Effect of Anodic Concentration Overvoltage on Power Generation Characteristics of Solid Oxide Fuel Cells

Abstract

Current‐voltage (I‐V) and anodic polarization characteristics were measured for the ‐fueled solid oxide fuel cell with an 8 mole percent yttria‐stabilized zirconia (YSZ) electrolyte and Ni‐YSZ anode. For a ‐rich system, the I‐V curve was characterized by a high open‐circuit voltage and significant concave bending in the small current density region. For an extremely dilute fuel condition, the curve started from a straight decrease of the voltage followed by a sharp voltage drop due to limiting current. Significant contribution of concentration overvoltage was suggested in determining the shape of the I‐V curve from the calculated equilibrium in the fuel systems. The experimentally obtained anodic polarization curve could be fitted to the calculated curve based on the concentration difference across the Ni‐YSZ anode layer. The effective diffusion coefficient, Deff, of the Ni‐YSZ cermet which affects the anodic polarization, is estimated to be . The electrode polarization conductivity, σa, was maximum at , and decreased with increasing or decreasing . This behavior could be explained by considering the concentration overvoltage based on the relation between log and the fractional concentration of .