An experimental work is presented in which alkaline solutions of glycerol are electrochemically treated at TiO2 electrodes obtained by electrochemical oxidation of Ti foils annealed a 400 A degrees C and 600 A degrees C. The semiconductor properties of the material, strictly correlated to the presence of structural defects, and their different concentration and distribution originated by the different annealing temperature are investigated. In order to derive useful indications for possible application on reduction or photo-oxidation of glycerol, particular attention is paid on the working mechanism of the electrodes in a wide range of potential at which the semiconductor may be under accumulation or depletion regime.