Effect of operating conditions on carbon corrosion in polymer electrolyte membrane fuel cells

Lim, Kang-Won; Oh, Hyung Suk; Jang, Sang Eun; Ko, Young‐Jin; Kim, Hyun Jong; Kim, Han Sung

doi:10.1016/j.jpowsour.2009.04.006

Cited by 108 publications

(65 citation statements)

References 20 publications

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“…The voltage loss by proton conduction resistance through the membrane is given by (taken from Ref. [16] Whereby the t mem refers to the membrane thickness (15 or 18 μm) and the apparent activation energy for proton conduction (E act H + ) was taken as 6 kJ/mol. 22 The electrical bulk and contact resistances (η [18] Under the simplifying assumption that the OER in the electrolytic part of the cell can be neglected, an analytical expression for the polarization curve of the electrolytic cell could be obtained.…”

Section: Kinetic H 2 /Air Anode Susd Modelmentioning

confidence: 99%

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PEM Fuel Cell Start-up/Shut-down Losses vs Temperature for Non-Graphitized and Graphitized Cathode Carbon Supports

Mittermeier

Weiß

Hasché

et al. 2016

J. Electrochem. Soc.

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One of the key figures for the success of proton exchange membrane fuel cells (PEMFCs) in automotive applications is lifetime. Damage of the cathode carbon support, induced by hydrogen/air fronts moving through the anode during start-up/shut-down (SUSD), is one of the lifetime limiting factors. In this study, we examine the impact of varying the temperature at which SUSD events take place, both experimentally and by a kinetic model. For MEAs with conventional carbon supports, the model prediction of carbon oxidation reaction (COR) currents as a function of temperature matches well with the temperature dependence of experimentally determined SUSD degradation rates (predicting ≈8-fold lower COR currents compared to ≈10-fold lower measured degradation rates at 5 • C compared to 80 • C). This, however, is not the case for MEAs with graphitized carbon supports, where a factor of ≈39 lower COR currents are predicted when decreasing SUSD temperature from 80 to 5 • C, in contrast to the measured decrease by a factor of ≈10. As we will show, this is explained by a change of the governing degradation mechanism from predominantly carbon corrosion induced losses at higher temperature to predominantly voltage cycling induced platinum surface area losses near/below room temperature. several practical aspects of automotive PEMFC operation remain challenging to date.5 One such phenomenon is the degradation caused by start-up and/or shut-down (SUSD) of the PEMFC, where a H 2 /air anode gas front moves through the anode flow-field, which was first discussed in the scientific literature by Reiser et al. 6 in 2005 (note that it was described in the patent literature as early as 2002 7 ). Typically, during an uncontrolled shut-down, air will leak slowly into the H 2 compartment through leaks in the back-pressure valve, through the stack sealing or by crossover through the membrane, which was found to lead to substantial damage of the cathode catalyst carbon support in the MEA (membrane electrode assembly). 6 One of the early methods to mitigate this damage was the use of a controlled shut-down, in which a high-flow air purge of the anode compartment was applied in order to minimize the H 2 /air anode front residence time, which is proportional to the induced damage. 8The reactions occurring during the passing of the H 2 /air anode front through the anode flow-field are listed in Figure 1a (slightly modified from what was shown in Ref. 9 and 10), illustrating the partially H 2 -filled (lower left segment, colored in red) and partially air-filled (upper left segment, colored in blue) anode, opposite of the air-filled cathode flow-field (right blue segments) and separated by the proton conducting membrane (orange). While electrons can be well conducted in-plane, mainly via the diffusion media (DM) and flow fields (FF), the in-plane proton conduction resistance through the membrane is very high, so that significant proton conduction in-plane can be supported only over very short distances across the H 2 /air anode front, namely over a ...

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Section: Kinetic H 2 /Air Anode Susd Modelmentioning

confidence: 99%

“…16 Only in the studies by Kreitmeier et al 17 and by Jo et al 18 the temperature was varied while Figure 1. Schematic of a start-up and/or shut-down (SUSD) event in a PEMFC, sketching the passage of a H 2 /air anode front through the anode flow-field (H 2 -filled regions in red, air-filled regions in blue) while the cathode flow-field is filled with air.…”

mentioning

confidence: 99%

PEM Fuel Cell Start-up/Shut-down Losses vs Temperature for Non-Graphitized and Graphitized Cathode Carbon Supports

Mittermeier

Weiß

Hasché

et al. 2016

J. Electrochem. Soc.

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“…Fuel starvation induced uneven currency diffusion, which had an increasing trend in the anode inlet and a decreasing trend in the outlet [4]; hydrogen oxidation reaction and water oxidation occurred at different regions of the electrode simultaneously. Due to the lack of hydrogen supply, which cannot satisfy the fuel cell system's electron requirements, the fuel cell system would spontaneously increase the anode potential as a result of an abnormal reaction or cell performance degradation, such as water oxidation, carbon corrosion, and so on, to obtain extra electrons [28]. In a galvanostatic operation or fuel cell stack, it will decompose the electrode material or the sick cell, like an electrolytic cell.…”

