Combined modification of a TiO2 photocatalyst with two different carbon forms

Hydrothermally synthesized titanate nanotubes were carbon-doped through a thermal treatment in the presence of glucose followed by blending with single-walled carbon nanotubes (SWCNTs). A series of TiO2-based materials was prepared with various initial glucose contents and two SWCNT types, resulting in total carbon contents from 0.3 wt.% to nearly 26 wt.%. Electron microscopy observations indicated that titanate nanotubes were converted into nanorods during the thermal treatment, and X-ray diffraction patterns confirmed that all the treated materials mostly consisted of anatase TiO2. Glucose pyrolysis caused changes in the infrared and X-ray photoelectron spectra of the titania material, indicating an interaction between the inserted carbon atoms and titanium atoms. Raman spectra of SWCNT/C/TiO2 hybrids showed characteristic bands of both the SWCNT and anatase TiO2 phases. SWCNT/C/TiO2 multicomponent materials demonstrated substantially better photocatalytic activities than P25 TiO2 for methylene blue degradation under visible light irradiation. Independently from its origin, the presence of carbon caused a strong increase in the TiO2 visible light absorption. However, the results obtained with the C/TiO2 and SWCNT/C/TiO2 photocatalysts clearly showed different photocatalysis mechanisms depending on the carbon form.