Photo-Kelvin probe force microscopy for photocatalytic performance characterization of single filament of TiO2 nanofiber photocatalysts

Abstract

This is an in-depth study on the photocatalytic performance characterization for single filament of TiO₂ nanofiber photocatalysts by the novel photo-Kelvin probe force microscopy technique (photo-KPFM) and first principles calculations. Three kinds of TiO₂ nanofibers: anatase TiO₂ nanofibers (anatase TiO₂ NFs), nitrogen doped TiO₂ nanofibers (N-TiO₂ NFs), and nitrogen doped TiO₂ nanofibers decorated with platinum nanoparticles (N-TiO₂-Pt NFs) were investigated. The N-TiO₂-Pt NFs exhibit the largest negative photo surface potential shift (−182 mV) as compared to anatase TiO₂ NFs (−29 mV). The first-principles calculations based on density functional theory (CASTEP simulation software) indicate that the significant photo surface potential shift obtained by adding nitrogen and platinum into TiO₂ NFs is induced by two mechanisms: (1) enhancement in absorbance to increase exciton generation and (2) decreased charge recombination to increase surface charge. These changes in the photo surface potential of various TiO₂ nanofibers are closely correlated with their photocatalytic activity. Thus, this novel photo-KPFM provides a useful technique to easily monitor the photocatalytic capability of materials in the development of high performance photocatalysts.