Statistical physics modeling of hydrogen desorption from LaNi4.75Fe0.25: Stereographic and energetic interpretations

Statistical physics treatment is used to study the desorption of hydrogen on LaNi4.75Fe0.25, in order to obtain new physicochemical interpretations at the molecular level. Experimental desorption isotherms of hydrogen on LaNi4.75Fe0.25 are fitted at three temperatures (293 K, 303 K and 313 K), using a monolayer desorption model. Six parameters of the model are fitted, namely the number of molecules per site nα and nβ, the receptor site densities NαM and NβM, and the energetic parameters Pα and Pβ. The behaviors of these parameters are discussed in relationship with desorption process. A dynamic study of the α and β phases in the desorption process was then carried out. Finally, the different thermodynamical potential functions are derived by statistical physics calculations from our adopted model.