9 Semi-artificial photosynthetic Z-scheme for hydrogen production from water

Abstract

Water will be the coal of the future" stated Jules Verne in 1874 [1] and this idea is nowadays becoming reality.Faced with the increasing energy demand of mankind and the exhaustion of conventional fossil energy sources, it becomes necessary to consider future fuel alternatives. One basic and promising approach is using hydrogen as an energy carrier, provided that it is produced in an ecological and regenerative process at a scale necessary to satisfy global energy demand.Jules Verne's statement was aiming at the overall technical approach of electrical hydrolysis of water; but his statement can also be re-interpreted by thinking about nature-inspired energy conversion scheme s. One natural process which fits perfectly into this line of thought is photosynthesis.Photosynthesis is the most fundamental process for life on earth. Water is used as an electron source in the conversion of light energy into electrical and finally chemical energy. The coupling of proton reduction (2 H + to H 2 ) with the light energy conversion and the water consumption process of photosynthesis promises a bio-inspired approach that only requires free and easily available solar energy and water. The steps towards the artificial combination of individual photosynthetic key processes and proton-to-hydrogen conversion are outlined in detail in this chapter. Nature-inspired approaches for hydrogen productionGenerally, there are three principal approaches to utilize solar energy sources for the production of hydrogen: Biological approach: The natural photosynthetic energy pathway is re-routed for photobiological proton reduction in vivo. Artificial approach: Coupling synthetic molecules for light triggered water splitting and proton reduction. Semi-artificial approach: Integration and combination of isolated photosynthetic proteins in photoelectrochemical cells.The background for producing biohydrogen in the biological approach has already been specified and discussed in Biomass to Biofuels: Strategies for Global Industries [2] and is not repeated in this chapter. The strategy of artificial systems is also not considered here, for details see [3,4].

Cyanobacterial Hydrogenases and Hydrogen Metabolism Revisited: Recent Progress and Future Prospects

“…As such, production of hydrogen from water utilizing solar energy is regarded as a far more environmentally benign process compared to related chemical processes. Such is the interest displayed in using these enzymes that several attempts have been made to understand, tune the catalytic bias, and develop their synthetic homologs [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”