Electrochemical synthesis of a hydrogen storage material based on lanthanum and nickel intermetallics in the equimolar KCl–NaCl melt

Abstract

Co-reduction of lanthanum and nickel ions on inert tungsten and active nickel electrodes were studied using the methods of cyclic chronovoltammetry, chronopotentiometry and open circuit chronopotentiometry in equimolar KCl–NaCl at 973 K. When both lanthanum and nickel ions are present in equimolar KCl–NaCl, the voltammetry dependences demonstrate the nickel ions reduction wave in the region of potentials –(0.00–0.1) V and lanthanum ions reduction wave in the region of potentials –(1.85–1.9) V relative to a silver chloride reference electrode. There are two more reduction waves on the opposite sides of voltammograms in the regions of potentials –(1.5–1.6) V and –(1.75–1.8) V. These waves are associated with the reduction of lanthanum ions and their depolarization on metallic nickel preliminarily deposited on the tungsten electrode, which results in the formation of intermetallic LaxNiy phases. The (E–t) dependences of open circuit chronopotentiometry demonstrate a delay plateau, which corresponds to the time required for dissolution of separate phases of intermetallic compounds. LaNi2 and LaNi5 intermetallic phases were electrochemically synthesized at a definite concentration of lanthanum and nickel chlorides in equimolar KCl–NaCl. The synthesized lanthanum and nickel intermetallic compounds were characterized by the X-ray diffraction analysis, scanning electron microscopy and photon correlation spectroscopy.