Improved photocatalytic performance of anatase TiO2 synthesized through ethanol supercritical drying technique

Anatase titania (TiO 2 ) nanoparticles were synthesized via a self-developed ethanol vapor-thermal method at 240°C (T240) and 250°C (T250), i.e. at temperatures lower and higher, respectively, than the supercritical temperature (243.5°C, 7.0 MPa) of ethanol. Compared to T240, T250 exhibited a higher ratio of exposed (001) facets, oxygen vacancies, and concomitant TiO x . The specific surface area of T250 was 119.0 m 2 g −1 , smaller than that of T240 (144.2 m 2 g −1 ). During the degradation of methylene blue, T250 exhibited a high apparent rate constant ( K app ) of 14.5 × 10 −2 min −1 , which was 6.3 times larger than that for T240. Furthermore, compared to T240, T250 exhibited better performance toward degradation of phenol. Results of electron spin resonance spectroscopy and photoluminescence indicated that the photogenerated electron–hole pairs possessed higher separation efficiency for T250 than for T240. In summary, the excellent photocatalytic performance of T250 originates from the higher ratios of exposed (001) facets, oxygen vacancies or TiO x , C═O groups adsorbed at the surface of particles, and higher separation efficiency of photogenerated electron–hole pairs. By employing this self-developed vapor-thermal method, a variety of catalysts and their composites can be synthesized, which may exhibit novel morphological characteristics and properties as well as excellent photocatalytic performance.