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The TiO 2 nanoparticles with high photocatalytic activity were prepared by the surfactant-free microemulsion (SFME)−hydrothermal method at lower temperatures using oil-in-water SFME systems as templates. The phase diagram of the SFME ethyl acetate (EA)/propan-2-ol/water was determined by electrical conductivity and UV−visible spectroscopy. The synthesized TiO 2 nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, and N 2 adsorption− desorption techniques. They were all assigned to the anatase phase and showed type IV adsorption−desorption isotherms with type H2 hysteresis loops. As the EA content (f O ) of the SFME decreases, the Brunauer−Emmett−Teller (BET) specific surface area (S BET ) of the TiO 2 nanoparticles increases. This results in an increase in the photocatalytic activity of the TiO 2 nanoparticles. With an increase in temperature, the photocatalytic activity of the TiO 2 nanoparticles increases significantly, whereas the S BET values decrease and the crystal size increases. Under the same conditions, the degradation rate of the TiO 2 prepared at 190 °C reaches 97%, which is significantly higher than that of Degussa P-25 (66%). This may be due to the use of the SFME system to synthesize the TiO 2 nanoparticles, which avoids the blocking effects of surfactant molecules on the active sites of the nanoparticles.

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