Water splitting

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 [ [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 ] ] 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 or artificial photosynthesis (photoelectrolysis in a photoelectrochemical cell) 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.")

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 thermochemical processes used to produce hydrogen. The S-I cycle consists of three chemical reactions 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, [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] 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. Recently, this has been successful in splitting water into hydrogen and oxygen using an artificial compound called Nafion. [ [http://www.eurekalert.org/pub_releases/2008-08/mu-mtl081408.php] ]

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 [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 ]

Patents

* Vion, US patent|28793, "Improved method of using atmospheric electricity", June 1860.

References

See also

*Water gas shift reaction