Thermochemical two-step water-splitting for hydrogen production using Fe-YSZ particles and a ceramic foam device

Fe3O4 supported on cubic yttria-stabilized zirconia (Fe3O4/c-YSZ) is proposed as a promising redox material for the production of hydrogen from water via a thermochemical two-step water-splitting cycle. In this study, the evolution of oxygen and hydrogen during the cyclic reaction was examined using Fe3O4/c-YSZ particles in order to demonstrate reproducible and stoichometric oxygen/hydrogen production through a repeatable two-step reaction. Subsequently, a ceramic foam device coated with Fe3O4 and c-YSZ particles was prepared and examined as a thermochemical water-splitting device in a directly irradiated receiver/reactor hydrogen production system. The Fe3O4/c-YSZ system formed a Fe-containing YSZ (Fe-YSZ) by high-temperature reaction between Fe3O4 and the c-YSZ support at 1400 °C in an inert atmosphere. The reaction mechanism of the two-step water-splitting cycle is associated with the redox transition of Fe2+–Fe3+ ions in the c-YSZ lattice. The Fe-YSZ particles exhibit good reproducibility for reaction with a hydrogen/oxygen ratio of approximately 2.0 throughout repeated cycles. The foam device coated with Fe-YSZ particles was also successful for continual hydrogen production through 32 repeated cycles. A 20–27% ferrite conversion was obtained using 10.5 wt% Fe3O4 loading over an irradiation period of 60 min.