Reorientation kinetics of hydroxyl groups in anatase TiO2

The reorientation kinetics of hydrogen in a variety of complexes in the anatase polymorph of TiO2 was investigated by means of stress-induced dichroism. For the hydrogen-defect resulting in an O-H vibrational mode with a frequency of 3389 cm(-1), the energy barrier separating adjacent equivalent in-plane sites of hydrogen was determined to be independent of the isotope and equal to 0.74 +/- 0.02 eV, whereas the attempt frequency was found to be (1.10 +/- 0.20) x 10(12) and (0.75 +/- 0.15) x 10(12) s(-1) for hydrogen and deuterium, respectively. The defect with vibrational modes at 3412 and 3417 cm(-1) previously assigned to isolated hydrogen did not reveal alignment under the stress up to room temperature, which indicates that the barrier of hydrogen motion is above 0.9 eV. Published by AIP Publishing.