SIMULATION OF THE DEGRADATION BEHAVIOR OF THE HYDROGEN ABSORPTION KINETICS OF LANI5 UNDER THE CYCLIC OPERATIONS IN H2-CO AND H2-O2

The degradation behavior of the hydrogenation properties of LaNi5 under cyclic operations in mixed gases (H2-O2 and H2-CO) are simulated. For the simulations, the rate equations for the adsorption of CO, O2 and H2 gases are derived and two models which differ in the type of contamination are considered. In the first model the gaseous impurity adsorbs strongly at the surface of the alloy and then completely deactivates some particles which are in contact with it immediately after the mixed gases are introduced during the hydriding reaction. The poisoned particles can no longer absorb hydrogen. In the second model the adsorption energy of the gas impurity is relatively small, and the surface of all particles is contaminated evenly and partially on each cycle. In the former case, the alloy is strongly deactivated by the gaseous impurity and the shapes of the hydrogen absorption kinetic curves do not change with cycling. In the latter case, the effect of the gaseous impurity on the hydrogenation properties of the alloy is relatively mild; however, the hydriding rate is retarded and the shape of the kinetic curve changes continuously with an increasing number of cycles.