Biophotolysis, water

The upper limit of efficiency of the biophotolysis of water has been projected to be 3% for weU-controUed systems. This limits the capital cost of useful systems to low cost materials and designs. But the concept of water biophotolysis to afford a continuous, renewable source of hydrogen is quite attractive and may one day lead to practical hydrogen-generating systems. 

The electrons undergo the equivalent of a partial oxidation process ia a dark reaction to a positive potential of +0.4 V, and Photosystem I then raises the potential of the electrons to as high as —0.7 V. Under normal photosynthesis conditions, these electrons reduce tryphosphopyridine-nucleotide (TPN) to TPNH, which reduces carbon dioxide to organic plant material. In the biophotolysis of water, these electrons are diverted from carbon dioxide to a microbial hydrogenase for reduction of protons to hydrogen ... 

Water splitting can be accomplished via techniques such as electrolysis, photoelectrolysis, thermochemical, and biophotolysis. Electrolysis, thermochemical, and biophotolysis techniques are discussed in Chapter 2. Chapters 3-7 are dedicated to the discussion of photoelectrolysis. Chapter 8 discusses water electrolysis using energy derived from solar cells. Although each technique has its... 

Biophotolysis is the process of splitting water into hydrogen and oxygen through a series of biological activities utilizing solar radiation. The overall process can be represented as... 

Benemann, J., (1998), Process Analysis and Economics of Biophotolysis of Water, IEA-HIA Technical Report, March 1998. 

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