Electrochemical promotion of electronically isolated and dispersed Pt catalysts

Abstract

Abstract. In this paper we discuss the first attempts to induce the effect of Electrochemical Promotion or Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA) on highly dispersed catalyst-electrodes systems which can compete in terms of dispersion and surface area with industrial catalysts. Three systems are discussed: 1. Electrochemical promotion of CEH 4 oxidation on electronically isolated Pt catalysts on YEO3-stabilized-Zirconia (YSZ) where NEMCA is induced via potential application between two terminal Au electrodes also supported on the solid electrolyte (bipolar design). Electrochemical promotion of C2H4 oxidation on a finely dispersed Pt catalyst deposited on aAu electrode which is supported on YSZ. 3. Induction of NEMCA during CHaOH oxidation on Pt without external voltage application by utilizing the potential difference developed between the catalyst and a catalytically inert counter electrode. In all cases significant non faradaic behavior has been obtained. The underlying catalytic/electrocatalytic phenomena are discussed together with some of the engineering challenges for potential practical applications.

High Faradaic Yields of Non-Faradaic Electrochemical Modification of Catalytic Activity of Propane Oxidation at Pt-YSZ

“…The largest faradaic yield in this work is one of the highest values from propane oxidation at Pt-YSZ and probably second only to the work of Billard and Vernoux in which a value of 1.2 × 10 6was reported,20 while common values are generally in the orders of 10 2 -10 3 [16][17][18][19]21. Systems with wireless configurations rarely achieve faradaic yields beyond 10 3 [5][6][7]. On the other hand, the cell prepared by WI exhibited poorer performance.…”

“…According to the bipolar electrode concept proposed by Marwood et al, [5][6][7][8][9][10][11][12] the work function should be increased in one region and decreased in the other of each Pt particle on YSZ. As propane oxidation under similar conditions exhibits the electrophobic behavior, 15,[19][20][21][22][23] the reaction rates should be enhanced and suppressed, respectively, in those regions.…”

“…[16][17][18][19]21 Systems with wireless configurations rarely achieve faradaic yields beyond 10 3 . [5][6][7] On the other hand, the cell prepared by WI exhibited poorer performance. Its highest faradaic yield was obtained at 6 V and smaller than its counterpart by a factor of 5.…”

“…This configuration is termed 'wireless' due to the absence of the direct contact between the catalyst and the wire. 5,6 The exact mechanism of how NEMCA occurs in this configuration is still unclear but a limited number of NEMCA studies conducted in wireless configuration suggest that the catalyst clusters deposited on the electrolyte function as bipolar electrodes. [5][6][7][8][9][10][11][12] As wireless configurations do not require the catalyst layer to be in a single continuous phase of high electrical conductivity, a catalyst can be dispersed as fine particles on an ionic conductor for more effective use of precious metals.…”