Methods for the storage and formation of pure hydrogen were demonstrated based on the reduction of magnetite with hydrogen (Fe3O4 + 4H(2) -> 3Fe + 4H(2)O), followed by oxidation of iron metal with water vapor (3Fe + 4H(2)O -> Fe304 + 4H(2)). Iron oxides containing Cr cations produced hydrogen repeatedly through the redox reactions, whereas pure iron oxide was deactivated quickly for the redox due to sintering. Addition of Cu, Ni or Rh to iron oxides containing Cr cations enhanced the formation rate of hydrogen through the oxidation with water vapor at 573 K. These iron oxides can store and form hydrogen repeatedly through the redox. In addition, formation of hydrogen from synthesis gas or methane was demonstrated based on the reduction of iron oxides with synthesis gas or methane, followed by oxidation of iron metal with water vapor. The iron oxides containing both Cr and Ni species can produce hydrogen repeatedly through the redox reactions. (c) 2004 Elsevier B.V. All rights reserved.