Fundamentals of TiO₂ Photocatalysis: Concepts, Mechanisms, and Challenges

Abstract

Photocatalysis has been widely applied in various areas, such as solar cells, water splitting, and pollutant degradation. Therefore, the photochemical mechanisms and basic principles of photocatalysis, especially TiO2 photocatalysis, have been extensively investigated by various surface science methods in the last decade, aiming to provide important information for TiO2 photocatalysis under real environmental conditions. Recent progress that provides fundamental insights into TiO2 photocatalysis at a molecular level is highlighted. Insights into the structures of TiO2 and the basic principles of TiO2 photocatalysis are discussed first, which provides the basic concepts of TiO2 photocatalysis. Following this, details of the photochemistry of three important molecules (oxygen, water, methanol) on the model TiO2 surfaces are presented, in an attempt to unravel the relationship between charge/energy transfer and bond breaking/forming in TiO2 photocatalysis. Lastly, challenges and opportunities of the mechanistic studies of TiO2 photocatalysis at the molecular level are discussed briefly, as well as possible photocatalysis models.

Tunable Photo‐Electrochemistry of Patterned TiO2/BDD Heterojunctions

“…It is worth mentioning that the band gap energy of a hydrogen‐terminated diamond surface is 5.47 eV, [ 54 ] which is larger than that (3.2 eV) of TiO 2 . [ 55 ] It is also known that the maximum energies of the valance band (VB) of BDD and TiO 2 in a TiO 2 /BDD pattern are 5.9 and 7.1 eV, respectively. [ 34 ] The barrier to bend the conduction band (CB) of a TiO 2 /BDD heterojunction is high, resulting in the diffusion of the electrons from TiO 2 to BDD.…”

Photogenerated Electron Transfer Process in Heterojunctions: In Situ Irradiation XPS

“…As the most effective photocatalytic material, TiO 2 has received widespread attention owing to its nontoxicity, chemical stability, and low cost. [ 13–18 ] A hybrid of TiO 2 and Ti 3 C 2 also has a much higher hydrogen evolution rate compared with pure TiO 2 . However, origin of Ti 3 C 2 to increase the photocatalyst activity is still vague.…”

Photocatalytic Advanced Oxidation Processes for Water Treatment: Recent Advances and Perspective

“…Therefore, it is vital to obtain deep insight into photocatalytic process: the formation, separation, relaxation, trapping, transfer, recombination and transportation of charge carriers for new development and characterization of photocatalytic materials. [69] Taking TiO 2 as an example, with useful photocatalytic performance, TiO 2 only responds in ultraviolet, which accounts for only~5% of sunlight, seriously inhibiting its practical application. Therefore, particular emphasis has been placed on the modification of TiO 2 for a wider photocatalytic response range.…”