Zinc–zinc oxide cycle

The zinc–zinc oxide cycle or Zn–ZnO cycle is a two step thermochemical cycle based on zinc and zinc oxide[1] for hydrogen production[2] with a typical efficiency around 40%.[3]

The Zn/ZnO cycle

Process description

The thermochemical two-step water splitting process uses redox systems:[4]

• Dissociation: ZnO → Zn + 1/2 O₂
• Hydrolysis: Zn + H₂O → ZnO + H₂

For the first endothermic step concentrating solar power is used in which zinc oxide is thermally dissociated at 1,900 °C (3,450 °F) into zinc and oxygen. In the second non-solar exothermic step zinc reacts at 427 °C (801 °F) with water and produces hydrogen and zinc oxide. The temperature level is realized by using a solar power tower and a set of heliostats 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

1. Solar Hydrogen Production from a ZnO/Zn Thermo-chemical Cycle Archived July 24, 2008, at the Wayback Machine
2. Project PD10
3. Novel Method for solar hydrogen generation Archived February 5, 2009, at the Wayback Machine
4. Solar thermal ZnO-decomposition

External links

• H2 formation by zinc hydrolysis in a hot wall aerosol flow reactor