Simultaneous Accomplishment of Water Reduction and Oxidation

In the vesicle suspension of Fig. 8 it was possible to isolate the centers for dihydrogen and dioxygen evolution and thus to avoid cross reactions of S+ and A- with the catalysts for H2 and 02 evolution, respectively. However, it turned out that 02 evolution gradually inhibits the H2 evolution, because oxygen evolved in the outer volume permeates across the membranes and destroys the apparatus for dihydrogen evolution located inside the vesicles. Note, that such a problem also arises for biological systems adapted to provide simultaneous evolution of H2 and Oz [275, 276], 

Thus the techniques have already been developed which allow us to introduce the catalysts for H2 and 02 evolution into appropriate places of the membrane system inside or outside vesicles, on the inner or outer surface of the membranes. However, the problem of efficient conjugation of the catalytic processes of H2 and 02 evolution with the PET across the membranes is still to be solved. 

Despite the fact that at present many important regularities of PET processes across the membranes seem to be understood at a qualitative level, this turns out to be insufficient for PET across membranes to be controlled purposefully. For this, more detailed quantitative mechanistic studies are needed. In particular, more data are needed concerning the location of the photosensitizer and electron carriers inside the membrane, dynamics and spatial limits of their diffusion in the membrane, the actual role of electron tunneling in providing electron transfer across the hydrophobic core of the membrane. 

Once this second task is solved, the next problem will be how to protect the sites for H2 evolution from poisoning with 02. Possible ways for solving this problem have been indicated in Sect. 5.3. 

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