Enhanced photocatalytic activity of TiO2/single-walled carbon nanotube (SWCNT) composites under UV-A irradiation

In this study, TiO2/single-walled carbon nanotube (SWCNT) composites synthesized by a low-temperature hydration and evaporation-drying process were investigated with respect to bacteriophage MS2 inactivation, nitrobenzene degradation, and redox species production under UV-A irradiation. The TiO2/SWCNT composites synthesized at a TiO2:SWCNT mass ratio of 50:1 showed the highest photocatalytic rate of MS2 inactivation and nitrobenzene degradation. The decrease in the degradation rate of nitrobenzene with sodium oxalate, a hole scavenger, by TiO2/SWCNT composites was less than that by TiO2, indicating more holes were generated in the composites. The decrease in the degradation rate of nitrobenzene by TiO2 with methanol, a surface and bulk solution (OH)-O-center dot scavenger, was more significant than that with tert-butanol, a bulk solution (OH)-O-center dot scavenger; while that by TiO2/SWCNT composites with methanol or tert-butanol was similar, suggesting SWCNTs may accelerate the transportation of (OH)-O-center dot to the bulk solution. In addition, peroxide produced by TiO2/SWCNT composites after 5-min UV-A irradiation was 6 mu M, but gradually dropped to 2 mu M, which was, nevertheless, about four times higher than that produced by TiO2. These findings demonstrate and explain the higher photocatalytic efficiency of TiO2/SWCNT composites than TiO2. (C) 2016 Published by Elsevier B.V.