Photoelectrochemical systems, future

Photoelectrochemical experiments on the pyrite/H2S system, as well as theoretical considerations, led Tributsch et al. (2003) to the conclusion that CO2 fixation at pyrite probably could not have led to the syntheses proposed by Wachtershauser. The reaction mechanism involved in such reactions is likely to be much more complex than had previously been assumed. The Berlin group supports the objection of Schoonen et al. (1999) that, apart from other points, the electron transfer from pyrrhotine to CO2 is hindered by an activation energy which is too high. There is, thus, no lack of different opinions on the model of chemoautotrophic biogenesis hopefully future studies will shed more light on the situation ... 

Photoelectrochemical conversion from visible light to electric and/or chemical energy using dye-sensitized semiconductor or metal electrodes is a promising system for the in vitro simulation of the plant photosynthetic conversion process, which is considered one of the fundamental subjects of modern and future photoelectrochemistry. Use of chlorophylls(Chls) and related compounds such as porphyrins in photoelectric and photoelectrochemical devices also has been of growing interest because of its close relevance to the photoacts of reaction center Chls in photosynthesis. 

In the future, if the cost of the fuel cell system approaches 50/kW, the cost of the electrolyzer is also expected to approach a low number (about 125/kW). Such low capital costs for electrolyzer units, together with levelized electricity costs in the neighborhood of 0.02 to 0.03/kWh, would result in a competitive hydrogen cost. It is also estimated that for a photoelectrochemical method to compete, its cost needs to approach 0.04 to 0.05/kWh. The order-of-magnitude reductions in cost for both hydrogen processes are similar. 

Regarding production costs, it seems that a photo-electrochemical device in which all of the functions of photon absorption and water splitting are combined in the same equipment may have better potential for hydrogen production at reasonable costs. However, it is instructive to do a quick back of the envelope analysis for the acceptable cost by such a system. It is assumed that cost per peak watt for a photoelectrochemical device is the same as that for the possible future PV modules (see Table E-48 of Appendix E.) It... 

YILDIZ, A., Electrochemical and Photoelectrochemical Hydrogen Production, Utilization of Hydrogen and Future Aspects, (Conf., Akcay, Turkey, 1994), YOROM, Y. (ed.), NATO Advanced Study Institute on Hydrogen Energy System, Kluwer Academic Publishers (1995) 45-52. 

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