Promoting the oxidative removal rate of 4-chlorophenol on gold-doped TiO2/graphene photocatalysts under UV light irradiation

4-Chlorophenol photooxidation catalysed by nanosized TiO2, Au/TiO2, and matching composite materials with reduced graphene oxide (GR) has been studied upon irradiation with UV light. XPS and TEM methods have been applied to characterise prepared photocatalysts. The average size of the titania nanoparticles prepared by the sol-gel method was 20 nm. TiO2 and Au/TiO2 particles were randomly distributed on the surface of the graphene nanosheets. The average size of the Au nanoparticles in the modified titania photocatalysts was about 7 nm. XPS measurements confirmed partial thermal reduction or photoreduction of the graphene oxide to graphene. Rate constants of 4-chlorophenol photooxidation catalysed by the studied samples followed the order: Au/TiO2/GR > Au/TiO2 > TiO2/GR > TiO2. The rate constant of 4-chlorophenol degradation catalysed by an Au/TiO2/GR composite was approximately 3.9 times higher than that registered with titania. Enhanced activities of Au/TiO2/GR, Au/TiO2, and TiO2/GR photocatalysts were due to efficient charge carrier separation of the light-generated electron-hole pairs in titania semiconductor. This favoured an additional generation of HO center dot radicals on the titania valence band.