Abstract
TiO2 probably plays the most important role in photocatalysis due to its excellent chemical and physical properties. However, the band gap of TiO2 corresponds to the Ultraviolet (UV) region, which is inactive under visible irradiation. At present, TiO2 has become activated in the visible light region by metal and nonmetal doping and the fabrication of composites. Recently, nano-TiO2 has attracted much attention due to its characteristics of larger specific surface area and more exposed surface active sites. nano-TiO2 has been obtained in many morphologies such as ultrathin nanosheets, nanotubes, and hollow nanospheres. This work focuses on the application of nano-TiO2 in efficient environmental photocatalysis such as hydrogen production, dye degradation, CO2 degradation, and nitrogen fixation, and discusses the methods to improve the activity of nano-TiO2 in the future.
Highlights
Fossil fuel is a non-renewable resource with limited reserves [1,2,3]
Due to its physical structure and good optical properties, titanium dioxide is considered to be a promising semiconductor photocatalyst, while nano-TiO2 has the advantages of large specific surface area and more exposed active sites, so it has better performance than TiO2
The important environmental applications of the nano-TiO2 photocatalyst were highlighted in this review such as hydrogen production, dye degradation, CO2 degradation, and nitrogen fixation
Summary
Fossil fuel is a non-renewable resource with limited reserves [1,2,3]. Over the past 140 years, we have consumed one trillion barrels of oil, and today, the world’s demand for energy has exceeded. For TiO2 , as the particle size decreases, its photocatalytic activity will increase to a certain extent, showing a specific size effect. That is, when the particle size drops to a certain value, the electron energy level near the Fermi level changes from a quasi-continuous to a discrete energy level or a widening energy gap At this time, the potential of the conduction band becomes more negative, and the potential of the valence band becomes more positive, thereby increasing the energy of photogenerated electrons and holes, enhancing the redox capability of the semiconductor photocatalyst and improving its photocatalytic activity [29,30,31]. Metal and nonmetal ions, introducing vacancy and fabricating composites with other semiconductors, the band gap of TiO2 was adjusted to make it have better photocatalytic activity [47]
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