Water splitting
Water splitting is the general term for a chemical reaction in which water is separated into oxygen and hydrogen. Efficient and economical water splitting would be a key technological component of a hydrogen economy. Various techniques for water splitting have been issued in water splitting patents in the United States. In photosynthesis, water splitting donates electrons to the electron transport chain in photosystem II.
Electrolysis of water is the decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to an electric current being passed through the water. In chemistry and manufacturing, electrolysis is a method of separating chemically bonded elements and compounds by passing an electric current through them. One use of electrolysis of water or artificial photosynthesis (photoelectrolysis in a photoelectrochemical cell) is to produce hydrogen. Recently, researchers have shown that water splitting can be broken into two discrete steps using polyoxometalate based redox mediators.
Power to gas production schemes, the excess power or off peak power created by wind generators or solar arrays is used for load balancing of the energy grid by storing and later injecting the hydrogen into the natural gas grid.
Production of hydrogen from water requires large amounts of energy and is uncompetitive with its production from coal or natural gas. Potential electrical energy supplies include hydropower, wind turbines, or photovoltaic cells. Usually, the electricity consumed is more valuable than the hydrogen produced so this method has not been widely used. Other potential energy supplies include heat from nuclear reactors and light from the sun. Hydrogen can also be used to store renewable generated electricity when it is not needed (like the wind blowing at night) and then used to meet power needs during the day or to fuel vehicles. The storable quality of hydrogen helps make hydrogen an enabler of the wider use of renewables, and internal combustion engines. (See hydrogen economy.)
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