Shock synthesis of N-doped titania and its photocatalytic activity under visible irradiation

Shock transformation and shock-induced chemical reaction in materials can lead to their obvious changes of physical and chemical properties. In this paper, the powder mixtures of nitrogen-rich of C₂N₄H₄ and P25 TiO₂ or metatitanic acid were shocked by the impact of flyer plates driven by explosive detonation, and the recovered samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and UV-Vis spectra and evaluated by the photocatalytic degradation of methylene blue and Rhodamine B. The results indicate that the doping level of nitrogen-doped TiO₂ reaches 8.88% (atom fraction) using the P25 TiO₂ as raw materials which exhibits obvious absorption in visible region. Its energy gap decreases to 1.75 eV together with the formation of srilankite high-pressure phase. The doping level is 3%-4% (atom fraction) corresponding to the small variation of the energy gap using the metatitanic acid as raw materials. The specific surface area of the sample increases dramatically due to the unique shock dehydration-expansion mechanism. The nitrogen-doped TiO₂ have better adsorption capability and photocatalytic activity under visible irradiation for the degradation of methylene blue and Rhodamine B, among which treated at higher impact velocity shows the higher photocatalytic activity.