Oxygen-gas-releasing reaction of Zn ferrite by Xe lamp beam irradiation in air at 1800 K

The oxygen-releasing step of the ZnFe2O4/(ZnO+Fe3O4) system for solar hydrogen production with two-step water splitting using concentrated solar energy was studied in air by irradiation with concentrated Xe lamp beams (solar simulator). The Zn content in the ZnFe2O4 is vaporized in the form of metal zinc, and the oxygen gas is released to generate Fe3O4 in air at 1800 K. The vaporized metal Zn reacts with O2 in air, and is deposited in the form of a ZnO layer on the reaction cell wall. The stability field of the Fe3O4 phase in terms of the O2 partial pressure and the temperature shows that the solid product of the Fe3O4 after the O2-releasing reaction is stable even in 1 atm of O2 at 1800 K. Thus, the O2-releasing reaction (ZnFe2O4=ZnO+2/3Fe3O4+1/6O2) can be applied for obtaining 100% O2 gas in the two-step water splitting using concentrated solar heat.