Review on Modified TiO₂Photocatalysis under UV/Visible Light: Selected Results and Related Mechanisms on Interfacial Charge Carrier Transfer Dynamics

TLDR

Titania is a widely used benchmark photocatalyst, yet its large band gap and rapid charge‑carrier recombination limit efficiency, prompting strategies that modify its electronic band structure or surface properties to enhance activity. This review surveys recent advances in these modification strategies and examines new physical insights into charge‑carrier generation, trapping, detrapping, and surface transfer. The authors analyze how each strategy influences charge‑carrier dynamics—generation, trapping, detrapping, and transfer to the surface—to support the derived conclusions. They report synergistic effects in mixed‑polymorph titania and theories of enhanced activity, and outline recent work on anatase with abundant reactive {001} facets and visible‑light band‑gap extension via nonmetal doping.

Abstract

Titania is one of the most widely used benchmark standard photocatalysts in the field of environmental applications. However, the large band gap of titania and massive recombination of photogenerated charge carriers limit its overall photocatalytic efficiency. The former can be overcome by modifying the electronic band structure of titania including various strategies like coupling with a narrow band gap semiconductor, metal ion/nonmetal ion doping, codoping with two or more foreign ions, surface sensitization by organic dyes or metal complexes, and noble metal deposition. The latter can be corrected by changing the surface properties of titania by fluorination or sulfation or by the addition of suitable electron acceptors besides molecular oxygen in the reaction medium. This review encompasses several advancements made in these aspects, and also some of the new physical insights related to the charge transfer events like charge carrier generation, trapping, detrapping, and their transfer to surface are discussed for each strategy of the modified titania to support the conclusions derived. The synergistic effects in the mixed polymorphs of titania and also the theories proposed for their enhanced activity are reported. A recent venture on the synthesis and applications of anatase titania with a large percentage of reactive {001} facets and their band gap extension to the visible region via nonmetal ion doping which is a current hot topic is briefly outlined.