Hydrogenation kinetics and surface compositions of ErT 2 systems (T ≡ Mn, Fe, Co, Ni)

Abstract

The kinetics of absorption of hydrogen by intermetallic compounds is an important factor with regard to the use of these materials for hydrogen storage. The results of previous work in the field have suggested that the kinetics of absorption of hydrogen are more rapid for manganese and iron intermetallic compounds than for cobalt- and nickel-containing systems. To ascertain whether this trend is indeed correct, hydrogen absorption kinetic studies were performed on the intermetallic series ErT 2 with T ≡ Mn, Fe, Co, Ni. The rate of absorption follows the trend ErMn 2 > ErFe 2 > ErCo 2 > ErNi 2 with the rates differing by about a factor of 500. The kinetics results are correlated with the observed surface compositions determined by Auger electron spectroscopy. The surface enrichment by the d transition metal is greatest for ErMn 2 and least for ErNi 2, but the difference is insufficient to account for the variation in kinetic behavior.