Interaction of the RNi 5In (R = La, Ce and Nd) compounds with hydrogen

Abstract

LaNi 5In, NdNi 5In and CeNi 5In reversible hydrogen absorbers were hydrogenated at room temperature under hydrogen pressure up to 10.0 MPa, forming LaNi 5InH 1.8, NdNi 5InH 0.9 and CeNi 5InH 0.8 hydrides. These were characterised by X-ray diffraction. These hydrides have the same crystal structure as original metal matrix with slightly expanded unit cell (Δ a⧸ a 0 = (0.4–0.8)%; Δ c⧸ c 0 = (0.6–1.2)%; Δ V⧸ V 0 = (1.4–2.8)%. Isotherms of hydrogen absorption-desorption in LaNi 5In–H systems were measured at 292.0, 328.5 and 355.5 K. Enthalpy change for reaction with hydrogen was determined. The values ΔH = −(35.9±2.2) kJ⧸(mole H 2) on formation of the hydride and ΔH = (33.2±1.6) kJ⧸(mole H 2) on reverse transition were obtained. The RNi 4In ( R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) do not interact with hydrogen under the above conditions. Catalytic influence of RNi 5In phase on hydrogenation of the RNi 4In phase was observed in the case of Pr-containing compounds.