Preparation and photocatalytic properties of carbon/carbon-doped TiO2 double-layer hollow microspheres

A carbon/carbon-doped titanium dioxide double-layer hollow microsphere (C/TiO2 microsphere) photocatalyst was prepared by hydrolysis of thermal expendable microspheres (TEMs) and a TiO2 sol–gel process. The thickness of the TiO2 and carbon layers was controlled by the concentration of sulfuric acid used for hydrolyzing the TEMs. The photocatalytic activity of the samples was studied with rhodamine B as a target degradation product. The result showed that the photocatalytic activity was affected by the thickness of the carbon and TiO2 layers significantly. The C/TiO2 microspheres obtained with 65% H2SO4 possessed the best photocatalytic activity. Compared with pure TiO2, the visible light absorption range of the C/TiO2 microspheres was expanded to 643 nm; the specific surface area was more than five times of the pure TiO2; the response intensity of photocurrent was ten times of the pure TiO2. The degradation rate of rhodamine B caused by the photocatalysis of the C/TiO2 microspheres was 96% in 140 min, and kept 83% after three times of reuse. The C/TiO2 microspheres were easy for recycling and showed great potential in wastewater treatment.