Alcohol solvents evaporation-induced self-assembly synthesis of mesoporous TiO2−x−y C x N y nanoparticles toward visible-light driven photocatalytic activity

Abstract

A one-step solvent evaporation-induced self-assembly (SEISA) process was demonstrated to prepare carbon and nitrogen co-doping mesoporous TiO2 nanoparticles (MesoTiO2−x−yCxNy-S) using an ionic liquid as carbon and nitrogen sources as well as mesoporous template. After the evaporation of different solvents (methanol, ethanol, and isopropanol) and subsequent calcinations at 773 K, the obtained MesoTiO2−x−yCxNy-S samples were systematically characterized by a variety of spectroscopic and analytical techniques, including small- and large-angle X-ray diffraction (XRD), Raman, transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, Fourier transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopies. The results indicate that the solvents play an essential role on the chemical microstructure, doping elemental states, and photocatalytic performance of catalysts. The MesoTiO2−x−yCxNy-I samples have the lowest band gap of ca. 2.75 eV and strongest absorbance of visible light in the range of 400–600 nm. Among the MesoTiO2−x−yCxNy-S photocatalysts, the MesoTiO2−x−yCxNy-M catalysts show superior photocatalytic activity of hydrogen generation in methanol aqueous solution under visible light irradiation as compared to MesoTiO2−x−yCxNy-E, MesoTiO2−x−yCxNy-I, and commercial Degussa TiO2. This result could be attributed to the moderate C,N co-doping amounts on their developed mesoporous texture (pore size = 8.0 nm) and high surface area (107 m2 g−1) of TiO2 (crystallite size = 9.9 nm) in the MesoTiO2−x−yCxNy-M catalysts.