LaNiH

LaNiH is a ternary hydride composed of lanthanum, nickel and hydrogen. The compound adopts a face‑centered cubic lattice in which hydrogen atoms occupy octahedral voids between La and Ni atoms. The lattice parameters are reported to be a = 3.92 Å and a hydrogen content of approximately one hydrogen per formula unit.

Synthesis of LaNiH is typically achieved by direct hydrogenation of a stoichiometric mixture of lanthanum metal, nickel powder and metal hydride precursors under high pressure. A common method involves sealing the starting materials in a quartz tube, evacuating the tube and back‑filling with hydrogen to a pressure of 20–30 MPa, followed by heating to 500–600 °C for several hours. The resulting product is a fine, grey powder that is stable under inert atmosphere but slowly oxidises on prolonged exposure to air.

Physically, LaNiH is a lightweight solid with a density of about 5.5 g cm⁻³. It shows metallic electrical conductivity, with a room‑temperature resistivity of roughly 15 µΩ cm. The compound is magnetic‑susceptible, displaying a Curie–Weiss behavior at high temperature and a transition to a paramagnetic state below 150 K. Neutron diffraction studies indicate that hydrogen atoms remain partially disordered, which contributes to a modest thermal expansion coefficient.

Potential applications of LaNiH include hydrogen storage, where its moderate release temperature (~350 °C) combined with a high gravimetric hydrogen density (~2.4 wt %) make it a candidate for low‑temperature fuel cell systems. The Ni site also provides catalytic activity for hydrogenation reactions, and the compound has shown promise as a catalyst support in certain electrochemical processes. However, its chemical reactivity with moisture limits practical deployment, and further research is required to improve its stability and to scale up synthesis for commercial use.