Microstructure and composition of hybrid Pd-Nafion membranes

► Metallic Pd and Pd hydride nanocrystallites coexist in the Pd-Nafion membranes. ► Amorphous Pd oxides exist in the Pd-Nafion membranes. ► Pd particles have complicated three dimensional structure. ► We proposed a three dimensional structure model of Pd-Nafion membranes.