Recent Progress in Synthesis Strategies and Photocatalysis of 3d Transition-Metal-Doped TiO2 for Wastewater Treatment

Abstract

Nanosized titanium dioxide (TiO2) is one of the most widely studied photocatalysts for environmental remediation, especially for wastewater treatment. The pristine TiO2 possesses chemical stability, low cost and high oxidative potential, but its wide bandgap and poor absorption in the visible region limit its practical application. Doping with 3d transition metals (e.g., V, Cr, Mn, Fe, Co, Ni, Cu, Zn) has become a promising approach to extend the photoresponse of TiO2, tune its electronic structure, and improve charge-separation efficiency. This review provides a comprehensive survey of synthesis routes for 3d transition-metal-doped TiO2 nanomaterials and critically discusses the influence of dopants on phase composition, crystallinity, surface characteristics, and optical properties. This review focuses on recent advances in visible-light-responsive TiO2 nanostructures (2020-present) with particular attention to their performance in degrading organic pollutants. This review summarises the design principles, structure-property relationships and environmental applications of 3d transition-metal-doped TiO2 to guide the future development of highly efficient photocatalysts for sustainable water treatment.