SPECTROSCOPIC DETERMINATION OF FLAT-BAND POTENTIALS FOR POLYCRYSTALLINE TIO2 ELECTRODES IN NONAQUEOUS SOLVENTS

The flatband potential V(fb) of a polycrystalline TiO2 electrode has been determined, using a newly developed spectroscopic technique, in a range of nonaqueous solvents (MeCN, THF, DMF, MeOH, and EtOH). It has been found that V(fb) is significantly more positive for water and nonaqueous protic solvents (MeOH and EtOH) than for nonaqueous aprotic solvents (MeCN, DMF, and THF) due to establishment of a proton adsorption-desorption equilibrium. Further, we observe that V(fb) is independent of the electrolyte used in nonaqueous protic solvents, but in nonaqueous aprotic solvents V(fb) may depend on the electrolyte cation. Cations which have been found to be potential determining are Li+, Na+, and Mg2+ Results indicating that both cation adsorption and intercalation are important in determining V(fb) are presented