JOURNAL of the Tunisian Chemical Society

The reaction of oxygen with the surface of γFe₂O3 has been studied by infrared spectroscopy method. It has been shown that a variety of forms of adsorbed oxygen is produced. The adsorption bands corresponding to the different forms of adsorbed oxygen lie in the 1600 - 800 cm^-1 spectral range. Two species are clearly distinguished: one neutral molecular specie highly polarised which absorbs in the 1500-1540 cm^-1 region and one charged specie O₂^n- with 0 < n < 1 which absorbs in the 1500 - 1200 cm^-1 region. Their thermodesorption in vacum at 250°C is accompanied by sample reduction to Fe₃O₄ state. Hydrogen reacts selectively (according to temperature) with adsorbed molecular oxygen then lattice oxygen. With molecule interacts physically among hydrogen bonds with some O₂^n- species, however dipole-dipole interaction with polarized species is pointed out. At room temperature, propen adsorption leads to chemisorbed species obtained by a reaction with adsorbed oxygen.

H. Batis

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