Storage and supply of pure hydrogen mediated by the redox of iron oxides

Methods for the storage and supply of pure H-2 are proposed based on the reduction of iron oxide with H-2 (Fe3O4 + 4H(2) -->- 3Fe + 4H(2)O) followed by the oxidation of the iron metal with H2O (3Fe + 4H(2)O --> Fe3O4 + 4H(2)). In addition, production of pure H-2 from CH4 is proposed based on the reduction of iron oxides with CH4 (Fe3O4 + CH4 --> 3Fe + CO2 + 2H(2)O) and the subsequent oxidation of iron metal with H2O (3Fe + 4H(2)O --> Fe3O4 + 4H(2)). Iron oxides without other metal elements were deactivated quickly during these redox cycles due to sintering irrespective of the reductant (H-2 or CH4). The addition of metal cations such as Al, Sc, Ti, V, Cr, Ga, Zr or Mo cations mitigated the sintering of iron oxides and/or iron metals during repeated redox cycles. The addition of metal species such as Cu, Ni, Pt and Rh promoted the reactivity of iron oxides in the redox reaction at lower temperatures. The favorable effects of the addition of these metal species on the redox of iron oxides were observed for both reduction with H-2 or with CH4. Therefore, iron oxide modified with these cations and metals can supply pure H-2 continuously throughout these redox cycles. The favorable effects of the metal species added to iron oxides were investigated based on the local structures.