H2 Evolution Reactivity of Carbon-Bearing Ni(II) Ferrite (CBNF)

Two-step water-splitting with a carbon-bearing Ni(II) ferrite (CBNF) at 300°C has been studied. The chemical analysis of the solid phase showed that the CBNF was gradually oxidized during repeated water splitting, but the evolved H2 amount is 1.5-2 times larger than that expected &om the oxidation of the CBNF. Following two types of hydrogen evolution reactions are considered to be participated: Type I is the water splitting by the activated form of CIO layer(&), where the activated form changes to the origlnal form (P,,), Type II is hydrogen evolution by the oxidation of CIO layer, where the original CIO layer fom(P,,) changes to an oxidized form (P,,). The amount of released oxygen was about 40-80% of the amount estimated from the amount of hydrogen gas evolved by the Type I reaction. Thus, the stoichiometry of the above two steps has been demonstrated.