Electrochemical hydrogenation of solid solutions based on the intermetallic compound SmNi5

The electrochemical hydrogenation of SmNi 5-xMx phases ( M = In; In+Sn) and the binary compound SmNi 5 has been studied for the first time by X-ray diffraction, scanning electron microscopy, energy-dispers ive X-ray spectroscopy, and X-ray fluorescence spectros copy. All these phases crystallize in hexagonal CaC u5type structures. The solubility of In or In+Sn in the binary compound SmNi 5 is not higher than 5.0-5.5 at.%, which can be explained by the large difference betw een the atomic radii of the doping components (In, Sn) and nickel. At charging to the 3 H/f.u. level (current density 1.0 mA/cm) the electrodes based on the binary, ternary and quaternary phases demonstrated maxima o f 2.41, 2.52, and 2.72 H/f.u., respectively. The mo st geometrically advantageous sites in the initial str uctures are octahedral voids (Wyckoff position 3 f), where the coordination polyhedron of the H-atom is an oct ahedron of composition [HSm2M4]. The results of the spectral analysis showed that the In-doped electrod e lost In in specific interactions of the surface with the electrolyte during the electrochemical process, in contrast to the other electrodes, which are stable (the qualitative and quantitative compositions of the observed phases remained unchanged).