Photoelectrochemical electrolyser

Figure 2.41. Single-chip photoelectrochemical electrolyser, with electrode assembly simply immersed into the electrolyte, according to the laboratory-scale design of Yamada et al. (2003).

Figure 2.42. Two-compartment photoelectrochemical electrolyser (Milczarek et al., 2003), suggesting optimum performance for an transporting membrane area 2-3 times larger than that of the light-exposed electrode. Gas outtakes are only indicated.

Another interesting work is the recent report by Licht et al [72, 75, 94]. Although the system they studied was not a strict photoelectrochemical one, since the photovoltaic system was separated from the water electrolyser, their study is of general interest for the water oxidation field. The photovoltaic cell was connected to a water splitter catalyst system of considerably larger area than the solar cell. With this design, it was possible to combine a high solar cell efficiently with a low photocurrent density over the electrolyzer (jph = 0.44 mA/cm2), which minimized the overpotential needed for water oxidation. An overall efficiency as high as 18.3% was obtained. 

And the last remark, which is of principal character in my opinion. In terms of the proposed photoelectrochemical hypothesis of photosynthesis decomposition of v/ater is considered as a process taking place in the molecular electrolyser. Its anode and cathode areas are on the same surface of the membreine and, under these conditions, electrolysis has "asymmetric" character. 

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