Effects of Mo substitution on the kinetic and thermodynamic characteristics of ZrCo1-xMox (x = 0–0.2) alloys for hydrogen storage

In this study, ZrCo1-xMox (x = 0, 0.05, 0.1, 0.15, 0.2) alloys were prepared via vacuum arc-melting method. The effects of substituting Co with Mo on the structure, initial activation behaviors, and thermodynamic properties of the afore-mentioned alloys were systematically investigated. The results showed that ZrCo1-xMox (x = 0, 0.05, 0.1, 0.15) alloys exhibited a single ZrCo phase and their corresponding hydrides, a ZrCoH3 phase. Furthermore, ZrCo0.8Mo0.2 alloy consisted of ZrCo phase and a trace of ZrMo2 phase, and the hydride contained ZrCoH3 and ZrH phases. As the Mo content was increased, the initial activation period decreased significantly from 19277 s for ZrCo to 576 s for ZrCo0.8Mo0.2, which was closely related to the catalytic effect of ZrMo2. The plateau width of pressure composition temperature curves were shortened, and the equilibrium pressures of hydrogen desorption decreased slightly as Mo content increased. Additionally, the experiments showed that the anti-disproportionation performance was greatly improved by Mo substitution. The extent of disproportionation decreased from 64.28% for ZrCo to 24.11% for ZrCo0.8Mo0.2. The positive effect of Mo substitution on improving the anti-disproportionation property of ZrCo alloy was attributed to the reduction of hydrogen atom in 8f2 and 8e sites, which decreased the driving force of the disproportionation reaction.