Theoretical study of hydrogen sorption on LaNi5 using statistical physics treatment: microscopic and macroscopic investigation

In the present work, experimental absorption isotherms of hydrogen in LaNi5 at three temperatures have been fitted using a monolayer model treated by statistical physics by means of the grand canonical ensemble. Six parameters of the model are fitted, namely two numbers of absorbed atoms per, site n1 and n2, two receptor site densities, N1M and N1M and two energetic parameters, P1 and P2. The behaviors of these parameters are discussed in relationship with absorption process. Starting from the monolayer model, we determined the absorption energies which are typically ranged between 85 and 101 kJ/mol comparable to usual chemical bond energies. Calculated thermodynamic potentials such as internal energy (Eint) and Gibbs free energy (G) suggested that the absorption processes was exothermic and spontaneous.