Facile Synthesis of TiO2 with a Narrow Bandgap and Low Valence Band for Efficient Visible-Light Photocatalytic Degradation of Various Phenols

Efficient, low-cost, and easily scalable wide-spectral-responsive TiO2 photocatalysts are still extremely desired in driving photocatalytic degradation toward practical applications. In this work, a modified TiO2 with a narrow band gap and low valence band (VB) (CC-OV-TiO2) was successfully synthesized based on a facile sol–gel and low-temperature carbonization process, which can be used for the photocatalytic degradation and mineralization of a wide range of phenols. The results show that the interstitial doping of carbonates and the modification of surface oxygen vacancy (OV) defects together contribute to the formation of the VB tail states, which substantially narrow the band gap of TiO2 and widen the photoresponse range. Meanwhile, the carboxylated carbon species induce a substantial downward shift of the VB edge through coordination of the electron-withdrawing carboxyl groups, which further enhances the oxidation ability of the photogenerated holes. Accordingly, CC-OV-TiO2 with a narrow band gap and low VB exhibits superior and stable photocatalytic performance.