Experimental and theoretical investigation of the cycle durability against CO and degradation mechanism of the LaNi_5 hydrogen storage alloy

摘要

From both the experimental and theoretical aspects we have investigated the cycle durability against CO and degradation mechanism of the hydrogen storage alloy with CO-containing H_2. Temperature-programmed desorption (TPD) measurements on the pristine alloy and the corresponding one after hydrogen absorption-desorption cycles exhibit that: (1) the molecular CO can be adsorbed on the clean alloy surface and thus decrease the hydrogen storage ability of the alloy; (2) with the increase of the cycle number the partial decomposition of the CO and the subsequent adsorption of C atom and O atom on the surface is deleterious to the hydrogen storage competence of alloy. From the results of first-principle calculations, it is found that the adsorption of the molecular CO prefers the on-top and bridging sites on the Ni atoms. Moreover, the latter one is more stable than the former one.