Impact of quenching process on the surface defect of titanium dioxide for hydrogen production from photocatalytic decomposition of water

Nanocrystalline titania was prepared by solvothermal reaction of titanium butoxide in toluene at 300 °C for 2 h. Thus obtained-powder was calcined at 300 °C in box furnace for 1 h and then quenched in various media at different temperature. The physiochemical properties of samples were investigated by using X-ray diffraction (XRD), nitrogen adsorption, CO2-Temperature Programmed Desorption (CO2-TPD), UV–visible scanning spectrophotometer, Transmission electron microscopy (TEM) and electron spin resonance spectroscopy (ESR) techniques. All physical properties such as phase, BET surface area and crystal size were not changed after quenching processes. While the CO2-TPD and ESR results indicate the changing of Ti3+ contents on the surface of TiO2 after quenching process. The amounts of Ti3+ increased as the quenching temperature decreased. Photocatalytic decomposition of water was carried out to evaluate the catalytic activity of quenched TiO2. The activity of quenched-powder increased corresponding to the increasing of Ti3+ contents increased by following order: air at 77 K > air at RT > air at 373 K > 30 wt% H2O2 at RT = 30 wt% H2O2 at 373 K > H2O at RT > H2O at 373 K.