Morphology and photocatalytic performance of nano-sized TiO2 prepared by simple hydrothermal method with different pH values

pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti(SO4)2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano-sized TiO2 powder with various morphologies and sizes was synthesized. Changes in morphology, size and phase type with pH values of samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. Results show that under the present preparation conditions, TiO2 powder is an anatase phase with pH value less than 11, but is more likely to be a brookite phase with pH value more than 11. With the increase in pH value from 1 to 11 in hydrothermal environment, nano-sized anatase TiO2 gradually grows up in all directions. {001}, {101} and {100} groups of crystal plane are the exposed crystal planes of nano-sized anatase TiO2 for the (004), (101) and (200) facets found in high-resolution TEM image. The photocatalytic performance of nano-sized TiO2 with different morphologies was compared by measuring their photocatalytic degradation rates for methylene blue under ultraviolet light. Results show that anatase TiO2 prepared under the alkalescent hydrothermal environment (pH = 9, 11) has a better photocatalytic degrading performance. Different sizes and phases of nanoscaled TiO2 powders with different photocatalytic performances can be prepared by the control of pH value of hydrothermal solutions.