Experimental and numerical study of hydrogen adsorption by the Ni0.6Mg0.4Fe2O4 compound

Abstract

This paper proposes an experimental and numerical study of the hydrogen storage properties of the Ni0.6Mg0.4Fe2O4 compound. Firstly, the sol-gel method was used to synthesize the compound Ni0.6Mg0.4Fe2O4. Second, the synthesized compound's morphological and structural properties were ascertained using X-ray and SEM techniques. Third, the experimental hydrogen adsorption's kinetics and isotherms were carried out. At last, the experimental hydrogen adsorption isotherms were compared to a mathematical model based on the formalism of statistical physics. With the use of this model, it was possible to ascertain the following: on the one hand, the stereographic parameters involved in the adsorption process, such as the number of receptor sites (n1 and n2), their density (Nm1 and Nm2), as well as the energy parameters (P1 and P2) and the energies of adsorption for each type of site (ΔEads1 and ΔEads2). On the other hand, the thermodynamic functions that regulate the hydrogen adsorption reaction, such as the internal and Gibbs energies, as well as the entropy versus temperature and pressure. Ni0.6Mg0.4Fe2O4 has a significant hydrogen storage capacity (0.15 wt %) at moderate temperatures. The numerical results showed that hydrogen is inserted into two types of interstitial sites via an exothermic process.