H concentrations and stresses in Pd nanoparticles

•Surface segregation and surface stress of nanoparticles.•H-trap depth of Pd surface, H concentrations and stresses in both core and surface shell of Pd nanoparticles.•Coupling between the stresses and H concentrations in the surface shell and core of the Pd nanoparticles.•H concentrations in the core and surface shell generating tensile hydrostatic stress in the core.•The tensile hydrostatic stress in the core enhancing the H concentration in the core.

Using the Gibbs-approach based adsorption isotherm and the experimental data of nominal H concentration in Pd nanoparticles with a mean diameter of 3.6 nm versus H2 partial pressure, we determined the H-trap depth of Pd surface, the H concentrations and stresses in both core and surface shell of the nanoparticles. The results indicate that in addition to the surface segregation of H atoms, the tensile hydrostatic stress induced by the difference in concentration between the core and the surface shell greatly enhances the H concentration in the crystalline core in comparison with that in the bulk Pd counterpart under the same H2 partial pressure.