Unexpected large hydrogen adsorption by Nb cluster films under mild conditions of pressure and temperature

Hydrogen absorption in several cluster assembled films was investigated by the optical and electrical response of the films when modified by hydrogen adsorption. The films were grown by deposition of niobium clusters and by co-deposition of niobium clusters with manganese or palladium clusters on sapphire and then capped by a thin Pd film. Unusual high adsorption of hydrogen by Nb clusters and thin metal oxide reductions at room temperature can be inferred by changes in optical transmission and resistance of the film. On the other hand, no hydrogen absorption can be inferred in the same experiments with co-deposited clusters of Nb and Pd and co-deposited clusters of Nb and Mn. The technique used in this work allows fast screening and detection of potential perm-selective materials for hydrogen.