**2. TiO2-based photocatalysts**

In this section, strategies on the modulation of energy band structures or surface states of wideband-gap photocatalysts, especially for TiO2, are reviewed. Currently, many strategies have been developed to modulate the band structures of TiO2, including doping, coupling with graphene, precipitating with metal particles, crystal growth design, and heterostructuring, which will be discussed.
