Photocatalytic activity of nitrogen-doped TiO2-based nanowires: a photo-assisted Kelvin probe force microscopy study

In this study, a set of nitrogen-doped TiO2- based nanomaterials demonstrating photocatalytic activity was developed by combining the efforts of lattice doping and metal nanoparticle decoration and tested for photo-degradation of methylene blue dye by applying solar simulator irradiation. The surface potential shifts of these TiO2-based photocatalytic nanomaterials measured by Kelvin probe force micro- scope have been used to study the degree of electron generation of the photocatalysts after irradiation and were well correlated with the photocatalytic activity. The nitrogen-doped TiO2 nanowires decorated with Pt nanoparticles can induce obvious electron accumula- tion and result in a large shift of surface potential. The analysis shows a clear correlation between the surface potential shift and the photodegradation activity. Furthermore, a thorough comparative photocatalytic activity study combined with X-ray photoelectron spectroscopy analysis of the materials—doped with nitrogen under various conditions—reveals that the photocatalytic efficiency of the catalysts is maintained even if the lattice doping is leached e.g., by thermal treatments after doping.