Abstract
Electrons, photogenerated in conduction bands (CB) and trapped in electron trap defects (Tids) in titanium dioxide (TiO2), play crucial roles in characteristic reductive reactions. This review summarizes the recent progress in the research on electron transfer in photo-excited TiO2. Particularly, the reactivity of electrons accumulated in CB and trapped at Tids on TiO2 is highlighted in the reduction of molecular oxygen and molecular nitrogen, and the hydrogenation and dehalogenation of organic substrates. Finally, the prospects for developing highly active TiO2 photocatalysts are discussed.
Highlights
Since Fujishima and Honda discovered photoelectrochemical water splitting on titanium dioxide (TiO2 ) photoelectrodes in the early 1970s [1], TiO2 photocatalysis has been applied in various fields, such as the storage of solar energy [2,3,4,5], environmental purification [6], organic synthesis [7,8,9,10,11], anti-bacterial applications [12], and anti-fogging treatments [12,13]
According to the reports of Kong et al [16] and Shiraishi et al [82], the photocatalytic efficiencies increased with increasing the ratio of the amount of surface to bulk defects (Nsurface /Nbulk ) or the amount of surface to total defects (Nsurface /Ntotal )
Molecular oxygen (O2 ) in a gaseous phase would be adsorbed on the surface Tids and reduced by electrons Tids 3+ and ecb −, resulting in the efficient formation of reactive oxygen species (ROS), which oxidize benzene efficiently [16]
Summary
Since Fujishima and Honda discovered photoelectrochemical water splitting on titanium dioxide (TiO2 ) photoelectrodes in the early 1970s [1], TiO2 photocatalysis has been applied in various fields, such as the storage of solar energy [2,3,4,5], environmental purification [6], organic synthesis [7,8,9,10,11], anti-bacterial applications [12], and anti-fogging treatments [12,13] These characteristic photo-functionalities are induced by incident light, in which the behavior of photogenerated electrons and holes, as well as the roles of defects formed on surface and in lattice, are of particular importance. The prospect for developing a highly active is discussed
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