Facile Vacuum Annealing-Induced Modification of TiO2 with an Enhanced Photocatalytic Performance

In this work, the photocatalytic performance enhancement of hydrothermally prepared TiO2 was achieved by facile vacuum annealing treatment. Calcination of TiO2 powder in air (CA-TiO2) maintained its white color, while gray powder was obtained when the annealing was performed under vacuum (CV-TiO2). Fourier transform infrared, total organic carbon, X-ray photoelectron spectroscopy, and electron paramagnetic resonance analyses proved that vacuum annealing transformed ethanol adsorbed on the surface of TiO2 into carbon-related species accompanied by the formation of surface oxygen vacancies (Vo). The residual carbonrelated species on the surface of CV-TiO2 favored its adsorption of organic dyes. Compared with TiO2 and CA-TiO2, CV-TiO2 exhibited an improved charge carrier separation with surface Vo as trapping sites for electrons. Vacuum annealing-induced improvement of crystallinity, enhancement of adsorption capacity, and formation of surface Vo contributed to the excellent photocatalytic activity of CV-TiO2, which was superior to that of commercial TiO2 (P25, Degussa). Obviously, vacuum annealingtriggered decomposition of ethanol played an important role in the modification of TiO2. In the presence of ethanol, vacuum annealing was also suitable for the introduction of Vo into P25. Therefore, the current work offers an easy approach for the modification of TiO2 to enhance its photocatalytic performance by facile vacuum annealing in the presence of ethanol.