Enhanced photocatalytic reduction of Cr(VI) by ZnO-TiO ₂-CNTs composites synthesized via microwave-assisted reaction

ZnO-TiO ₂-carbon nanotubes (CNTs) composites are successfully synthesized using microwave-assisted reaction of ZnO precursor in TiO ₂ and CNTs suspension using a microwave synthesis system and they are used as photocatalysts for photocatalytic reduction of Cr(VI). The results show that the CNTs addition could enhance the photocatalytic performance of ZnO-TiO ₂ composites. The ZnO-TiO ₂ composites achieve a maximum reduction rate of 90% at 240 min under UV light irradiation, much higher than those for the pure ZnO (58%) and the ZnO-TiO ₂ (69%). The improvement is ascribed to the increased light absorption intensity and range as well as the reduction of electron-hole pair recombination with the introduction of CNTs.