[[Image:Zinc zinc-oxide thermochemical cycle.jpg|350 px|right|The Zn/ZnO cycle]] For [[chemical reaction]]s, the '''zinc–zinc oxide cycle''' or Zn–ZnO cycle is a two step [[thermochemical cycle]] based on [[zinc]] and [[zinc oxide]]<ref>[http://www.solarpaces.org/Tasks/Task2/SHP.HTM Solar Hydrogen Production from a ZnO/Zn Thermo-chemical Cycle] {{webarchive |url=https://web.archive.org/web/20080724183416/http://www.solarpaces.org/Tasks/Task2/SHP.HTM |date=July 24, 2008 }}</ref> for [[hydrogen production]]<ref>{{Cite web |url=http://www.hydrogen.energy.gov/pdfs/review06/pd_10_weimer.pdf |title=Project PD10 |access-date=2008-12-21 |archive-date=2009-02-05 |archive-url=https://web.archive.org/web/20090205122514/http://www.hydrogen.energy.gov/pdfs/review06/pd_10_weimer.pdf |url-status=dead }}</ref> with a typical efficiency around 40%.<ref>[http://www.switt.ch/files/technologien/Solar%20Hydrogen%20Production_04-014.pdf Novel Method for solar hydrogen generation] {{webarchive |url=https://web.archive.org/web/20090205122515/http://www.switt.ch/files/technologien/Solar%20Hydrogen%20Production_04-014.pdf |date=February 5, 2009 }}</ref>
==Process description== The thermochemical two-step [[water splitting]] process uses [[redox]] systems:<ref>{{Cite web |url=http://solar.web.psi.ch/data/research/zno/roca/ |title=Solar thermal ZnO-decomposition |access-date=2006-05-05 |archive-date=2006-05-05 |archive-url=https://web.archive.org/web/20060505180329/http://solar.web.psi.ch/data/research/zno/roca/ |url-status=dead }}</ref>
*[[Dissociation (chemistry)|Dissociation]]: [[Zinc oxide|ZnO]] → [[Zinc|Zn]] + 1/2 O<sub>2</sub> *[[Hydrolysis]]: [[Zinc|Zn]] + [[Water (molecule)|H<sub>2</sub>O]] → [[Zinc oxide|ZnO]] + [[Hydrogen|H<sub>2</sub>]]
For the first [[endothermic]] step [[concentrating solar power]] is used in which zinc oxide is [[Thermal decomposition|thermally dissociated]] at {{convert|1900|°C|°F}} into zinc and oxygen. In the second non-solar [[exothermic]] step zinc reacts at {{convert|427|°C|°F}} with water and produces [[hydrogen]] and zinc oxide. The temperature level is realized by using a [[solar power tower]] and a set of [[heliostat]]s to collect the [[solar thermal energy]].
==See also== * [[Cerium(IV) oxide–cerium(III) oxide cycle]] * [[Copper–chlorine cycle]] * [[Hydrosol-2]] * [[Hybrid sulfur cycle]] * [[Iron oxide cycle]] * [[Sulfur–iodine cycle]]
==References== {{reflist}}
==External links== * [https://web.archive.org/web/20110706230820/http://www.ltnt.ethz.ch/people/bburg/MRS05_Burg.pdf H2 formation by zinc hydrolysis in a hot wall aerosol flow reactor]
{{DEFAULTSORT:Zinc-zinc oxide cycle}} [[Category:Inorganic reactions]] [[Category:Hydrogen production]] [[Category:Zinc]] [[Category:Zinc oxide]]