Effect of Ni substitution on hydrogen storage properties of Zr_0.8Ti_0.2Co_1-xNi_x (x = 0, 0.1, 0.2, 0.3) alloys

Zr_0.8Ti_0.2Co_1-xNi_x (x = 0, 0.1, 0.2, 0.3) alloys were prepared by vacuum arc-melting method. The microstructure and hydrogen storage properties including cyclic stability, disproportionation rate and hydriding kinetics of the alloys at 573 K and 673 K were studied respectively. X-ray diffraction (XRD) analyses show that all original alloys are consist of single ZrCo phase. At 573 K, with Ni content increasing, the hydrogen storage capacity retention of the alloys increases from 58.7% (x = 0) to 76.3% (x = 0.3) obviously after 15 hydriding/dehydriding cycles which can be mainly attributed to the enhancement of anti-pulverization capability for the alloys after Ni partial substitution for Co. However, at 673 K, hydrogen-induced disproportionation becomes the main factor for the deterioration of hydrogen storage properties for the alloys. Kinetics test shows that the hydriding speed of the alloys at 573 K increases gradually with Ni content increasing since Ni acts as a catalyst during hydrogen absorption process. In addition, the hydrogen desorption curves at 673 K reveal that Ni partial substitution for Co deteriorates the anti-disproportionation property of the alloys slightly.