S. Gultekin et al., UNSTEADY-STATE PERFORMANCE OF POROUS GAS-DIFFUSION NI-ELECTRODE IN ALKALINE FUEL-CELLS, Arabian journal for science and engineering, 17(4A), 1992, pp. 465-474
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 c
ases where the electrochemical system does not come to equilibrium. Se
condly, most steady state methods employ impedance techniques. These i
mpedance methods, however, are known to give only overall values. Some
of the intrinsic parameters of the electrode (such as the exchange cu
rrent density and capacitance) can also be obtained from unsteady-stat
e techniques. In this study, an unsteady state technique in the form o
f exponential decay current was put in a galvanostatic mode and used t
o determine the exchange current density and double layer capacitance
of the hydrogen porous gas diffusion electrodes of the alkaline fuel c
ell. In addition, the effects of temperature on the determined paramet
ers are discussed. In order to compare the results (using the same exp
erimental conditions), a triangular wave current also in a galvanostat
ic mode was employed in a separate investigation. The ranges of values
obtained for the exchange current density and the double layer capaci
tance are (1.1-11.9) X 10(-6) A/cm2 and (91-104) X 10(-3)F, respective
ly, for the temperature range of 30-70-degrees-C. The activation energ
y was found to be 4.15 kcal/gmol and the surface roughness factor at 7
0-degrees-C was 34 x 10(-4) cm2/cm2, for Raney Ni-electrocatalyst.