Reliability and accuracy of measured overpotential in a three-electrode fuel cell system

Numerical simulation was conducted to study the potential and current densi ty distributions at the active electrode surface of a solid oxide fuel cell . The effects of electrode deviation, electrolyte thickness and electrode p olarization resistance on the measurement error were investigated. For a co axial anode/electrolyte/cathode system where the radius of the anode is gre ater than that of cathode, the cathode overpotential is overestimated while the anode overpotential is underestimated. Although the current interrupti on method or impedance spectroscopy can be employed to compensate/correct t he error for a symmetric electrode configuration, it is not useful when dea ling with the asymmetric electrode system. For the purpose of characterizin g the respective overpotentials in a fuel cell, the cell configuration has to be carefully designed to minimize the measurement error, in particular t he selection of the electrolyte thickness, which may cause significant erro r. For the anode-support single fuel cell, it is difficult to distinguish t he polarization between the anode and cathode with reference to a reference electrode. However, numerical results can offer an approximate idea about the source/cause of the measurement error and provide design criteria for t he fuel cell to improve the reliability and accuracy of the measurement tec hnique.