Characterization of Catalysts in an Aberration-Corrected Scanning Transmission Electron Microscope

Aberration-corrected scanning transmission electron microscopes (STEM) with a sub-angstrom resolution and outstanding analytical capabilities provide a superior means for the characterization of heterogeneous catalysts. Images can be recorded with bright field, annular dark field, and secondary electron detectors using various signals. This is demonstrated here for different model catalysts, including metal particles on ZrO2 and CeO2. While it is often difficult to detect metal nanoparticles with a diameter of 1 nm or below supported on strongly scattering crystalline oxides by conventional transmission electron microscopy, the combinations of information obtained with different detectors in a STEM may facilitate their visualization. Of particular importance is the combination of the images with the spectroscopic investigation of selected points and areas. Efficiently collected electron energy loss and X-ray spectra are often essential to identify the nanoparticles unambiguously.