Improved Catalytic Reactor for the Electrochemical Promotion of Highly Dispersed Ru Nanoparticles with CeO 2 Support

Electrochemical promotion of catalysis (EPOC) is a promising method for enhancing catalytic activity through the application of a small electrical stimulus between the catalyst-working and counter electrode deposited on a solid electrolyte 1 . The electronic properties of the catalyst can be modified resulting in a change in catalytic activity. In the case of yttria-stabilized zirconia (YSZ) as a solid electrolyte, the addition or removal of O 2- species on the catalyst surface can be controlled in situ depending on the specified reaction conditions. Fully reversible and “permanent” or “persistent” EPOC has been reported for more than 70 various catalytic systems 1 . In reversible EPOC experiments, the reaction rate returns to its initial value after the electrical stimulus is interrupted. For permanent EPOC (P-EPOC), the reaction rate remains at a higher value than the initial open circuit value 2,3 . Despite receiving much attention, this phenomenon has not yet reached commercial application. One of the main technical factors preventing such development is the use of thick film catalysts with low surface areas and high material costs 4 . Ceria, CeO 2 , is a mixed ionic-electronic conducting (MIEC) material that conducts O 2- due to oxygen vacancies in the crystallographic structure in addition to conducting electrons at elevated temperatures. Furthermore, due to its non-stoichiometry, CeO 2 has the ability to undergo conversion between Ce 4+ and Ce 3+ quite easily 5 . These properties make the use of ceria-containing catalysts of interest for many applications. In heterogeneous catalysis, Pt group metals deposited on CeO 2 show a metal-support interaction (MSI) effect associated with charge transfer between the two solids that are in contact. In EPOC studies, using a MIEC can also ensure electrical connectivity between highly dispersed nanoparticle catalysts 6 . In this study, electrochemical enhancement of catalytic activity of a low particle size (1.9 nm) ruthenium nanoparticles catalyst for ethylene oxidation was investigated. Ru nanoparticles, synthesized using a modified polyol reduction method, were supported on CeO 2 resulting in a 1 wt% Ru loading (RuNPs/CeO 2 ) (i.e., typical in heterogeneous catalysis studies).The highly dispersed RuNPs/CeO 2 catalyst powder was supported on a YSZ solid electrolyte in order to apply polarization. The discussion of this study includes the effect of the partial pressure of ethylene with constant partial pressure