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

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.