Distribution of relaxation times used for analyzing the electrochemical impedance spectroscopy of polymer electrolyte membrane fuel cell

Abstract

In this paper, a 25 cm2 polymer electrolyte membrane single cell is prepared by ultrasonic spraying coating method. The polarization curves and Electrochemical Impedance Spectroscopies (EIS) data of this cell are collected under different conditions, such as cell temperature, humidity, back pressure and pure O2. EIS data are analyzed by Distribution of Relaxation Time (DRT), and some results are concluded: (i) with the increase of current density, the Oxygen Reduction Reaction (ORR) time constant became lower, and the ORR reaction resistance and oxygen diffusion resistance both increases. (ii) With the increase of back pressure, the DRT peak assigned to oxygen diffusion process in cathode moves to low frequencies, the peak area decreases simultaneously. (iii) the proportion of the ORR polarization resistance gradually increases from 77 % to 84 % with the cell temperature increase from 65 °C to 80 °C. (iv) With the increase of humidity, the performance of the cell is decreased. (v) The oxygen diffusion resistance is negligible in pure oxygen working condition analyzed by DRT method.