Electrochemical performance and impedance of a conical pore in the low–Pt PEM fuel cell catalyst layer

Abstract

A model for the transient electrochemical performance of a conical pore in the cathode catalyst layer of a low–Pt PEM fuel cell is developed. The pore is separated from the Pt surface by a thin ionomer film. A transient equation for the oxygen diffusion along the pore coupled to the proton conservation equation in the ionomer film is derived. Numerical solution of the static equations shows superior electrochemical performance of a conical pore as compared to cylindrical pore with equivalent electrochemically active surface area. Equations for the pore impedance are derived by linearization and Fourier–transform of transient equations. The conical pore impedance is calculated and compared to the impedance of equivalent cylindrical pore. It is shown that the pore shape affects the frequency dependence of impedance.