Relaxation time distribution analysis of a polymer electrolyte fuel cell stack ...

• Author(s): Lopes, Vitor V. ; Silva, R. A. ; Novais, Augusto Q. ; Rangel, C. M.
• Date: 2011
• Persistent ID: http://hdl.handle.net/10400.9/1468
• Origin: Repositório do LNEG
• Subject(s): Distribution of relaxation times; Electrochemical impedance spectroscopy; Proton exchange membrane fuel cell
• Document Type: Conference Object
• Language: English

Description

Electrochemical impedance spectroscopy (EIS) is an analysis technique that is commonly used as a base diagnostics technique for the in-situ analysis of the kinetic and transport properties of proton exchange membrane (PEM) fuel cells. This work proposes to use the distribution of relaxation times (DRT) as a complementary analysis technique for the interpretation of EIS data. For this purpose, the DRT is deduced for a modified Randles electric circuit composed of a constant phase element (CPE) connected in parallel with a resistance in series with a finite diffusion Warburg element. The experimental EIS data collected from an eight cell PEMFC with an open-air cathode was modeled through the use of two modified Randles circuit representing the fuel-cell electrodes. The analysis of the DRT allows to identify further characteristics of the individual processes that occur at both electrodes, while also being instrumental in detecting the effect on the fuel cell performance of some operating conditions, namely hydrogen flow-rate and current.