Synthesis of Carbon Nanotube-Supported Mn-TiO2 as a Photocatalyst under Visible Light

Background: TiO2 photocatalyst is promising for wastewater treatment, but it is still restricted under visible light. Objective: To prepare TiO2 based-photocatalyst of good performance under visible light. Methods: By doping manganese (Mn) and using multi-walled carbon nanotubes (MWCNTs) as a substrate, we prepared carbon nanotube-supported Mn-TiO2 (Mn-TiO2/MWCNTs) nano-composites with a solvothermal-annealing method. The samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The photocatalytic activity of Mn-TiO2/MWCNTs was investigated by the degradation of methylene blue (MB) under visible light. Results: It was found that Mn-TiO2 nanoparticles were loaded uniformly on the MWCNTs. Mn-TiO2/MWCNTs showed higher photocatalytic efficiency than pure TiO2 and Mn-TiO2. Only 47.0% of MB was degraded by TiO2 and 67.2% of MB was degraded by Mn-TiO2, while 80.0% of MB was degraded by Mn-TiO2/MWCNTs in 80 minutes. Conclusion: Because the Mn doping reduced the energy gap of TiO2 and inhibited the recombination of photogenerated electron-hole pairs and because the large suface area and good electro-conductivity of MWCNTs enhanced the photocatalytic efficiency of TiO2, Mn- TiO2/MWCNTs showed an enhanced catalytic performance under visible light.