Solar thermochemical process for hydrogen production using ferrites

A two-step water splitting process using the ZnFe2O4/Zn/Fe3O4 reaction system was proposed for H2 generation utilizing concentrated solar heat. The mixture of Zn and Fe3O4 was heated to 873 K in flowing steam with an Ar carrier gas, and the H2 gas was generated at 93.4% of the theoretical yield for the reaction of 3Zn+2Fe3O4+4H2O=3ZnFe2O4+4H2 (H2 generation step). The XRD and Mössbauer spectroscopy showed that the Zn-submitted ferrite (ZnxFe3−xO4; 0.2≤x≤1) (main solid product) and ZnO (minor) were formed in the solid products after the H2 generation reaction. The ZnFe2O4 product, which was formed after the H2 generation step during the two-step water splitting process with the ZnFe2O4/Zn/Fe3O4 system, could be decomposed into Zn (and ZnO) and Fe3O4 by the Xe beam irradiation at 1900 K after 3 min with a 67.8% yield for the reaction of 3ZnFe2O4=3Zn+2Fe3O4+2O2 (O2 releasing step=solar thermal step).