Water splitting
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2008-06-18T19:18:25Z
Gaius Cornelius
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'''Water splitting''' is the general term for a [[chemical reaction]] in which [[water]] is converted into [[oxygen]] and [[hydrogen]]. Water splitting is actively researched because demand for cheap hydrogen is expected to rise with the new [[hydrogen economy]]. Various techniques for water splitting have been issued in water splitting patents <ref>[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=0&p=1&f=S&l=50&Query=ttl%2F%22water+splitting%22%0D%0A&d=PTXT Patent Database Search Results: ttl/"water splitting" in US Patent Collection<!-- Bot generated title -->]</ref> in the United States.
==Methods==
===Artificial===
In chemistry and manufacturing, electrolysis is a method of separating chemically bonded elements and compounds by passing an electric current through them. One important use of [[electrolysis of water]] is to produce hydrogen. This has been suggested as a way of shifting society toward using hydrogen as an [[energy carrier]] for powering electric motors and internal combustion engines. (''See [[hydrogen economy]].'')
[[thermolysis|Thermal decomposition]], also called [[thermolysis]], is defined as a chemical reaction whereby a chemical substance breaks up into at least two chemical substances when heated. Water, when heated to well over 2000 degrees Celsius, breaks up into its components - hydrogen and oxygen.
===Natural===
Water splitting donates electrons to power the electron transport chain in [[photophosphorylation]] of [[photosynthesis]].
==Research==
The [[sulfur-iodine cycle]] (S-I cycle) is a series of [[Thermochemistry|thermochemical]] processes used to [[Hydrogen production|produce hydrogen]]. The S-I cycle consists of three [[chemical reaction]]s whose net reactant is [[water]] and whose net products are [[hydrogen]] and [[oxygen]]. All other chemicals are recycled. The S-I process requires an efficient source of heat.
Research is being conducted over [[photocatalysis]],<ref>Strategies for the Development of Visible-light-driven Photocatalysts for Water Splitting Akihiko Kudo, Hideki Kato1 and Issei Tsuji Chemistry Letters Vol. 33 (2004) , No. 12 p.1534</ref> the acceleration of a photoreaction in the presence of a catalyst. Its comprehension has been made possible ever since the discovery of water electrolysis by means of the titanium dioxide. [[Artificial photosynthesis]] is a research field that attempts to replicate the natural process of photosynthesis, converting sunlight, water and carbon dioxide into carbohydrates and oxygen.
[[High-temperature electrolysis]] (also HTE or [[steam electrolysis]]) is a method currently being investigated for the production of hydrogen from water with oxygen as a by-product. Other research includes [[thermolysis]] on defective [[carbon]] substrates, thus making hydrogen production possible at temperatures just under 1000°C<ref>{{cite paper
| author = Kostov, M. K.; Santiso, E. E.; George, A. M.; Gubbins, K. E.; and Nardelli, M. Buongiorno
| title = Dissociation of Water on Defective Carbon Substrates
| publisher = Physical Review Letters
| date = 2005
| url =http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRLTAO000095000013136105000001&idtype=cvips&prog=normal
| format = [[PDF]]
| accessdate = 2007-11-05 }}</ref>
==Patents==
* Vion, {{US patent|28793}}, "Improved method of using atmospheric electricity", June 1860.
== References ==
{{Reflist}}
== See also ==
*[[Water gas shift reaction]]
[[Category:Environmental chemistry]]
[[Category:Fuels]]
[[Category:Hydrogen production]]
[[es:Separación del agua]]
[[nl:Ontleding van water]]