Catalytic effect of monoclinic WO_3, hexagonal WO_3 and H_(0.23)WO_3 on the hydrogen sorption properties of Mg

摘要

The H sorption properties of mixtures Mg + WO_3 (having various structures) and Mg + H_(0.23)WO_3 are reported. First, the higher conversion of Mg into MgH_2 during reactive mechanical grinding (under 1.1 MPa of H_2) for higher WO_3 content is due to the improvement of the milling efficiency. Then, it is shown that the hydrogen absorption properties are almost independent of the crystal structure of the catalyst and that only the particles' size and the specific surface play a major role. Finally, for the desorption process, it appears that the chemical composition and structure of the catalyst, together with the particle size and specific surface have an effect.