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

       Solid ionic conductors such as yttria-stabilized zirconia (YSZ) and doped-ceria (Sm-CeO₂ or Gd-CeO₂) 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%-Y₂O₃-ZrO₂) 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^oC due to the presence of oxygen vacancies, as well as chemical and mechanical stability. Ceria (CeO₂), 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, CeO₂ has the ability to undergo conversion between Ce⁴⁺ and Ce³⁺ 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 RuO₂, IrO₂, Ni- and Pt-based nano-structured catalyst interfaced with YSZ and CeO₂ in the instance of complete ethylene and carbon monoxide oxidation as well as CO hydrogenation.