymerization, and molecular imprinting polymerization (MIP). All the cited methods appear to be effective in reducing the band gap energy, which suggests an increase in the formation of photoexcited electron-hole pairs and, consequently, an improvement of the light absorption in the visible region (400–700 nm). In addition, the doping of PPy/TiO2 with noble metals improves the separation of charges in the semiconductor particle, inhibiting the recombination of photogenerated electron-hole pairs. All advantages are evidenced by the characterization results of SEM, TEM, HRTEM, UV-vis DRS, FTIR, XRD, PL, TGA and electrical properties. Finally, results from literature present that PPy/TiO2 composites have better photocatalytic activity than the pure TiO2, being an alternative photocatalyst promising for visible light applications. Thus, this work presents a review of the synthesis, characterization, and application of PPy/TiO2 composites in the photocatalytic processes.