Enhancement of hydrogenation kinetics and thermodynamic properties of ZrCo_1-xCr_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.