Phase Engineering and Modification of TiO2 Nanocrystals for Applications in Photocatalysis
CAO W. 1
1 University of Science and Technology Beijing, Beijing, China
TiO2 is widely considered the star photocatalyst among various options due to its chemical stability, nontoxicity, and low cost. In recent years, many applications in environmental purification have been developed based on TiO2 nanocrystals. TiO2 nanocrystals are typically prepared by wet-chemical methods via the condensation reaction of [Ti(OH)h(H2O)6-h]4-h (where h is the hydrolysis ratio). We demonstrated that this ratio (h) is a key factor that affects the crystal structures of TiO2. Based on the thermodynamic parameters of possible condensation reactions, the relationship between the hydrolysis ratio h and the crystal structure has been mapped and verified by experimental data. Based on this, we synthesized colloidal Cu-doped TiO2 (Cu-TiO2) nanocrystals using a facile sol-hydrothermal method. It has been found that the doping of Cu induced grain size reduction and bandgap narrowing of TiO2 nanocrystals, as well as the formation of abundant oxygen vacancies in the TiO2 nanocrystal. This resulted in improved performance for photocatalytic degradation of benzene and a high antibacterial rate of over 99.99% against both Escherichia coli and Staphylococcus aureus under visible light. Moreover, we successfully synthesized the Cu–TiO2/CuS p-n heterojunction using an in-situ sulfidation method. This structure exhibited excellent photocatalytic performance for NO removal, with a maximum removal efficiency of 85%, due to enhanced optical absorption and highly efficient charge carrier separation.