Some contributions of electron microscopy to the characterisation of the strong metal-support interaction effect

The contribution of electron microscopy techniques to establishing the existence and actual nature of the metal-support interaction effects occurring in a variety of supported metal catalysts is reviewed. Data pertaining to systems based on both classic reducible supports like TiO2, CeO2 or some ceria-based mixed oxides, and several others generally considered as non-reducible oxides, like La2O3 or SiO2, are presented and discussed. The specific temperature and chemical conditions under which strong metal-support interaction phenomena are onset or reverted in each case are also analysed. The whole set of data presented and discussed here clearly shows that the electron microscopy techniques have made an outstanding contribution to the characterisation of the strong metal/support interaction effects exhibited by different metal/oxide systems. Likewise, it is demonstrated that this powerful family of techniques has very much helped to discriminating between true SMSI-like phenomena, as originally defined by Tauster et al., and several other apparent effects which, though at a first sight show some of the chemical, nano-structural and/or catalytic characteristics of the SMSI effect, have a neatly different origin. (C) 2002 Elsevier Science B.V. All rights reserved.