Function ofTiO2Lattice Defects toward Photocatalytic Processes: View of Electronic Driven Force

Huanan Cui,Hong Liu,Chuan Wang,Jianying Shi

doi:10.1155/2013/364802

Abstract

Oxygen vacancies and Ti-related defects (OTDs) are the main lattice defects ofTiO2, which have great influence on its photocatalytic activity. To understand the relationship between the defects and photocatalytic activities, detailed discussions based on the electronic driven force provided by these defects are carried out during the three commonly accepted processes in photocatalytic reactions. It is found that these defects inevitably (i) influence the energy structure of the pristineTiO2as the isolate acceptor/donor level or hybrid with the original orbital, (ii) provide a disordered short-range force that confuses the charge carriers transferring to surface active sites, (iii) act not only as the surface active sites for trapping the charge carriers but also as the main chemisorption sites forO2,H2O, and organic species. These effects of the defects make them one of the key factors that determine the efficiency of heterogeneous photocatalysis. Clarifying the role of the defects will further facilitate the exploration and the construction of high-performance photocatalysts for practical applications.

Highlights

The construction of photocatalysis system provides a promising strategy to solve energy and environmental issues by converting solar energy to hydrogen/electric energy and oxidizing the organic compounds to reduce the chemical oxygen demand (COD) in the environment
Kong et al [40] found from scanning tunneling microscopy (STM) and positron annihilation lifetime spectroscopy (PALS) [41, 42] that the larger the proportion of surface defects was in the whole defects of TiO2, the higher the photocatalytic activity was
The formation of oxygen vacancies, VO󸀠󸀠 and VO󸀠, and the related Ti3+ defects are described. It provides an internal relationship between the defects, which is vital for understanding the behavior of the charge carriers in photocatalysis

Summary

Introduction

The construction of photocatalysis system provides a promising strategy to solve energy and environmental issues by converting solar energy to hydrogen/electric energy and oxidizing the organic compounds to reduce the chemical oxygen demand (COD) in the environment. Kong et al [40] found from STM and positron annihilation lifetime spectroscopy (PALS) [41, 42] that the larger the proportion of surface defects was in the whole defects of TiO2, the higher the photocatalytic activity was This competitive relationship between surface OTDs and subsurface OTDs on trapping charge carriers should be attributed to their electronic properties. Owning to the feature electronic density, OTDs can gather charge carriers and function as the absorbing sites for external species (e.g., O2, H2O, CO2, and plenty of organic substances) [43, 44] The adsorption of these species toward OTDs may occur in the form of dissociative adsorption (chemical adsorption). The findings of this work would facilitating the design and exploration of high-performance green photocatalysts in the molecule level

General Issues of Photocatalysis

Generation of OTDs in TiO2

The Function of Defects in Photocatalysis

Conclusion