Unsteady state performance of porous gas-diffusion electrodes in alkaline fuel cell

Abstract EN

The traditional approach of using steady-state techniques to determine the performance of the electrodes of fuel cells may have two main set-backs.

Firstly, steady state techniques are not suitable for use in cases where the electrochemical system does not come to equilibrium.

Secondly, most steady state methods employ impedance techniques.

These impedance methods, however, are known to give only overall values.

Some of the intrinsic parameters of the electrode (such as the exchange current density and capacitance) can also be obtained from unsteady- state techniques.

In this study, an unsteady state technique in the form of exponential decay current was put in a galvanostatic mode and used to determine the exchange current density and double layer capacitance of the hydrogen porous gas diffusion electrodes of the alkaline fuel cell.

In addition, the effects of temperature on the determined parameters are discussed.

In order to compare the results (using the same experimental conditions), a triangular wave current also in a galvanostatic mode was employed in a separate investigation.

The ranges of values obtained for ،the exchange current density and the double layer capacitance are (1.1 *(9.لل-ل(T6 A/cm2 and (91-104)X 10“3F, respectively, for the tempera- ture range of 30-70°C.

The activation energy was found to be 4.15 kcal/gmol and the surface roughness factor at 70°c was 34xl0~‘،cm2/cm2, for Raney Ni- electrocatalyst.