Effect of substituting Al for Co on the hydrogen-storage performance of La0.7Mg0.3Ni2.6AlxCo0.5−x (x = 0.0–0.3) alloys

La0.7Mg0.3Ni2.6AlxCo0.5−x (x = 0.0–0.3) alloys were prepared by induction melting, and the effects of partially substituting Al for Co on the structure and hydrogen-storage properties of the alloys were investigated systematically. It is found that La(Ni, Co, Al)5 phase with hexagonal CaCu5-type structure, LaNi3 phase with PuNi3 structure and MgNi2 phase exist as the main phases in La0.7Mg0.3Ni2.6AlxCo0.5−x (x = 0.0–0.3) alloys, and the cell volume of the La(Ni, Co, Al)5 phase increases with the amount of Al added. The results show that the substitution of Al for Co can reduce the plateau pressure and the hysteresis between hydrogen absorption and desorption, and improve the hydrogen-absorption capacity and thermal stability of the hydride. Moreover, the addition of Al can delay the oxidation of the surface layer of the alloy electrodes in electrolyte, slow down the capacity degradation and prolong the cycling lifetime, and enhance the electrocatalytic activity of the hydrogen-storage electrodes for hydrogen oxidation.