Monoclinic zirconia-supported Fe sub(3O) sub(4) for the two-step water-splitting thermochemical cycle at high thermal reduction temperatures of 1400-1600 degree C

Two-step thermochemical water-splitting using monoclinic ZrO sub(2-supported Fe) sub(3)O sub(4 (Fe) sub(3)O sub(4/m-ZrO) sub(2)) for hydrogen production was examined at high thermal reduction temperatures of 1400-1600 degree C. After thermal reduction of Fe sub(3O) sub(4)/m-ZrO sub(2, the reduced sample was quenched in liquid nitrogen, and was subsequently subjected to the water-decomposition step at 1000 degree C. Quenching of the solid sample was conducted for analysis of the chemical reactions, such as phase transitions, occurring at high-temperature. The hydrogen productivity of Fe) sub(3)O sub(4 on a m-ZrO) sub(2) support and the conversion of Fe sub(3O) sub(4) to FeO were significantly enhanced with higher thermal reduction temperatures. The Fe sub(3O) sub(4)-to-FeO conversion reached 60% when the Fe sub(3O) sub(4)/m-ZrO sub(2 was thermally reduced at 1600 degree C. The phase transition of m-ZrO) sub(2) support to tetragonal ZrO sub(2 (t-ZrO) sub(2)) did not occur during the thermal reduction at 1400-1500 degree C, but it did proceed slightly at 1600 degree C. Fe ions from Fe sub(3O) sub(4) did not enter the ZrO sub(2 lattice during high-temperature thermal reduction. Thus, the Fe) sub(3)O sub(4 loaded on a m-ZrO) sub(2) support can continuously contribute as a Fe sub(3O) sub(4)-FeO redox reactant for thermochemical water-splitting at high-temperatures of 1400-1600 degree C.