A green method to prepare TiO2/MWCNT nanocomposites with high photocatalytic activity and insights into the effect of heat treatment on photocatalytic activity

Nanocomposites consisting of well-defined anatase TiO2 nanoparticles with an average diameter of 8 nm and multi-walled carbon nanotubes (MWCNTs) were fabricated by a facile two-step hydrothermal method using water as the main solvent, which is friendly to the environment and totally different from previous methods. The TiO2 nanoparticles were uniformly grafted on the surface of MWCNTs via intimate chemical bonds, which was beneficial for the enhancement of photocatalytic activity. The photocatalytic activities of as-prepared TiO2/MWCNT nanocomposites for degradation of rhodamine B under solar simulator illumination were investigated systemically. It was found that the photocatalytic activity of as-prepared TiO2/MWCNT nanocomposites was 7 times higher than that of pure TiO2 prepared via the same hydrothermal procedure. The enhancement was mainly due to the existence of MWCNTs, which could not only greatly improve the adsorption of rhodamine B, but also retard the recombination of photogenerated electron–hole pairs and absorb more light. The photocatalytic performance was further enhanced after being annealed at 400 °C and 500 °C for 1 h because of the improved crystallinity of anatase TiO2. Interestingly, the photocatalytic activities of samples annealed at 400 °C and 500 °C showed no difference, which was different from previous reports.