Section: Pemfc Anodementioning

confidence: 99%

“…As an indispensable component of the fuel cell system, carbon supports tend to corrode with water to produce CO 2 at high potential [28]. Thanks to a large number of micropores, catalyst particles can be physically segregated by carbon supports to prevent particle sintering and catalyst dissolution, which can improve catalyst particles' specific surface area [35,36].…”

Section: Consequences Of Cell Reversalmentioning

confidence: 99%

Proton Exchange Membrane Fuel Cell Reversal: A Review

et al. 2016

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Abstract:The H 2 /air-fed proton exchange membrane fuel cell (PEMFC) has two major problems: cost and durability, which obstruct its pathway to commercialization. Cell reversal, which would create irreversible damage to the fuel cell and shorten its lifespan, is caused by reactant starvation, load change, low catalyst performance, and so on. This paper will summarize the causes, consequences, and mitigation strategies of cell reversal of PEMFC in detail. A description of potential change in the anode and cathode and the differences between local starvation and overall starvation are reviewed, which gives a framework for comprehending the origins of cell reversal. According to the root factor of cell starvation, i.e., fuel cells do not satisfy the requirements of electrons and protons of normal anode and cathode chemical reactions, we will introduce specific methods to mitigate or prevent fuel cell damage caused by cell reversal in the view of system management strategies and component material modifications. Based on a comprehensive understanding of cell reversal, it is beneficial to operate a fuel cell stack and extend its lifetime.

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“…20,40,44 At a constant potential of 1.4 V no difference could be detected in carbon corrosion as humidified oxygen or humidified nitrogen was applied. 45 Additionally, the effect of cycling enhances corrosion in general. 8,23,44,46 The carbon corrosion in PAFC is described in a similar way by oxidation of surface groups.…”

Section: F154mentioning

confidence: 99%

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

Reimer

Schumacher

Lehnert

2014

J. Electrochem. Soc.

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Accelerated stress tests are commonly applied in order to obtain a prediction of fuel cell life time within a short testing period. The stress test in this work considers a fuel cell which is constantly under load with frequent periods of very high current. Four different cells were operated each with a specific load profile. As a result severe performance degradation was observed in the region of high current densities. A short overview over the phenomena which may contribute to this specific fuel cell degradation is compiled from literature. Based on this overview major degradation modes are identified and combined with a simple polarization curve model. The modeling results allow for two different interpretations. Carbon corrosion reactions can explain the observed effects if cell voltage is assumed as the driving force for degradation. A better fit was obtained by using the overall heat flux as degradation criterion. In this case an increase in local temperature could lead to redistribution and loss of phosphoric acid from the MEA. The expected lifetime of a polymer electrolyte fuel cell (PEFC) ranges from 5 000 h for mobile application to 40 000 h for stationary application.1,2 In order to gain information about time dependent degradation in advance accelerated test protocols are used.3,4 Depending on the design of these tests valuable information about the nature of the main degradation mode under the applied operation conditions can be obtained. Despite the difference in operation conditions for PEFC, HT-PEFC and PAFC the structure and material of the electrodes are almost the same. Consequently, observed degradation phenomena show strong similarities.5 A good description of these phenomena can be found in several review papers 6-13 as well as in at least four books 1,2,14,15 where recent experimental facts and interpretations are summarized. A compact description can also be found in a recent review paper on modeling transport phenomena in PEFCs. 16 The purpose of this paper is to present the results of a specific accelerated degradation test for high temperature polymer electrolyte fuel cells (HT-PEFC) with phosphoric acid doped polybenzimidazole (PBI/H 3 PO 4 ) membranes. The fuel cell is constantly under load with frequent periods of very high current. In order to accelerate degradation effects the fuel cell is operated beyond it's point of maximum power. A simple polarization curve model is used as starting point for the analysis of data. Based on this first analysis a degradation model is proposed which allows for a straightforward physical interpretation. The complexity of degradation effects which occur simultaneousy usually leads to models which either resolve a specific mechanism in depth or describe more general effects. This paper aims at general effects which requires a broader understanding of degradation. In the following it is attempted to provide an overview over the phenomena which may contribute to fuel cell degradation. Based on this overview major degradation modes are identified and ...

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Effect of operating conditions on carbon corrosion in polymer electrolyte membrane fuel cells

Cited by 108 publications

References 20 publications

PEM Fuel Cell Start-up/Shut-down Losses vs Temperature for Non-Graphitized and Graphitized Cathode Carbon Supports

PEM Fuel Cell Start-up/Shut-down Losses vs Temperature for Non-Graphitized and Graphitized Cathode Carbon Supports

Proton Exchange Membrane Fuel Cell Reversal: A Review

Accelerated Degradation of High-Temperature Polymer Electrolyte Fuel Cells: Discussion and Empirical Modeling

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