Surface Enhanced Raman Spectroscopic Studies on Surface Plasmon Resonance Catalytic Activity of TiO₂-Metal Nanocomposites

The rapid recombination of carriers on plasmon metal nanoparticles leads to relatively low efficiency of traditional photocatalysts. The combination of a metal and a semiconductor allows to the separation of hot electrons and holes to improve photocatalytic efficiency. In this study, Au nanoparticles were integrated with semiconductor TiO 2 nanoparticles of different sizes to improve the photocatalytic activity. Various techniques have been developed to study the mechanism of catalytic activity, the significance of band bending in the space-charge region within metal–semiconductor nanocomposites, and the built-in electric field. The results provide theoretical and experimental evidence for the design of a high-performance surface plasmon resonance (SPR) photocatalyst. To reveal the interface band structure, surface-enhanced Raman spectroscopy (SERS) was employed to analyze the band structure of the TiO 2 –metal composites. This approach was based on the electrochemical Stark effect and a molecular probe strategy, combined with X-ray photoelectron spectroscopy (XPS), Electrochemical impedance spectroscopy (EIS), and other techniques at the molecular level. The results demonstrated that charge transfer occurred spontaneously between the Au nanoparticles and TiO 2 , and that the TiO 2 –metal interface constitutes a Schottky barrier. Moreover, the size of the TiO 2 nanoparticles affects the degree of band bending. Optimal state matching was achieved with TiO 2 (60 nm)–Au, improving the photocatalytic activity of the nanocomposite. The photocatalytic coupling reaction of p-aminothiophenol (PATP) acted as a probe to study the catalytic performance of TiO 2 –metal nanocomposites. The results revealed that the introduction of TiO 2 improves the SPR catalytic activity of Au, mainly through the efficient separation of electrons and holes at the TiO 2 –metal interface.