Research Highlights 2014

Single Atoms in Catalysts

Z-contrast imaging on a Cs-corrected STEM allows one to achieve the visualization of single atoms which is often important to understand the behaviour of catalyst materials. The image shows the distribution of UO_x on a ZrO₂ support: U atoms are recognizable as brighter spots (encircled) . This is an alternative catalyst for the industrially important oxidation of HCl into the more valuable chlorine. For methane steam reforming, atomically dispersed Rh is reactive.

Structural Changes of a U₃O₈/ZrO₂ Catalyst During HCl Oxidation – a HAADF-STEM Study
F. Krumeich, A. P. Amrute, C. Mondelli, and J. Pérez-Ramírez
Z. anorg. allg. Chem. 640 (2014) 768–773, DOI

Structure, Activity, and Stability of Atomically Dispersed Rh in Methane Steam Reforming
R.B. Duarte, F. Krumeich, and J.A. van Bokhoven
ACS Catalysis 4 (2014) 1279−1286, DOI

Atomically dispersed rhodium on support: Influence of metal precursor and support
R.B. Duarte, O.V. Safonova, F. Krumeich, and J.A. van Bokhoven
PhysChemChemPhys 16 (2014) 26553-26560, DOI

Phase Contrast in STEM

Phase-contrast STEM imaging in an aberration-corrected microscope represents an increasingly important alternative to the well-established HRTEM method. In both methods, the image contrast is coherently generated and thus depends not only on illumination and collection angles but on defocus and specimen thickness as well. This can be understood on the basis of the reprocity principle as demonstrated in this review. The application of PC-STEM is demonstrated by the image of LiBC shown above that reveals the positions of all atoms in the graphite-related structure.

Phase-Contrast Imaging in Aberration-Corrected Scanning Transmission Electron Microscopy
F. Krumeich, E. Müller, and R. A. Wepf
Micron 49 (2013) 1-14 DOI

Characterization of LiBC by Phase-Contrast Scanning Transmission Electron Microscopy
F. Krumeich, M. Wörle, P. Reibisch, and R. Nesper
Micron 63 (2014) 64-68 DOI

Recent Research Highlights