Visible-light-driven oxygen vacancies and Ti3+ co-doped TiO2 coatings prepared by mechanical coating and carbon reduction

The photocatalytic activity of TiO2 coatings was improved through introducing the defects including Ti3+ and oxygen vacancy by means of mechanical coating followed by carbon reduction at elevated temperatures. The samples were characterized by XRD, SEM, XPS, EPR and UV-vis absorption spectrum. The XRD results showed that the phase transformation from TiO2 to Ti4O7 occurred when temperature was raised to 1173 K holding for 0.5 h. The XPS and EPR results confirmed that the defects including Ti3+ and oxygen vacancies in the surface and bulk of TiO2 coatings. Furthermore, the concentration of the bulk defects was increased with the increase of reduction temperature or holding time. The UV-vis absorption spectra revealed that the carbon reduction greatly enhanced visible light absorption due to the introduction of Ti3+ and oxygen vacancies. A moderate relative concentration ratio of bulk and surface defects including Ti3+ and oxygen vacancies favored to improve the photocatalytic activity.