High-temperature calcination and hydrogen reduction of rutile TiO2: A method to improve the photocatalytic activity for water oxidation

Rutile titania (TiO2) is an efficient photocatalyst for oxidizing water to O-2. The photocatalytic activity of particulate rutile for water oxidation was significantly improved by H-2 reduction at 700 degrees C, after calcination at 1100 degrees C. The improved activity was due to an increase in crystalline size during calcination, and an increase in conduction band electron concentration by the creation of oxygen vacancies. In contrast to the consideration that oxygen vacancy increases the recombination of electron and holes, the hydrogenated TiO2 exhibited high apparent quantum efficiency for O-2 evolution, 41% under irradiation at 365 nm. It was found that H-2 treatment improved the photocatalytic activity per unit of surface area not only for O-2 evolution but also for H-2 evolution and acetic acid decomposition. The effect of H-2 reduction treatment was obtained only if the rutile particle was previously calcined at temperatures higher than 1000 degrees C. This suggests that space charge layer in large crystalline particles is involved in the activation mechanism of hydrogenated rutile TiO2 particles. (C) 2014 Elsevier B.V. All rights reserved.