Self-assembled ionic liquid synthesis of nitrogen-doped mesoporous TiO₂ for visible-light-responsive hydrogen production

Nitrogen-doped mesoporous TiO₂ has been synthesized by a simple solvent evaporation-induced self-assembly method using a nitrogen-containing ionic liquid concurrently as a nitrogen source and mesoporous template. After being evaporated and subsequently calcined at various temperatures (300–900 °C), the synthesized samples were thoroughly characterized by X-ray diffraction (XRD), Raman, small-angle X-ray scattering patterns (SAXS), N₂ adsorption-desorption isotherms, X-ray photoelectron (XPS) and UV–Vis diffuse reflectance (UV–Vis DR) spectroscopies. The obtained results suggest that the calcination temperature greatly influences the crystallization of TiO₂, formation of mesoporous structure, specific surface area and N-doping amounts. Among the fabricated photocatalysts, the samples calcined at 600 °C exhibit superior photocatalytic performance for hydrogen production in water/methanol solution under visible light illumination if compared to other synthesized samples and commercial TiO₂ (Degussa P25). The finding is possibly due to the synergy of more N-doping amounts on the well-defined mesoporous TiO₂ with highly anatase crystal phase and moderate surface area in the catalysts.