Particle size effect of hydrogen-induced lattice expansion of palladium nanoclusters

In situ synchrotron x-ray diffraction experiments on bare palladium nanoclusters prepared by inert-gas aggregation and size selected (1.7-6.0 nm) show significant changes in lattice parameter upon hydrogen loading and a narrowing of the miscibility gap, as the cluster size decreases. The results show that the miscibility gap is open for all cluster sizes studied, in contrast to previous literature results from surfactant-encapsulated palladium clusters. We interpret these results by showing that the nature of the surface is critical in the hydrogenation behavior of the nanoclusters.