PHOTOELECTROCHEMICAL SEMICONDUCTOR SEPTUM (CDSE/TI AND TIO2/TI) SOLAR-CELLS IN RELATION TO HYDROGEN-PRODUCTION

Several finer details in the fabrication and working of photoelectrochemical (PEG) solar cells have been and are being mimicked from nature making PEC like the process of photosynthesis. A recent effort in this direction has been that of Tien and coworkers (1986), who have designed a semiconductor-septum PEC solar cell after the working principle of a thylakoid membrane in chloroplasts. Based on the theme of Tien et al., we have constructed semiconductor septum photoelectrochemical solar cells corresponding to configurations-GC/1M 3S//CdSe/Ti//aqueous electrolyte/GC and Pt/1M NaOH//TiO2/Ti//aqueous electrolyte/Pt. The septum photoelectrodes are CdSe painted on a Ti sheet and anodically oxidized TiO2 on titanium. This cell is similar to that originally designed by Tien and coworkers. The dark compartment contains solutions of 1M K2SO4 + 5M H2SO4, 1M Na2SO4 + 5M H2SO4 and IM(NH4)(2)SO4 + 5M H2SO4. When CdSe/Ti and TiO2/Ti (septum photoelectrodes of light compartment) were illuminated with tungsten and xenon-mercury lamps, respectively, it leads to the evolution of hydrogen at the titanium surface in the dark compartment without any externally applied voltage. The rate of hydrogen evolution has been found to be maximum under short circuit condition. Even though hydrogen production was invariably achieved, some anomalous results have been obtained. It appears that hydrogen production in the dark compartment may be due to light-assisted reaction as well as some chemical reactions taking place in the dark compartment. Further studies to optimize the conditions for solar-hydrogen production have been outlined.