The effect of O2 preadsorption on the rate of H2 absorption on the surface of rare earths (La, Ce, Tb, Dy) at 298 K

Abstract The reactivities of H 2 and O 2 with La, Ce, Tb and Dy were measured at 298 K under UHV condition. The reactivity of H 2 with these rare earths was very high and decreased with increasing coverage of the dihydride phase on the surface. As hydriding proceeds, a drastic change in the color of the rare earths was observed, indicating the change in the feature from metal to nonmetal of the hydrides. The O 2 reactivity was quite different for various rare earths. The oxidized Ce surface exhibits the highest H 2 reactivity in comparison with the other rare earth oxides.