Stability and Performance of YSZ Infiltrated Platinum Electrodes for Sensors and Solid Oxide Cells
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Stability and Performance of YSZ Infiltrated Platinum Electrodes for Sensors and Solid Oxide Cells Aligul Buyukaksoy1, Vladimir Petrovsky1 and Fatih Dogan1 1 Missouri University of Science and Technology, Department of Materials Science & Engineering, 223 McNutt Hall, 1400 N. Bishop Rolla, MO 65409-0340506 ABSTRACT Limited electrochemical performance and microstructure instability are crucial problems in Platinum electrodes for solid state electrochemical devices. YSZ infiltration into porous YSZ skeleton is a prospective method to enhance the electrochemical performance and stabilize the microstructure. In this work, the effect of Pt skeleton microstructure on the electrochemical performance and stability of Pt-YSZ electrodes prepared by infiltration was investigated. The electrode polarization resistance of YSZ infiltrated Pt electrode sintered at 800 °C was 0.060 Ohm.cm2 per electrode at 800 °C without degradation during the operation time of 51 hours. Triple phase boundary enhancement by YSZ infiltration and YSZ infiltration into Pt skeleton with smaller particle size resulted in the suppression of the electrochemical process observed at 150 Hz. INTRODUCTION Platinum is widely used as electrode materials in solid oxide fuel cells (SOFCs); solid oxide electrolysis cells (SOECs) and gas sensors [1, 2]. Pt exhibits pure electronic conductivity (i.e. no bulk ionic conductivity). Therefore, the oxygen reduction reaction is confined to the triple phase boundaries (TPBs) where the electronic conductor (Pt), ionic conductor (YSZ electrolyte) and the gas phase meet. Pt-YSZ composite electrodes have been used to obtain maximized TPB length and consequently minimized polarization resistances [3-8]. It has been reported that it was possible to reduce electrode polarization resistances to 0.4 Ohm.cm2 per cathode at 900 °C from Pt-YSZ electrodes prepared by co-sintering Pt and YSZ powders. The performance of Pt-YSZ electrodes prepared by this method was shown to be strongly composition dependent [6, 7]. The introduction of the YSZ phase also resulted in inhibition of Pt particle coarsening, hence TPB length loss [3, 8]. However, since YSZ particles replace Pt particles in the Pt-YSZ composite case, the stabilization of the Pt electrode is realized at the expense of electrical conductivity. Infiltration of the electronically conductive phase into porous YSZ skeletons has been reported as a prospective route for electrode fabrication. It has been shown that efficient electrodes with relatively good stability were fabricated by this method [9-13]. In another study, our group has reported fabrication of Pt-YSZ electrodes by YSZ infiltration into porous Pt skeletons [14]. It has been demonstrated that the initial electrode polarization resistance of Pt electrode sintered at 800 °C improved from 0.1 Ohm.cm2 to 0.045 Ohm.cm2 at 800 °C when the sintering temperature is reduced to 600 °C and the obtained skeleton is infiltrated with YSZ. The objective of this study is to determine the effect of the initial particle size of Pt skeleton
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