Preparation, characterization and applications of novel carbon and nitrogen codoped TiO2 nanoparticles from annealing TiN under CO atmosphere

Graphical abstract: Carbon and nitrogen codoped TiO2 nanoparticles were firstly fabricated by calcining TiN powder under CO atmosphere at different temperatures between 400 and 600 °C, both the improved photocatalytic activity for degradation of methylene blue and enhanced photovoltaic performance for dye sensitized solar cells were demonstrated. - Highlights: • CN-codoped TiO2 nanoparticles were prepared by calcining TiN under CO atmosphere. • More visible light response was confirmed by UV–vis DRS and photocatalytic results. • Enhanced conversion efficiency was observed for the DSSCs from CN-TiO2 photoanode. • CN-codoping played an important role to improve the photocatalytic performance. - Abstract: Carbon and nitrogen codoped titania (CN-TiO2) nanoparticles were fabricated by calcining titanium nitride (TiN) nanoparticles under carbon monoxide (CO) atmosphere at four different temperatures in a range of 400–600 °C. The as-prepared samples were characterized with X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). Enhanced light absorption in both the UV and visible light region was observed for the resulted CN-TiO2 nanoparticles in ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS). Improved photocatalytic activity toward the degradation of methylene blue by the CN-TiO2 nanoparticles was demonstrated under UV and visible light, respectively. The highest degradation rate was achieved for CN-TiO2 nanoparticles (13%) compared to N-TiO2 (10%) and the commercial P25 (5%) under visible light illumination for 40 min. Furthermore, the improved photocatalytic activity of CN-TiO2 was also confirmed by the degradation of colorless resorcinol under UV–vis light irradiation. Dye-sensitized solar cells (DSSCs) were fabricated using P25, N-TiO2 and CN-TiO2 photoanodes, respectively. The highest conversion efficiency of 3.31% was achieved by the DSSCs based on the CN-TiO2 photoanodes in comparison with the commercial P25 (1.61%) and N-TiO2 (2.44%) photoanodes. This work demonstrates that thermal treatment of TiN nanoparticles under CO atmosphere has shown to be a rapid, direct and clean approach to synthesize photocatalysts with enhanced photocatalytic and photovoltaic performance