ADF-STEM Imaging of Nascent Phases and Extended Disorder Within the Mo–V–Nb–Te–O Catalyst System
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Materials investigated for their potential use as heterogeneous selective oxidation catalysts may sometimes show highly ordered regions at the nanoscale which are embedded within highly disordered matrices from which they nucleate. These are often referred to as X-ray amorphous due to the lack of higher-order Bragg reflections; however, here we use annular dark-field scanning transmission electron microscopy (ADF-STEM) real space imaging to characterize the local structure of nanometer size domains of compositionally and structurally complex nascent oxide phases present in multi-phase disordered solids. These images have been obtained using aberration-corrected scanning transmission electron microscopy and point to its potential for local structural characterization where the synthesis conditions for a particular phase are not optimized or where self-assembly to extended structures has been locally hindered. Such studies may lead to identification of new catalysts, provided their targeted synthesis can be scaled up.
KeywordsADF-STEM Selective oxidation Oxidative dehydrogenation
T.V. and D.A.B. thank the VPR of the University of South Carolina for financial support of the JEOL 2100F facility. The research at Oxford University leading to results shown here has been funded by the European Union Seventh Framework Programme under Grant Agreement 312483–ESTEEM2 (Integrated Infrastructure Initiative–I3) and EPSRC Grant Code, EP/K040375/1, for the ‘South of England Analytical Electron Microscope’.
- 6.DeSanto P, Buttrey DJ, Grasselli RK, Lugmair CG, Volpe AF, Toby BH, Vogt T (2004) Structural aspects of the M1 and M2 phases in MoVNbTeO propane ammoxidation catalysts. Z Krist 219:152–165Google Scholar
- 10.Sadakane M, Yamagata K, Kodato K, Endo K, Toriumi K, Ozawa Y, Ozeki T, Nagai T, Matsui Y, Sakaguchi N, Pyrz WD, Buttrey DJ, Blom, DA, Vogt T, Ueda W (2009) Synthesis of orthorhombic Mo-V-Sb oxide species by assembly of pentagonal Mo6O21 polyoxometalate building blocks. Angew Chem Int Ed 48:3782–3786CrossRefGoogle Scholar
- 24.Wang ZW, Li ZY, Park SJ, Abdela A, Tang D, Palmer RE (2011) Quantitative Z-contrast imaging in the scanning transmission electron microscope with size-selected clusters. Phys Rev B 84:073408-1–073408-3Google Scholar