NEW APPROACH TO A ROTATING-RING DISK ELECTRODE

The mechanism of the oxidation of water by photogenerated holes in an n-type semiconductor was elucidated by using a rotating ring disk electrode (RRDE) with n-TiO//2 as a disk. The heterogeneous electrode process was found to be hydroxyl radical (OH) formation. Hydrogen peroxides were produced in solution by the homogeneous second-order chemical reaction of hydroxyl radicals. The rate constant k//2 for OH plus OH yields **k**2 H//2O//2 was found to be 1. 5 multiplied by 10**1**1 M** minus **1 s** minus **1 (1 mol** minus **1 s** minus **1) on the basis of a model that is developed. The catalytic rate parameter of electrochemically generated radicals with redox species such as Fe**2** plus could also be determined using this model.