Solid Oxide Fuel Cell with Nanostructured Fuel Electrode
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1023-JJ02-04
Solid Oxide Fuel Cell with Nanostructured Fuel Electrode Syed Asif Ansar, and Zeynep Ilhan German Aerospace Center, Stuttgart, 70560, Germany Abstract Nanostructured YSZ+NiO anodes (fuel electrode) for solid oxide fuel cell (SOFC) were developed by plasma spraying. Influence of processing parameters was correlated with deposit microstructure and properties. During particle in-flight with in the plasma jet, the high temperatures of plasma resulted in an increase in average crystallite size; the nanostructure was, however, conserved. Anodes with well distributed finely porous nanostructure exhibiting high gas permeability, suitable high temperature electronic conductivity, enhanced triple phase boundaries and catalytic activity were produced by controlling plasma enthalpy and velocity. Properties of nanostructured anodes were compared with conventional ones. At room temperature the permeability of nanostructured anodes was an order of magnitude higher than their conventional counter parts whereas in-plane conductivity at 800∞C in reducing atmosphere of former was 4% higher than that of the latter. Electrochemical performance of optimized nanostructured anode was compared with conventional NiO+YSZ anodes by testing full cells at 800∞C. 9.5 mol% YSZ electrolyte and LSM cathode were deposited onto these anodes for electrochemical testing in static and dynamic conditions. Impedance spectroscopy measurements were performed to collect data on polarization resistance and catalytic behavior of anode layers. Gas and temperature variation on both cells was performed and data was compared. It was established that enlarged reaction zone provided by high specific surface area of nanostructured anodes and finely porous microstructure led to lower activation and concentration polarizations and enhanced cell performance by more than 30% compared to conventional cells. During redox (oxidation and reduction of nickel in anode electrode) cycling the cell composed of nanostructured anode exhibited lower degradation. Introduction Solid oxide fuel cell (SOFC), an electrochemical device that converts energy of chemical reaction directly into electrical energy, has received a great deal of attention in recent years owing to its high efficiency, fuel flexibility and environmental friendliness [1]. Among the SOFC components, anode provides electrochemical reaction sites for oxidation of the fuel, allows transport of fuel and by products to or from the surface sites, and provides electronic conductive path for electrons to the interconnects. Porous Ni/YSZ cermet is currently the most common anode material for SOFC applications. Ni is an excellent reforming and electro catalyst for electrochemical oxidation of hydrogen and provides electronic conductivity. YSZ behaves as inhibitor for Ni coarsening and adjusts coefficient of thermal expansion of the anode closely to the electrolyte. This system is preferred because of its lower costs, chemical stability in reducing atmospheres at high temperatures and immiscibility of Ni in YSZ A v
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