Photoelectrolysis of water at high current density: Use of ultraviolet laser excitation

Abstract

The behavior of TiO2 and SrTiO3 photoanodes in cells for the photoelectrolysis of H2O has been investigated for high-intensity 351 364-nm excitation from an Ar ion laser. Intensities up to 380 W/cm2 have been used. For TiO2 a small amount of surface decomposition is found after irradiation at high intensity, whereas SrTiO3 undergoes no detectable changes. Current-voltage properties for both electrodes are essentially independent of light intensity up to the level of 380 W/cm2, and there is little if any change in quantum efficiency for electron flow. Photocurrent densities have been shown to exceed 5 A/cm2 for O2 evolution. Data show that the energy storage rate associated with the SrTiO3 photoelectrolysis can exceed 30 W/cm2; this represents the highest demonstrated rate of sustained optical to chemical energy conversion.