Preliminary investigation on the catalytic mechanism of TiF_3 additive in MgH_2-TiF_3 H-storage system

摘要

A combined structure/property investigation is performed to understand the catalytic effect of TiF_3 additive on the absorption/desorption reactions of MgH_2. It was found that both TiH_2 and MgF_2 phases identified by x-ray diffraction cannot explain the observed kinetic enhancement in the MgH_2-TiF_3 system, whether they are incorporated in a direct or an in situ manner. In combination with the comparative investigation on the catalytic activity of TiF_3 and its analog TiCl_3, as well as the samples milled under inert and reactive atmospheres, we propose that the catalytically active species is a multicomponent metastable phase composed of host Mg, transition metal Ti, and F anion, the catalytic activity of which is dependent on its interaction with the surrounding chemical environment.