Nanoparticulate Pt-Catalyzed Hydrogenation of Yb Films: Towards Hydrides with Higher Hydrogen Compositions

Abstract It is much more difficult to synthesize β-phase ytterbium trihydride (β -YbH3-δ) under moderate conditions than other rare-earth metal trihydrides because it requires a valence change from a fully occupied 4 f shell ( 4 f 14 ) in Yb2+ to an unclosed shell ( 4 f 13 ) in Yb3+. We synthesized β -YbH3-δ at ambient pressure through hydrogenation of a Yb film capped with platinum (Pt) nanoparticle (NP) catalysts. In addition, Pt NP capping enabled us to synthesize α -phase Yb dihydride (α -YbH2± δ) at room temperature. The difficulty of trihydrogenating Yb to β -YbH3- δ is explained by kinetic analyses based on temperature and time dependences of molar fractions of α-YbH2± δ and β -YbH3- δ . Pt NP capping can be used to synthesize other hydrogen-rich rare-earth metal hydrides under ambient pressure and lower temperatures.