Polarization Effects in Intermediate Temperature, Anode‐Supported Solid Oxide Fuel Cells

Abstract

Anode-supported solid oxide fuel cells with yttria-stabilized zirconia (YSZ) electrolyte, Sr-doped LaMnO 3 (LSM)ϩ YSZ cathode, and Ni ϩ YSZ anode were fabricated and their performance was evaluated between 650 and 800ЊC with humidified hydrogen as the fuel and air as the oxidant. Maximum power densities measured were ϳ1.8 W/cm 2 at 800ЊC and ϳ0.82 W/cm 2 at 650ЊC. Voltage (V) vs. current density (i) traces were nonlinear; V vs. i exhibited a concave-up curvature [d 2 V/di 2 Ն 0] at low values of i and a convex-up curvature [d 2 V/di 2 Յ 0] at higher values of i, typical of many low temperature fuel cells. Analysis of concentration polarization based on transport of gaseous species through porous electrodes, in part, is used to explain nonlinear V vs. i traces. The effects of activation polarization in the Tafel limit are also included. It is shown that in anode-supported cells, the initial concave-up curvature can be due either to activation or concentration polarization, or both. By contrast, in cathode-supported cells, the initial concave-up curvature is entirely due to activation polarization. From the experimentally observed V vs. i traces for anodesupported cells, effective binary diffusivity of gaseous species on the anodic side was estimated to be between ϳ0.1 cm 2 /s at 650ЊC and ϳ0.2 cm 2 /s at 800ЊC. The area specific resistance of the cell (ohmic part), varied between ϳ0.18 ⍀ cm 2 at 650ЊC and ϳ0.07 ⍀ cm 2 at 800ЊC with an activation energy of ϳ65 kJ/mol.

Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

“…Lab tests of single button cells in humidified hydrogen at 800 °C (Ni/YSZ|YSZ|LSCF) (This notation indicates the material composing the cell in the following order: Anode | Electrolyte | Cathode.) have demonstrated power densities up to 1.8 W/cm 2 at 800 C [11,12]. In comparison, the power density per unit area for 2 kW planar anode-supported SOFC stacks (Ni/YSZ|YSZ|LSM) operated on reformate H 2 is estimated to be between 0.3 and 0.4 W/cm 2 [1].…”

High Temperature Fuel Cell

“…However, for such a configuration, the major technical challenge involves fabricating a dense and gas-tight YSZ electrolyte layer of thickness 50 µm or less supported on a porous NiO-YSZ (anode) substrate. Several studies describe the performance of such anode-supported SOFC (Basu et al, 2005;Kim et al, 1999;Yoon et al, 2007 …”

Effects of fuel processing methods on industrial scale biogas-fuelled solid oxide fuel cell system for operating in wastewater treatment plants

“…The modeling of polarizations used in the computer code has been described in Refs. [38][39][40]. The inlet and outlet fuel streams from the anode were assumed to be in thermodynamic equilibrium in the cell modeling…”