Enhanced visible-light photocatalytic activity of titanium dioxide doped CNT-C aerogel

Titanium dioxide is a widely used material as a photocatalyst. However, the wide bandgap and limitation of use at high concentrations of pollutants have impeded its widespread use. In this study, a novel aerogel of carbon–titanium dioxide hybrid strengthened by multi-walled carbon nanotubes was synthesized for photocatalytic degradation of organic pollutants from aqueous solutions under sunlight. TiO2 nanocrystals (about 9 nm in size) were synthesized by sol–gel method using TiCl4 as the precursor in sulfuric acid solution and the formed anatase phase was identified by XRD analysis. For characterization of the TiO2-CNT-C hybrid aerogels, various techniques like FESEM, EDS, XRD, BJH, BET, DRS and FTIR were utilized. The specific surface areas of the samples were between 410 and 480 m2 g−1. The DRS results showed a decrease in the band gap of the TiO2 hybrid aerogel (1.9 eV) relative to that of pure TiO2 (3.1 eV). To investigate the photocatalytic removal efficiency, methylene blue was used as a contaminant model. Photocatalytic experiments under Xenon lamp were performed with 20 mg photocatalyst in 100 ml of 50 ppm methylene blue solution. 6 samples (CAT-1, CAT-2, CXT, CA, TiO2, P25) were used to investigate the photocatalytic degradation activity. The highest removal efficiency was 95.50% and the kinetic studies revealed that the photocatalysts containing carbon aerogels followed the second-order kinetic model and the other samples followed the first-order kinetic model. The highest adsorption capacity was 238.756 mg g−1 and the lowest was 133.754 mg g−1. Adsorption–degradation mechanism was also speculated.