Enhancement of hydrogenation kinetics and thermodynamic properties of ZrCo 1-x Cr x (x=0-0.1) alloys for hydrogen storage

The vacuum arc melting method was used to prepare ZrCo1-xCrx (x=0, 0.025, 0.05, 0.075, 0.1) alloys. Afterward, the crystal structure, hydrogenation kinetics, thermodynamic properties, and disproportionation performance of ZrCo1-xCrx (x=0-0.1) alloys were investigated. The X-ray diffraction spectra demonstrated that ZrCo1-xCrx (x=0-0.1) alloys contained ZrCo and ZrCo2 phases, and their corresponding hydrides consisted of ZrCoH3 and ZrH phases. The activation behaviors of Cr-substituted samples were significantly promoted. The activation time of ZrCo was 7715 s while that of ZrCo0.9Cr0.1 was 195 s. The improvement of kinetics can be attributed to the catalytic hydrogenation of ZrCr2. The activation energy for the hydrogenation of ZrCo was 44.88 kJ mol-1 H2 and decreased to 40.34 kJ mol-1 H2 for ZrCo0.95Cr0.05. The plateau pressure and width of the pressure-composition-temperature curves decreased slightly as Cr content increased. The extent of disproportionation of ZrCo was 83.68% after being insulated at 798 K for 10 h and decreased slightly to 70.52% for ZrCo0.9Cr0.1. The improvement of anti-disproportionation performance can be attributed to increase in the activation energy of disproportionation from 167.46 kJ mol-1 H2 for ZrCo to 168.28 kJ mol-1 H2 for ZrCo0.95Cr0.05.