Solar photoanodes, surface

The Correlation Between Surface Morphology and Solar Cell Performance of WSe2 and MoSe 2 Photoanodes... 

Photoelectrochemical splitting was discussed extensively in Chapter 10. The key point is the use of trace electrocatalysts added to the surface of both photocathode and photoanode to the appropriate extent (Kainthla, Zelenay, and Bockris, 1987 Turner, 1998). If the electrolyzer is to be entirely solar driven, both electrodes must be irradiated. It is difficult to find photoanodes with the appropriate properties. Most of them dissolve electrochemically ifused as anodes for02 evolution. This can, however, be prevented by using transparent films of nonreactive oxides (Bockris and Uosaki, 1977). 

Lenzmann F., Krueger J., Burnside S., Brooks K., Gratzel M., Gal D., Ruehle S. and Cahen D. (2001), Surface photovoltage spectroscopy of dye-sensitized solar cells with Ti02, Nb205, and SrTiOs nanocrystalline photoanodes indication for electron injection from higher excited dye states , J. Phys. Chem. B 105, 6347-6352. 

In Japan, a photoelectrochemical system for outdoor operation, i.e., solar, has been constructed. Photoanodes were Ti plates with a I fim thick Ti02 surface layer with a total area of 0.17 m, cathodes were of Pt, and the electrolyte was KCl. The result was an output of 1.1 1 of hydrogen per day, the conversion efficiency was about 0.4 % which is considered relatively high compared with the small absorption wavelength range (3 % of the entire solar spectrum) by Ti02 [25]. In a more recent effort using a multi-band gap PEC cell structure, an efficiency of 12.4 % has been achieved [3]. 

To conclude, the potentiostatic anodization of metallic tungsten in an appropriate electrolytic composition provides a simple wet electrochemical tool [80] to produce highly efficient WO3 photoanodes, which, combining spectral sensitivity, highly electrochemically active surface, and improved charge transfer kinetics outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by sol gel methods and are, at the very minimum, comparable to substrates produced with vacuum technologies (i.e., RF sputtering) recently reported in the literature. 

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