Simulation and prediction study of hydrogenation/dehydrogenation kinetics based on the universal changing-volume model

Abstract

Considering the expansion/shrinkage of metal hydride particles during hydriding/dehydriding, the hydrogenation/dehydrogenation kinetics cannot be described and predicted as expected. A universal changing-volume model (UCVM) was proposed to simplify the model expression and improve kinetics accuracy, meanwhile a model parameter (ξ) was introduced to address the effect of working conditions on kinetics. Both crystal parameter and density were simulated after crystal geometry optimization based on First-principles calculations, and H2 absorption/desorption experiments of LaNi4.5Co0.5 were employed to verify the availability of UCVM. The experimental results indicated that UCVM owned the highest model precision among several typical models. Moreover, UCVM performed a broad adaptability for other metal hydrides, and its calculation results demonstrated a prominent agreement with the experimental data of FeTi and Mg1.95Ag0.05Ni. In general, the prediction system of UCVM can precisely forecast the kinetics process under various operation conditions, which can be further developed to some liquid-solid and gas-solid catalytic reactions.