*Ciclo de Charlas del Departamento de Física* *"Oxygen conducting ceramics as attractive supports for heterogeneous catalysis"*
*Dra. Elena Baranova* **Department of Chemical and Biological Engineering Centre for Catalysis Research and Innovation (CCRI) University of Ottawa, Ottawa
***Martes 21/11. 16hs.* ***Sala de conferencias * ***(Av. Alem 1253 - Cuerpo B - Subsuelo) **
*Abstract*
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Solid ionic conductors such as yttria-stabilized zirconia (YSZ) and doped-ceria (Sm-CeO_2 or Gd-CeO_2 ) are widely used in the fuel cells, sensors and in heterogeneous catalysis, particularly in electrochemical promotion of catalysis (EPOC). For instance, yttria-stabilized zirconia (8%-Y_2 O_3 -ZrO_2 ) has attracted significant attention in the last decades due to its unique properties such as high ionic conductivity in the temperature range of 300 - 1000^o C due to the presence of oxygen vacancies, as well as chemical and mechanical stability. Ceria (CeO_2 ), a mixed ionic-electronic conducting (MIEC) material, conducts O^2- ions due to oxygen vacancies in the crystallographic structure and electrons. Additionally, because of its non-stoichiometry, CeO_2 has the ability to undergo conversion between Ce^4+ and Ce^3+ quite easily. In heterogeneous catalysis, this reducibility and presence of oxygen vacancies play a significant role in the enhancement of catalytic activity, usually referred to as metal-support interaction (MSI). Similarly, the phenomenon known as electrochemical promotion of catalysis (EPOC) or non-faradaic electrochemical modification of catalytic activity (NEMCA) has also been shown to alter catalytic activity by in-situ controlled migration of promoting species such as O^2- through the application of an electrical current or potential. EPOC and MSI have long been considered as two different phenomena, however, more recently it has been shown that, functionally, for ionic and MIEC materials, both are linked by the transfer of ionic species at the interfaces. The difference between the two phenomena has been shown to be only operational. It has been said that EPOC is electrochemically controlled MSI, likewise, MSI is considered as self-induced EPOC. First, the concept of MSI and EPOC phenomena and their origin will be presented, following by the discussion of EPOC and MSI at the RuO_2 , IrO_2 , Ni- and Pt-based nano-structured catalyst interfaced with YSZ and CeO_2 in the instance of complete ethylene and carbon monoxide oxidation as well as CO hydrogenation.
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