Elucidating the Structure and Composition of Individual Bimetallic Nanoparticles in Supported Catalysts by Atom Probe Tomography

Understanding andcontrolling the structure and composition ofnanoparticles in supported metal catalysts are crucial to improvechemical processes. For this, atom probe tomography (APT) is a uniquetool, as it allows for spatially resolved three-dimensional chemicalimaging of materials with sub-nanometer resolution. However, thusfar APT has not been applied for mesoporous oxide-supported metalcatalyst materials, due to the size and number of pores resultingin sample fracture during experiments. To overcome these issues, wedeveloped a high-pressure resin impregnation strategy and showcasedthe applicability to high-porous supported Pd-Ni-based catalystmaterials, which are active in CO2 hydrogenation. Withinthe reconstructed volume of 3 x 10(5) nm(3), we identified over 400 Pd-Ni clusters, with compositionsranging from 0 to 16 atom % Pd and a size distribution of 2.6 & PLUSMN;1.6 nm. These results illustrate that APT is capable of quantitativelyassessing the size, composition, and metal distribution for a largenumber of nanoparticles at the sub-nm scale in industrial catalysts.Furthermore, we showcase that metal segregation occurred predominatelybetween nanoparticles, shedding light on the mechanism of metal segregation.We envision that the presented methodology expands the capabilitiesof APT to investigate porous functional nanomaterials, including butnot limited to solid catalysts.