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Catalysis Letters, Vol.143, No.11, 1085-1097, 2013
Promotion, Electrochemical Promotion and Metal-Support Interactions: Their Common Features
The catalytic activity and selectivity of metals can be significantly modified via the action of promoters, via the interaction with the support (metal-support interactions, MSI) or, when the support has some ionic mobility, via the application of electrical potential (+/- 2 V) between the catalyst and the support, a phenomenon known as electrochemical promotion of catalysis (EPOC). During the last two decades it is becoming increasingly obvious that chemical (classical) promotion, EPOC and MSI are, via the action of spillover of promoting species, very closely related, to the point that the differences between them are only operational and not functional. This impressive similarity is apparently closely related to the gradual substitution of classical insulating supports (SiO2, Al2O3) with ionically conducting or mixed ionically-electronically conducting ceramic supports in many commercial catalysts during the last 25 years. In this perspective we focus on a few key experiments which have demonstrated this striking similarity and we also discuss some recent advances on the electrochemical promotion of finely dispersed catalysts which appear to be of significant practical interest.
Keywords:Promotion;Electrochemical promotion of catalysis (EPOC);Non-Faradaic electrochemical promotion of catalysis (NEMCA effect);Metal-support interactions (MSI);Catalytic nanodiode;Spillover-backspillover phenomena;Fermi level;Work function;Double layer