The Overpotential of Nickel/Yttria-Stabilized Zirconia Cermet Anodes Used in Solid Oxide Fuel Cells

Abstract

The overpotential of Ni/yttria‐stabilized zirconia cermet anodes used in solid oxide fuel cells (SOFCs) was studied. We measured the current‐density dependence of the anodic overpotential at 85°C operating temperature using the inlet fuel gases with compositions of , , and . It was found that the overpotential was lower under wet‐anode conditions than under dry conditions. We also showed that under wet‐anode conditions the overpotential gradually increased with the increase of the current density, whereas under dry‐anode conditions, the overpotential increased steeply with the increase of the current density up to and then showed a gradual increase with the current density. We related the overpotential of SOFCs to the reaction rate constants and to the operating conditions by using a reaction model and found that the surface reaction model can successfully explain the experimental results. © 2000 The Electrochemical Society. All rights reserved.