Optical and Electrochemical Study on the Performance of Au@TiO2 core-shell Heterostructured Nanoparticles as Photocatalyst for Photodegradation of Methylene Blue under Solar-light Irradiation

Abstract

The efficacy of Au@TiO2 core-shell heterostructured nanoparticles for photodegradation of methylene blue (MB) under solar-light irradiation was investigated in this study. The hydrothermal approach was used to make Au@TiO2 core-shell nanoparticles. According to structural studies utilizing SEM, TEM, and XRD analysis, the Au@TiO2 core-shell nanostructures were successfully produced. The optical band gap values of TiO2 and Au@TiO2 core–shell nanoparticles were 3.15 and 2.66 eV, respectively, indicating that the optical band gap value of Au@TiO2 toward TiO2 was decreased due to Au incorporation and the presence of a defect-induced narrowed band gap in Au@TiO2 such as Ti3+ formation and/or oxygen vacancies. Electrochemical investigations revealed that charge transfer resistance and recombination kinetics in Au@TiO2 were reduced. Under solar-light irradiation, TiO2 and Au@TiO2 core-shell nanoparticles removed 90% of 100ml of 50mg/l MB solution in 85 and 60 minutes, respectively, whereas the entire removal took 120 and 95 minutes, respectively. According to a comparison of the photocatalytic activities of Au@TiO2 core-shell nanoparticles with other reported photocatalysts for MB degradation, the fast degradation rate of Au nanoparticles was related to the SPR absorption characteristics of the Au nanoparticles, which can act as a sensitizer to increase visible light absorption. Furthermore, the results demonstrated that the proposed photocatalyst was effective in degrading MB in an actual sample of paint and pigment industrial effluent.