Structural functionalized TiO₂-mediated photocatalysts as dye degradation agents: A systematic review

Water contaminated with dyes severely impacts human health and the aquatic ecosystem, thus becoming a global problem. Photocatalysis is considered the most promising method for dye remediation and degradation. In this context, titanium dioxide (TiO₂) is considered an ideal photocatalyst due to its nontoxicity, biodegradability, abundance, recyclability, and improved properties. However, the application of TiO₂ for the removal of organic pollutants faces numerous challenges, including its wide band-gap, low affinity, mass transfer limits, particle aggregation, and regeneration issues. Due to its superior physical and chemical properties compared to pure TiO₂, considerable efforts have been made to modify TiO₂ with various materials. Structural modifications can be achieved in various ways, particularly through the introduction of dopants and the use of support materials. These factors are important for increasing the number of active sites and slowing the recombination rate of photogenerated electron-hole pairs. This review presents photo-assisted dye degradation and recent advances in supported and doped TiO₂ photocatalysts. Furthermore, the role of dopants and support materials and their contribution to improving the photocatalytic potential of TiO₂ were reported. The structural properties of TiO₂ and possible mechanisms of TiO₂-mediated dye degradation, as well as its future potential, are also discussed.