Experimental investigation of charge transfer coefficient and exchange current density in standard fuel cell model for polymer electrolyte membrane fuel cells

Two representative parameters, exchange current density (j(0)) and charge transfer coefficient (alpha), in a standard fuel cell model of polymer electrolyte membrane fuel cells (PEMFCs) were experimentally investigated. The polarization characteristics and the corresponding electrochemical impedance spectra of the normal PEMFCs were measured and Tafel curves were calculated from them, where j(0) and. were finally calculated. As a result, the calculated j(0) was 0.11-0.70 A/cm(2), while the. was 0.056-0.023, depending on the operating temperature. Here, the j(0) is extremely overestimated while. is underestimated as compared with those in literature. Although the reason for such difference is not clear, it is expected that it could affect the predicted performance by the model significantly if the fuel cell performance is improved highly in the future so the activation overvoltage corresponding to identical current is lowered.