Clay-supported anisotropic Au-modified N,S-doped TiO2 nanoparticles for enhanced photocatalytic dye degradation and esterification reactions

Abstract

Visible light active photocatalysts are very important in environmental sustainability. A clay-supported anisotropic Au nanoparticle-deposited N,S-doped TiO₂ plasmonic photocatalyst has been developed. Successful deposition of ∼10 nm of TiO₂ nanoparticles was carried out using the sol–gel method, followed by deposition of ∼40 nm Au NPs by oxalic acid reduction, on kaolinite clay. The role of Au NPs was to generate more excitons by the photocatalyst in their vicinity; the photocatalytic degradation rate constant increased by 82% in their presence. The photocatalyst was further modified by co-doping with N and S to reduce the band-gap and make it more efficient in visible light. A 9-fold increase in the degradation rate constant was observed for doped samples. The degradation rate constant further increased by 28% in the presence of an electrolyte (Na₂HPO₄) because of the enhancement of dye adsorption capacity on the clay surface. The photocatalytic esterification of oleic acid to methyl oleate increased 10-fold compared to that using an un-doped catalyst.