Photocatalytic and photochemical processes of AgCl/TiO₂ studied with a fully integrated X-ray photoelectron spectrometer

A fully integrated X-ray photoelectron spectrometer (XPS) was employed for the investigation of the separation processes and recombination behaviors of photogenerated electrons and holes on the surface of AgCl and ultra-small nano-titanium oxide cluster composite photocatalyst (AgCl/TiO₂). A facile route, by direct colloidal synthesis, for preparing AgCl/TiO₂ with high stability and enhanced visible light (Vis) driven catalytic activity was reported. The photocatalytic activity of AgCl/TiO₂, which revealed that the photo-degradation rate of the as-prepared AgCl/TiO₂ was nearly 10.5 times higher than that of bare AgCl, was evaluated by applying it to the photo-degradation of methyl orange (MO) in water solution. Moreover, AgCl/TiO₂ exhibited an outstanding long-term stability during ten cycles of photo-degradation. The band gap of AgCl decreased from 3.25 to 2.85 eV because of the ultra-small nano-TiO₂ clusters that were pinned to its surface. The results indicate that the band gap narrowing and surface plasmon resonance (SPR) of Ag (0) were two major contributors to the enhancement of the photocatalytic activity of AgCl/TiO₂ by improving the utilization of Vis. In situ XPS analysis was, therefore, certified as a beneficial method to explore the catalytic mechanism of photocatalysts.