Effect of Co content on microstructure evolution and hydrogen storage properties of La0.6Y0.15Ca0.9Mg1.05Ni9Cox alloys

Abstract

Superlattice hydrogen storage alloys exhibit advantages such as easy activation and high hydrogen storage capacity. However, compared with commercial AB₅-type hydrogen storage alloys, the hydrogen desorption platform pressure and effective hydrogen storage capacity of superlattice hydrogen storage alloys are comparatively lower, which makes it difficult to meet the demand of gas-solid hydrogen storage devices. In this work, we have successfully prepared La_0.6Y_0.15Ca_0.9Mg_1.05Ni₉Co_x (x = 0, 0.25, 0.45, 0.65, 0.85) superlattice hydrogen storage alloys and systematically investigated the effects of Co content on the structures and properties of this series of alloys. The results of XRD refinement analysis show that the increase of Co content can cause the AB₃-type phase to decrease gradually and the AB₅-type phase to increase gradually in the alloy. Thermodynamic analyses of hydrogen absorption and desorption indicate that with the increase of Co content, the desorption platform pressure of alloy increases gradually, while the maximum hydrogen storage capacity decreases gradually. Notably, when x = 0.45, the alloy exhibits a maximum effective hydrogen storage capacity of 1.60 wt% under conditions of 298 K and 0.1 MPa, with a hydrogen desorption platform pressure of 0.4 MPa and a hydrogen storage capacity retention rate of 86.93 % after 200 cycles. The overall hydrogen storage performance of this alloy surpasses that of the majority of the superlattice hydrogen storage alloys reported in the literature. These findings provide guidance for the practical application of superlattice hydrogen storage alloys in gas-solid hydrogen storage devices.