Absorption and desorption of hydrogen in Ti_1.02Cr_1.1Mn_0.3Fe_0.6RE_0.03: experiments, characterization and analytical...

In this work, the absorption and desorption isotherms of hydrogen on Ti_1.02Cr_1.1Mn_0.3Fe_0.6RE_0.03 (RE = La, Ce, Ho) metals were collected at three temperatures under the same experimental conditions. This was carried out in order to determine the rare earth effect on the hydrogen storage performance of the Ti_1.02Cr_1.1Mn_0.3Fe_0.6 metal. The equilibrium data showing the hydrogen absorbed/released amounts per unit of absorbent mass have provided useful details to describe the absorption/desorption processes. Indeed, statistical physics formalism is appealing to ascribe advanced interpretations to the complexation mechanism. The physico-chemical parameters included in the model analytical expression are numerically determined from the experimental data fitting. We have found that the model can describe the complexation process through steric parameters such as the site densities (N _1m and N _2m), the numbers of atoms per site (n ₁ and n ₂) and energetic parameters (P ₁ and P ₂). The behavior of each parameter is examined in relation to the sorption mechanism. Overall, the energetic interpretation reveals that the desorption and absorption of H-gas in the Ti_1.02Cr_1.1Mn_0.3Fe_0.6RE_0.03 alloys can be characterized by chemical interactions. In addition, the expression of the appropriate model is exploited to determine the thermodynamic potential functions that describe the absorption phenomenon.