Au nanoparticles decorated sulfonated graphene-TiO2 nanocomposite for sunlight driven photocatalytic degradation of recalcitrant compound

Au nanoparticles decorated with sulfonated graphene-TiO2 nanocomposites at varying Au concentrations were prepared by hydrothermal method followed by a polyol reduction process. The structural, optical and morphological properties of the prepared photocatalyst were studied using XRD, XPS, Raman, FTIR, UV-DRS, PL and HRTEM. The results reveal that with the increasing loading of Au nanoparticles the band gap of the nanocomposite decreases, and also exhibits reduction in the electron hole pair recombination rate. The results of spectroscopic and microscopic analysis confirm the presence of Au nanoparticles and sulfonated graphene in the composite photocatalyst. The photocatalytic activity of the nanocomposite was investigated by examining the removal of Methyl Orange, Rhodamine B and recalcitrant compound p-nitrophenol under sunlight irradiation. The effect of Au loading on composite shows an increase in photocatalytic activity up to threshold value of 2 mM beyond which it decreases. At this composition, Au decorated sulfonated graphene-TiO2 composites catalyst exhibit 3.2 fold higher photocatalytic performance compared to pristine TiO2 system. The improved photo catalytic performance is attributed to the synergistic effect of increased interfacial electron transfer between composite, decreased recombination rate of photoexcited electrons and holes, and the plasmonic effect of Au nanoparticles.