Jeffrey M. Bolts

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

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.

Stabilization of n‐type semiconductors to photoanodic dissolution: II–VI and III–V compound semiconductors and recent results for n‐type silicon

Semiconductor‐based photoelectrochemical cells for the conversion of light to electricity are described. Such cells consist of a semiconductor photoelectrode, a counterelectrode, and an electrolyte solution containing electroactive species. Results for cells employing certain n‐type II–VI (CdS, CdSe, CdTe) and III–V (GaP, GaAs, InP) photoelectrodes in solutions of electroactive X2−/Xn2−(X=S, Se, Te) species are reviewed. The key fact is that for a number of photoelectrode /X2−/Xn2− combinations we find that photoanodic decomposition of the semiconductor is virtually totally suppressed, allowing the sustained conversion of light to electricity. Preliminary results for n‐type Si photoelectrodes derivatized with electroactive ferrocene reagents are also outlined, and the associated photoelectrochemical activity of the surface species is compared to results for naked Si exposed to solutions of ferrocene.