Characterization and fault diagnosis of PAFC cathode by EIS technique and a novel mathematical model approach

Considerable ongoing research exists in the area of fuel cells for power and distributed power generation. Of the various types of fuel cells, phosphoric acid fuel cell (PAFC) is a mature technology and is under limited production in various parts of the world. Electrochemical impedance spectroscopy (EIS) is a powerful tool which can be used for characterization of PAFC cathodes. In EIS, the electrode response is analyzed against an equivalent electrical circuit for diagnostics. A shortcoming of this approach is that multiple circuits can match the same response and correlating the physical electrode parameters with the circuit components may become quite difficult. To avoid this, a mathematical model of the PAFC cathode that is easy to solve is developed. The relative value and position of the maximum phase angle with respect to frequency is proposed as a diagnostic marker. A diagnostics table based on this marker is developed using the simulation of the mathematical model and the results are experimentally verified.