Tandem photoelectrolysis system

While this reaction is substantially exothermic (6), it provides an intriguing approach to the production of fuels from renewable resources, as the required acids (including acetic acid, butyric acid, and a variety of other simple aliphatic carboxylic acids) can be produced in abundant yields by the enzymatic fermentation of simple sugars which are, in turn, available from the microbiological hydrolysis of cellulosic biomass materials ( ] ) These considerations have led us to suggest the concept of a "tandem" photoelectrolysis system, in which a solar photoelectrolysis device for the production of fuels via the photo-Kolbe reaction might derive its acid-rich aqueous feedstock from a biomass conversion plant for the hydrolysis and fermentation of crop wastes or other cellulosic materials (4). 

Fig. 6.1 A design for a tandem photoelectrolysis system that uses nanostmctured semiconductor films of opposite cairier type that are deposited on opposite sides of a single substrate that is covered on both sides with a continuous transparent conducting oxide film. The larger bandgap material is transparent to the lower energy radiation that is absorbed by the smaller gap film on the backside of the substrate...

A variety of other systems have been suggested and some were also tested such as cells containing an n-semiconductor anode and a p-type cathode, photoelectrolysis cells integrated with photovoltaic configurations, and tandem and cascade type of cells (Nozik and Memming, 1996). 

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