Structural and hydrogen sorption properties of SmNi5−xAlx system – An experimental and theoretical study

• A series of SmNi5−xAlx-hydrogen systems were prepared examined for hydrogen sorption.
• DFT calculations were employed to model the systems.
• Hydrogen sorption cycling stability of the system SmNi4.5Al0.5 was investigated.
• Novel insights into structural changes by rehydrogenation of the system are given.

A series of ternary alloys of general formula SmNi5−xAlx (x=0.25,0.5,0.75,1,1.5,2,2.5) was prepared by melting corresponding stoichiometric mixtures of samarium, nickel and aluminium in an arc furnace under argon. From X-ray powder diffraction lattice parameters are determined and it is found that hexagonal structure of P6/mmm space group is retained for all considered values of x. Hydrogen absorption ability and thermodynamic quantities of the systems are determined by pressure-composition desorption isotherms. The obtained properties are compared with those of previously reported SmNi5 and SmNi5−xGax system. Cycling stability of the SmNi4.5Al0.5 system was investigated. DFT calculations were performed for selected members of the system and the results are discussed with regard to experiment. The present work extend previous efforts to screen intermetallic compounds of the LaNi5 type and their hydrides. A combined experimental and computational approach provides a detailed insight into the mechanistic details of hydrogen storage action of these technologically important systems.