Degradation of a polymer exchange membrane fuel cell stack with Nafion® membranes of different thicknesses: Part I. In situ diagnosis

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. The durability of polymer exchange membrane (PEM) fuel cells, under a wide range of operational conditions, has been attracting intensive attention, as durability is one of the largest barriers for commercialization of this promising technology. In the present work, membrane electrode assembly (MEA) degradation of a four-cell stack with Nafion membranes of different thicknesses, including N117, N115, NR212, and NR211, was carried out for 1000 h under idle conditions. By means of several on-line electrochemical measurements, the performance of the individual cells was analyzed at different times during the degradation process. The results indicate that the cells with thinner membranes have a lower open circuit voltage (OCV) due to the higher fuel crossover. Before degradation, the thickness of the membranes correlates with performance of the cell. However, with the advancement of degradation, the performance of cells with thinner membranes degraded much faster than those with thicker membranes, especially after 800 h of operation. The fast performance degradation for thinner membranes is evident by a dramatic increase in hydrogen crossover indicating membrane thinning or pinhole formation. Crown

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

“…Many attempts were made in the past few years to develop more robust components and operational regimes capable of withstanding harsh fuel cell conditions against degradation. In [54] the design of membranes was suggested to be made thicker to reduce hydrogen crossover to the cathode. According to [55], sulfonated polymidie membranes exhibit better stability than Nafion under electric load cycling.…”

Degradation of a PEM fuel cell stack with Nafion® membranes of different thicknesses. Part II: Ex situ diagnosis

“…The fuel cell stack temperature was kept at 70 • C, and air and hydrogen were fully humidified prior to their delivery into the fuel cell. Detailed procedures of this stack degradation test, as well as electrochemical measurements, have been described in the literature [7].…”

“…IR imaging and gas permeability measurements were performed before cutting the samples for SEM and contact angle observations. The "fresh" samples were the ones that have been compressed and conditioned without any further operation as described in our previous publication [7].…”

“…Wu et al [6] conducted a six-cell stack degradation procedure under close to open circuit voltage (OCV) conditions, finding considerable hydrogen crossover after 800 h of operation. To facilitate membrane degradation studies, Yuan et al [7] reported an accelerated degradation test involving a four-cell stack degradation procedure using Nafion membranes of different thicknesses, including N117, N115, NR212, and NR211, for 1000 h under idle conditions. The cell performance and electrochemical characteristics were monitored approximately every 200 h of operation.…”

“…Previously, we performed an in situ diagnosis of a four-cell stack with membranes of different thicknesses, where traditional electrochemical diagnostic tools (including OCV, polarization curve, electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV)) were used to observe performance losses after 1000 h of operation under idle conditions [7]. In the present work, an ex situ diagnosis is carried out to identify the major failure mode.…”