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

[Display omitted] •TiO2/SWCNT composites had higher photocatalytic activity than TiO2.•TiO2/SWCNT composites generated more holes than TiO2 did.•SWCNTs accelerated the transportation of OH radicals on composites’ surface to bulk solution.•SWCNTs were partially decomposed by OH radicals. 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 scavenger, was more significant than that with tert-butanol, a bulk solution OH scavenger; while that by TiO2/SWCNT composites with methanol or tert-butanol was similar, suggesting SWCNTs may accelerate the transportation of OH to the bulk solution. In addition, peroxide produced by TiO2/SWCNT composites after 5-min UV-A irradiation was 6μM, but gradually dropped to 2μM, 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.