Investigation of H Sorption and Corrosion Properties of Sm₂Mn<i>_x</i>Ni_7−<i>x</i> (0 ≤ <i>x</i> < 0.5) Intermetallic Compounds Forming Reversible Hydrides

Abstract

Intermetallic compounds are key materials for energy transition as they form reversible hydrides that can be used for solid state hydrogen storage or as anodes in batteries. ABy compounds (A = Rare Earth (RE); B = transition metal; 2 y AB5] and [AB2] sub-units along the c crystallographic axis. The latter sub-unit brings a larger capacity, while the former one provides a better cycling stability. However, ABy binaries do not show good enough properties for applications. Upon hydrogenation, they exhibit multiplateau behavior and poor reversibility, attributed to H-induced amorphization. These drawbacks can be overcome by chemical substitutions on the A and/or the B sites leading to stabilized reversible hydrides. The present work focuses on the pseudo-binary Sm2MnxNi7−x system (0 ≤ x x > 0.3 leading to larger and flatter isotherm curves, allowing for reversible capacity >1.4 wt %. Regarding corrosion, the binary compound corrodes in alkaline medium to form rare earth hydroxide and nanoporous nickel. As for the Mn-substituted compounds, a new corrosion product is formed in addition to those above mentioned, as manganese initiates a sacrificial anode mechanism taking place at the early corrosion stage.

Keywords

• metallic hydrides
• Ni-<i>M</i>H batteries
• corrosion
• rare earths
• magnetic measurements