Advancements in TiO₂-based photocatalysis for environmental remediation: Strategies for enhancing visible-light-driven activity

Researchers have focused on efficient techniques for degrading hazardous organic pollutants due to their negative impacts on ecological systems, necessitating immediate remediation. Specifically, TiO₂-based photocatalysts, a wide-bandgap semiconductor material, have been extensively studied for their application in environmental remediation. However, the extensive band gap energy and speedy reattachment of electron (e⁻) and hole (h⁺) pairs in bare TiO₂ are considered major disadvantages for photocatalysis. This review extensively focuses on the combination of semiconducting photocatalysts for commercial outcomes to develop efficient heterojunctions with high photocatalytic activity by minimizing the e⁻/h⁺ recombination rate. The improved activity of these heterojunctions is due to their greater surface area, rich active sites, narrow band gap, and high light-harvesting tendency. In this context, strategies for increasing visible light activity, including doping with metals and non-metals, surface modifications, morphology control, composite formation, heterojunction formation, bandgap engineering, surface plasmon resonance, and optimizing reaction conditions are discussed. Furthermore, this review critically assesses the latest developments in TiO₂ photocatalysts for the efficient decomposition of various organic contaminants from wastewater, such as pharmaceutical waste, dyes, pesticides, aromatic hydrocarbons, and halo compounds. This review implies that doping is an effective, economical, and simple process for TiO₂ nanostructures and that a heterogeneous photocatalytic mechanism is an eco-friendly substitute for the removal of various pollutants. This review provides valuable insights for researchers involved in the development of efficient photocatalysts for environmental remediation.