The three-dimensional morphology of nickel nanodots in amorphous silica and their role in high-temperature permselectivity for hydrogen separation

We report the development of technologically important nickel (Ni) nanodots (nanoparticles) dispersed in amorphous silica (SiO₂) for high-temperature permselectivity for hydrogen separation membranes, crucial in hydrocarbon reactions and H₂ production, and present the systematic reconstruction of the three-dimensional (3D) structures of the nanodots using electron nano-tomography. 3D structures using cryogenic high-angle annular dark field scanning transmission electron microscopy (Cryo-HAADF-STEM), which is a more accurate method for nanoparticle morphology than conventional chemisorption, are correlated with experimental reversible hydrogen adsorption properties. The correlations provide the first direct evidence of very high activity on the nanoparticle surface and the nature of adsorption sites. The results have important implications in general for the use of electron nano-tomography in the design of supported metallic nanoparticles for hydrogen separation membranes.