Combined electrochemical and surface analysis investigation of degradation processes in polymer electrolyte membrane fuel cells

298

121

a b s t r a c tDurability is one of the major barriers to polymer electrolyte membrane fuel cells (PEMFCs) being accepted as a commercially viable product. It is therefore important to understand their degradation phenomena and analyze degradation mechanisms from the component level to the cell and stack level so that novel component materials can be developed and novel designs for cells/stacks can be achieved to mitigate insufficient fuel cell durability. It is generally impractical and costly to operate a fuel cell under its normal conditions for several thousand hours, so accelerated test methods are preferred to facilitate rapid learning about key durability issues. Based on the US Department of Energy (DOE) and US Fuel Cell Council (USFCC) accelerated test protocols, as well as degradation tests performed by researchers and published in the literature, we review degradation test protocols at both component and cell/stack levels (driving cycles), aiming to gather the available information on accelerated test methods and degradation test protocols for PEMFCs, and thereby provide practitioners with a useful toolbox to study durability issues. These protocols help prevent the prolonged test periods and high costs associated with real lifetime tests, assess the performance and durability of PEMFC components, and ensure that the generated data can be compared.Crown

Section: Gdl Degradationmentioning

confidence: 99%

A review of polymer electrolyte membrane fuel cell durability test protocols

Yuan

Zhang

et al. 2011

298

121

“…Water phase transition during 54 freeze-thaw cycles had no effect on GDL strain but an increase in in-plane and through-plane air permeability (18 and 80%, respectively) was found, which was attributed to material loss during permeability measurements as a consequence of weakened MPL structure under freezing conditions. Most recently, Schulze et al [13] found that the decomposition of PTFE in the electrodes induced a performance loss approximately twice as high as those related to the agglomeration of the platinum catalyst after 1000 h of fuel cell operation. However, the effect of PTFE degradation in the catalyst layer and GDL was not separated and the decomposition mechanism of PTFE was not thoroughly discussed in their paper.…”

Section: Introductionmentioning

confidence: 99%

In situ accelerated degradation of gas diffusion layer in proton exchange membrane fuel cellPart I: Effect of elevated temperature and flow rate

Martin

Orfino

et al. 2010

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. Past studies have shown that both the substrate and microporous layer of the gas diffusion layer (GDL) significantly affect water balance and performance of a proton exchange membrane (PEM) fuel cell. However, little effort has been made to investigate the importance of GDL properties on the durability of PEM fuel cells. In this study, the in situ degradation behaviour of a commercial GDL carbon fiber paper with MPL was investigated under a combination of elevated temperature and elevated flow rate conditions. To avoid the possible impact of the catalyst layer during degradation test, different barriers without catalyst were utilized individually to isolate the anode and cathode GDLs. Three different barriers were evaluated on their ability to isolate GDL degradation and their similarity to a fuel cell environment, and finally a novel Nafion/MPL/polyimide barrier was chosen. Characterization of the degraded GDL samples was conducted through the use of various diagnostic methods, including through-plane electrical resistivity measurements, mercury porosimetry, relative humidity sensitivity, and single-cell performance curves. Noticeable decreases in electrical resistivity and the hydrophobic properties were detected for the degraded GDL samples. The experimental results suggested that material loss plays an important role in GDL degradation mechanisms, while excessive mechanical stress prior to degradation weakens the GDL structure and changes its physical property, which consequently accelerates the material loss of the GDL during aging. Crown

“…Cho et al [37] reported that mechanical strength and cost of the carbon composite plates are necessary to be improved. Thus, stainless steels have attracted wide attention to substitute the Page 4 of 34 A c c e p t e d M a n u s c r i p t 4 carbonaceous bipolar plates [38][39][40][41][42][43][44]. However, stainless steels could be readily corroded in the PEMFC environment because the SO 4 2− and F − anions released from the membrane polymer in the course of cell operation, leading to low pH.…”

Section: Page 3 Of 34mentioning

confidence: 99%

“…Yuan et al [1] reported EIS has already become a primary tool in PEMFC research. EIS method is also used effectively for analyses of the amount of catalysts [2][3][4][5], nafion content [3,[6][7][8], membrane thickness [9,10], GDL structure [11][12][13][14][15][16][17][18][19], proton conductivity [20][21][22][23][24][25][26], humidification condition [3,9,[27][28][29][30] and stack [24,[31][32][33][34][35][36]. For example, Paganin et al [2] and Song et al [3] suggested that charge transfer resistance is much smaller with increasing amount of catalysts.…”

Section: Page 3 Of 34mentioning

confidence: 99%

Evaluation of polymer electrolyte membrane fuel cells by electrochemical impedance spectroscopy under different operation conditions and corrosion

Kumagai¹,

Ichikawa

Yashiro

2010

Electrochemical impedance spectroscopy (EIS) was employed for in situ diagnosis for polymer electrolyte membrane fuel cells during operation. First, EIS was measured as a function of operation parameters such as applied current density, gas flow rates and gas humidification temperature. The resistance that correlated with conductivity of the membrane and the contact resistance between bipolar plate and gas A c c e p t e d M a n u s c r i p t 2 diffusion layer (GDL) was set as R m in the assumed equivalent circuit. The charge transfer resistances were considered for cathode (R ct (C)). The value of R ct (C) was sensitive to the parameters that affected cell voltage. Additionally, the diffusion resistance (R d ) was ascribed to the effect of oxygen supply and drainage of generated water. Second, the influence of corrosion of type 430 stainless steel bipolar plates was evaluated by EIS method during operation. Corrosion of the stainless steel bipolar plates resulted in an increase in the value of R d .