The Quantum Yield of Photolysis of Water on TiO2 Electrodes

The quantum yield of the photo-currents in the electrochemical cell, n-TiO2/electrolyte/Pt, was measured under monochromatic illumination of TiO2 at various electrode potentials. It has been found that the quantum yield is very small (10−3) in case where no voltage was applied from outside, getting smaller with illumination intensity. The results of measurements of the quantum yield, together with those of the electrode potential of TiO2, at various conditions are explained from the energy level scheme of the semi-conductor and redox potentials in the solution. The very small efficiency of this photo-galvanic cell as a light energy converter has been attributed to the small difference between the flat-band potential of the TiO2 electrode and the reduction potential of H+.