Hydrogen storage and production by redox of iron oxide for polymer electrolyte fuel cell vehicles

Pseudo-storage of hydrogen and its recovery by redox of iron oxide have been proposed as a new method of the storage and supply of hydrogen for PEFC vehicles. Among the additives to iron oxide tested, Al, Cr, Zr, Ga and V were the effective elements enhancing both the reduction with H2 (storage of H2) and reoxidation with water (recovery of H2) of the iron oxide (3Fe+4H2O⇌Fe3O4+4H2) at low temperatures (<400°C). The additives moderated the sintering of iron oxide markedly with repeated redox cycles. It is suggested that another important role of additives is to activate H2 and H2O at the surface of iron oxide or to enhance the diffusion of O2− as a result of the formation of compound oxides between the additive and iron oxide.