Impedance of the hydrogen polymer fuel cell electrode. Theory and experiments

We derive the impedance for the hydrogen electrode in the polymer membrane fuel cell from irreversible thermodynamics. The results predict a surface c ontribution to the cell impedance that can give two semi-circles in the Nyq uist diagram. The equivalent circuit of the impedance is shown. The high-fr equency contribution is connected to the oscillation of dipoles consisting of free charges in the surface, while the low-frequency contribution is con nected to the electrochemical reaction. This can be explained by a slowly r elaxing proton conducting polymer network at the reaction site.