Biogenic Nitrogen And Phosphorus Self-doped Titanium Dioxide: Synthesis, Characterization And Photocatalytic Properties

Photocatalysis is an important industrial process in wastewater treatment, heavy metal remediation, air purification, sterilization, etc. Titanium dioxide (TiO₂) is most widely used as photocatalysts for its efficiency, low cost, and chemical stability. However, the relatively large band gap of TiO₂ (3.2 eV) limits its further application. To improve the photocatalytic properties of TiO₂, anion-doping has been reported to be an effective way.Four typical kinds of crop seeds (rice, glutinous rice, soybean and sesame) are studied as nitrogen and phosphorus resources to synthesize biogenic N and P self-doped TiO₂. The samples are characterized by X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), nitrogen adsorption measurement, field-emission scanning electron microscopy (FESEM) and UV-vis spectroscopy. The results show that our TiO₂ possesses single anatase phase and nitrogen and phosphorus contained in original seeds are self-doped into the lattice. The introduction of biogenic N and P retards the phase transformation from anatase to rutile and inhibit grain growth to refine grains. Biogenic N and P self-doped TiO₂ is of macro- and meso-porous structure. The pore sizes at the nanoscale are distributed mostly between 2 nm and 40 nm, with an average pore width of 14.7 nm. The porus structure of the photocatalyst could offer more absorption and reaction sites for the photocatalytic reaction, favorable for enhancing photocatalytic performance. Besides, the doped TiO₂ exhibits a strongly enhanced absorption in the UV-vis light range and red shift of the absorption edge, implicating the highly efficient light-harvesting capacity and sensitization towards visible light. Furthermore, experiments of organic dyes degradation under Xe lamp irradiation indicate superior photocatalytic activity of biogenic N and P doped TiO₂, of which the degradation rate is 1.4³ times that of common TiO₂. This work may pave a new and facile pathway of utilizing discarded biomass to synthesize desirable element-doped metal oxides based on biomass resources.