Two-step water-splitting at 1273–1623K using yttria-stabilized zirconia-iron oxide solid solution via co-precipitation and solid-state reaction

Abstract

Reactive ceramics are investigated for potential use in a rotary-type solar reactor. The two-step water-splitting process, which consists of O 2 -releasing (MO oxidized =MO reduced +1/2O 2 ) and H 2 -generation (MO reduced +H 2 O(g)=MO oxidized +H 2 ) reactions with yttria-stabilized zirconia (YSZ)-iron oxide solid solutions prepared by co-precipitation and solid-state reaction, is examined at temperatures of 1623 K for O 2 release and 1273 K for H 2 generation. The YSZ-iron oxide solid solutions with a single phase are obtained at mole ratios lower than 15% and 20% of iron ions to total cations (Fe 3+ , Zr 4+ , Y 3+ ) by co-precipitation and the solid-state reaction, respectively. The two-step water-splitting process using YSZ-iron oxide solid solutions prepared by both preparation methods are repeated successfully. The amount of O 2 gas evolved per weight of the sample (ml/g) is observed to increase with the iron content of the YSZ-iron oxide solid solution because of the high reactivity of iron ions in the solid solution. The maximum amounts of H 2 and O 2 gases evolved in the two-step water-splitting process with the YSZ-iron oxide solid solution were 0.89 and 1.2 ml/g, respectively.