Possible Misidentification of Heteroatom Species in Scanning Transmission Electron Microscopy Imaging of Zeolites
KAUST DepartmentAdvanced Membranes and Porous Materials Research Center
Physical Science and Engineering (PSE) Division
Chemical Science Program
KAUST Grant NumberFCC/1/1972-43-01
Embargo End Date2022-08-24
Permanent link to this recordhttp://hdl.handle.net/10754/670759
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AbstractAtomic-resolution scanning transmission electron microscopy (STEM) can be used to determine the location and state of heteroatom species in zeolites, which is essential for understanding their catalytic behavior. However, because of the complexity of zeolite structures and low heteroatom content, STEM images must be carefully interpreted to avoid misidentification. In this work, Fe-doped silicalite-1 was used as an example to illustrate this problem by combining STEM image simulation and experiments. Simulation results indicated that, unless the specimen has only one unit cell thickness, it is impossible to reliably identify Fe atoms in a zeolite framework using high-angle annular dark-field STEM (HAADF-STEM). Experimental HAADF-STEM images could not distinguish Fe-doped silicalite-1 and Fe-free silicalite-1 samples, thus confirming the infeasibility of using HAADF-STEM to determine the preferential occupancy of Fe between different crystallographic sites. It was also found that integrated differential phase contrast STEM (iDPC-STEM) could detect extraframework Fe species located in microporous channels only when the physically adsorbed volatile organic compounds were properly removed before imaging. The findings of this investigation provide important precautions and guidance for related research work.
CitationLiu, D., Liu, L., Wu, K., Zhou, J., Cheng, Q., Lv, J., … Han, Y. (2021). Possible Misidentification of Heteroatom Species in Scanning Transmission Electron Microscopy Imaging of Zeolites. The Journal of Physical Chemistry C. doi:10.1021/acs.jpcc.1c05516
SponsorsThis research is supported by the AMPM CCF fund (FCC/1/1972-43-01) to Y.H. from King Abdullah University of Science and Technology and the research grant to F.L. from the National Natural Science Foundation of China (No. 61971201).
PublisherAmerican Chemical Society (ACS)