Quantitative Z‐Contrast Imaging of Supported Metal Complexes and Clusters—A Gateway to Understanding Catalysis on the Atomic Scale

Abstract

AbstractZ‐contrast imaging in an aberration‐corrected scanning transmission electron microscope can be used to observe and quantify the sizes, shapes, and compositions of the metal frames in supported mono‐, bi‐, and multimetallic metal clusters and can even detect the metal atoms in single‐metal‐atom complexes, as well as providing direct structural information characterizing the metal–support interface. Herein, we assess the major experimental challenges associated with obtaining atomic resolution Z‐contrast images of the materials that are highly beam‐sensitive, that is, the clusters readily migrate and sinter on support surfaces, and the support itself can drastically change in structure if the experiment is not properly controlled. Calibrated and quantified Z‐contrast images are used in conjunction with ex situ analytical measurements and larger‐scale characterization methods such as extended X‐ray absorption fine structure spectroscopy to generate an atomic‐scale understanding of supported catalysts and their function. Examples of the application of these methods include the characterization of a wide range of sizes and compositions of supported clusters, primarily those incorporating Ir, Os, and Au, on highly crystalline supports (zeolites and MgO).