Zinc–zinc oxide cycle

For chemical reactions, 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 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.

• Cerium(IV) oxide–cerium(III) oxide cycle
• Copper–chlorine cycle
• Hydrosol-2
• Hybrid sulfur cycle
• Iron oxide cycle
• Sulfur–iodine cycle

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