Water splitting
[3][4] Since the active site of the OEC contains manganese, much research has aimed at synthetic Mn compounds as catalysts for water oxidation.
[5] In biological hydrogen production, the electrons produced by the photosystem are shunted not to a chemical synthesis apparatus but to hydrogenases, resulting in formation of H2.
Again, water is broken down into hydrogen and oxygen by electrolysis, but the electrical energy is obtained by a photoelectrochemical cell (PEC) process.
[11] The conversion of solar energy into hydrogen by means of water splitting process might be more efficient if it is assisted by photocatalysts suspended in water rather than a photovoltaic or an electrolytic system, so that the reaction takes place in one step.
In the Mponeng gold mine, South Africa, researchers found in a naturally high radiation zone a community dominated by Desulforudis audaxviator, a new phylotype of Desulfotomaculum, feeding on primarily radiolytically produced H2.
[15] The high temperature requirements and material constraints have limited the applications of the thermal decomposition approach.
Other research includes thermolysis on defective carbon substrates, thus making hydrogen production possible at temperatures just under 1,000 °C (1,270 K; 1,830 °F).
[16] One side benefit of a nuclear reactor that produces both electricity and hydrogen is that it can shift production between the two.
As of 2005, there was sufficient hydrogen demand in the United States that all daily peak generation could be handled by such plants.
Hydrosol-2 is a 100-kilowatt pilot plant at the Plataforma Solar de Almería in Spain which uses sunlight to obtain the required 800 to 1,200 °C (1,070 to 1,470 K; 1,470 to 2,190 °F) to split water.
[19] Material constraints due to the required high temperatures are reduced by the design of a membrane reactor with simultaneous extraction of hydrogen and oxygen that exploits a defined thermal gradient and the fast diffusion of hydrogen.
A "Solar Water Cracker" with a concentrator of about 100 m2 can produce almost one kilogram of hydrogen per sunshine hour.
