Application of Scanning Transmission Electron Microscopy in the Studies of Atomically Dispersed Catalysts

Aberration-corrected scanning transmission electron microscopy(STEM) has been widely used in the structural and compositional analysis of functional materials due to its atomic-level spatial resolution in imaging and spectroscopic analysis.In particular, STEM high-angle annular dark-field(STEM-HAADF) imaging has significant advantages in the structural analysis of supported metal catalysts by virtue of its atomic-number contrast(Z contrast) and electron channeling effect.Through STEM-HAADF imaging, the distribution of heavy noble metal atoms on light support materials can be directly visualized in real space with single-atom sensitivity, and statistical analysis of different surface species can also be obtained, which makes STEM-HAADF imaging the most important structural analysis technique for the studies of emerging single-atom catalysts(SACs).As complementary techniques to STEM-HAADF imaging, STEM-based X-ray energy dispersive spectroscopy(EDS) and electron energy loss spectroscopy(EELS) can directly probe chemical composition and/or valence states at the nanoscale or even the atomic scale.The combination of imaging and spectroscopy in STEM thus provides a comprehensive analysis of the catalyst structure from multiple perspectives.Furthermore, when combined with in-situ electron microscopy techniques, the structural evolution of the catalyst under simulated working environments can be explored on the temporal axis, helping to unveil the structural origins of the catalytic activity and the failure mechanism of the catalysts.This review article briefly introduces the application of aberration-corrected STEM in the research of atomically dispersed supported catalysts, and provides prospects for the future development of STEM techniques for catalysis research.