Degradation mechanism study of stationary PEMFC under low humidity condition, and in situ diagnosis method using electrochemical impedance spectroscopy (EIS). 저습도 조건에서의 PEMFC 열화 원인 및 전기화학 분석법을 이용한 인시추 분석방법

Abstract

This work reports the degradation mechanism of a single Polymer electrolyte membrane fuel cell (PEMFC) under low humidity at a constant current of 300 mA cm-2 and development of in situ electrochemical diagnosis method. While operating at constant current for 600 h at a Relative Humidity (RH) 30% condition, degradation mechanism is clearly different; (i) ionomer degradation (ii) membrane thinning which is irreversible degradation of MEA, and (iii) reverse current decay inducing severe cathode deterioration. To understand the specific degradation mechanism under low humidity, the internal resistance of MEA with different cell voltage was systemically studied by measuring electrochemical impedance spectroscopy (EIS) at Relative Humidity (RH) of 30% condition. Among them, Nyquist plot at a cell voltage of 0.85 V under RH 30 % condition could make it possible to focus on the MEA itself by increasing the ionic resistance deliberately. Partially, electrochemical analysis results at RH 30 % condition showed enormous differences by comparison to those of RH 100 % condition during degradation processes. Each of electrochemical databases could facilitate more precise diagnosis about the deteriorated component of MEA. Furthermore, such analysis methodology could be used as a useful tool for a degradation mechanism study of PEMFC under diverse degradation condition in more detail for the future.