Solubility of hydrogen in single-sized palladium clusters - art. no. 075408

Hydrogen concentration-pressure isotherms of surfactant-stabilized palladiu m clusters and polymer-embedded palladium clusters with diameters of 2, 3, and 5 nm are measured with the gas sorption method at room temperature. The results show that, compared to bulk palladium, the hydrogen solubility in the a phase of the clusters is enhanced fivefold to tenfold, and the miscib ility gap is narrowed. Both results can be explained by assuming that hydro gen occupies the subsurface sites of the palladium clusters. The Pd-H isoth erms of all clusters show the existence of hysteresis, even though the form ation of misfit dislocations is unfavorable in small clusters. Compared to surfactant-stabilized clusters, the polymer-embedded clusters show slow abs orption and desorption kinetics. The absorption kinetics can be described b y a diffusion model for the composite polymer-cluster system.