Hydrothermal Preparation Of Fe <sub> 2 </ Sub> The O <sub> 3 </ Sub> And A Variety Of Morphologies Of Fe <sub> 2 </ Sub> The O <sub> 3 </ Sub> Hydrogen Storage Properties Of

The paper mainly discussed the preparation of spherical and parallelepiped iron oxide by a hydrothermal route and the hydrogen storage performances of Fe2O3 with different shapes. At the same time, the iron oxides were modified by Mo cations. Then, the effect of Mo on the hydrogen storage performances of Fe2O3 and the mechanism of Mo were investigated.For the preparation of spherical iron oxide, the result showed that: Polyvinylpyrrolidone (PVP) as surfactant played an important role on the morphology of iron oxide synthesized by hydrothermal route. PVP could exist on the surface of particles and connect with the surface of iron oxide particles strongly to form stable chemical bond, which could influence the growth of iron oxide in a certain direction. When PVP served as surfactant and the amount of it was 1.0g, uniform spherical Fe2O3 could be obtained. When PVP was replaced by SDBS as surfactant, the entire shape was sphere but the surface of an individual spherical particle was composed of triangle-like particles that aggregated together via oriented attachment.For the preparation of parallelepiped iron oxide, the result showed that: Polyvinylpyrrolidone (PVP) as surfactant also played an important role on the morphology of parallelepiped iron oxide synthesized by hydrothermal route. At the same time, (NH4)2S2O8 used as the oxidant was indispensable. It could oxidize Fe2+to Fe3+. Also, it could coordinate with iron oxide, which could influence the growth of iron oxide in a certain direction. Without (NH4)2S2O8, the size of iron oxide was not in uniform and the surface of particle was not smooth and the particle was composed of small particles.For the hydrogen storage performances of iron oxide, the result showed that: Compared with hydrogen storage performances of iron oxide without Mo cations, those of the modified samples were increased remarkablely. Among the Mo-modified samples, the modified hollow iron oxide was the best sample:the production temperature was 238℃: the rate of production was high; the hydrogen storage capacity was 4.72 wt%. After 10 cycles, the sample still had a good cyclic stability. The oxidation number of Mo that existed in the form of molybdate species varied from Mo6+ before the redox to Mo4-after the redox. Maybe, it is the valence change of Mo that boosted the decomposition reaction of water. Meanwhile, based on our previous experimental result of Moexisting in the reduced fresh sample and the present experiment, the catalytic effect of Mo cations on the redox performances could be represented as follows:2Mo6++3H2â†'2Mo3++6H+(only for the reduction step of the fresh sample) and the subsequent reversible reaction of 2Mo3-+H2O?2Mo4++H2+O2-(for the oxidation step of the reduced iron oxide) and the reversible change of Mo3+?Mo4+for the subsequent redox cycles.