A Carbon Corrosion Model to Evaluate the Effect of Steady State and Transient Operation of a Polymer Electrolyte Membrane Fuel Cell

Pandy, Arun; Yang, Zhiwei; Gummalla, Mallika; Atrazhev, V.M.; Kuzminyh, Nikolay Yu.; Sultanov, Vadim I.; Burlatsky, S. F.

doi:10.1149/2.036309jes

Cited by 66 publications

(71 citation statements)

References 17 publications

(54 reference statements)

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“…Upon holding the electrode potential at 1.1 V or 1.4 V, the oxidation currents start to decrease down to a stable value. These currents may be indicative of some electro-oxidation or electro-gasification (CO 2 evolution) processes under steady state conditions [21][22][23][24][25][26][27]. In addition, oxygen evolution reaction may also contribute to this current.…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

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Enhanced electro-oxidation resistance of carbon electrodes induced by phosphorus surface groups

Berenguer

Ruiz-Rosas

Gallardo

et al. 2015

Carbon

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ABSTRACT:The electro-oxidation of carbon materials enormously degrades their performance and limits their wider utilization in multiple electrochemical applications.In this work, the positive influence of phosphorus functionalities on the overall electrochemical stability of carbon materials has been demonstrated under different conditions. We show that the extent and selectivity of electroxidation in P-containing carbons are completely different to those observed in conventional carbons without P.The electro-oxidation of P-containing carbons involves the active participation of phosphorus surface groups, which are gradually transformed at high potentials from less-to more-oxidized species to slow down the introduction of oxygen groups on the carbon surface (oxidation) and the subsequent generation of (C*OOH)-like unstable promoters of electro-gasification. The highest-oxidized P groups (-C-O-P-like species) seem to distribute the gained oxygen to neighboring carbon sites, which finally suffer oxidation and/or gasification. So it is thought that P-groups could act as mediators of carbon oxidation although including various steps and intermediates compared to electroxidation in P-free materials.

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Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

“…However, little is unambiguously known regarding the mechanism of electrochemical oxidation [21][22][23][24][25]. As a consequence, few strategies to improve the carbon electro-oxidation resistance have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Enhanced electro-oxidation resistance of carbon electrodes induced by phosphorus surface groups

Berenguer

Ruiz-Rosas

Gallardo

et al. 2015

Carbon

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“…100 In order to additionally include effects like surface oxide groups and OH radicals a model with 16 separate reaction rates was proposed. 101 The model shows that the formation of surface oxides on platinum and carbon support is a key feature in the degradation reaction. In order to resolve local carbon corrosion anode 102 and cathode 103 two dimensional models have been developed which link corrosion to distribution of local current density.…”

Section: Degradation Modelsmentioning

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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“…According to Pandy et al 43 complete carbon corrosion of the surface COH via this pathway requires high potential (0.95V vs. RHE) to completely oxidize to carbon dioxide.…”

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confidence: 99%

“…43,44 It is through this pathway that we hypothesize that carbon corrosion occurs when foreign cations are present in the cathode.…”

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confidence: 99%

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

Banas

Uddin

Park

et al. 2018

J. Electrochem. Soc.

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Four hundred hour fuel cell tests were performed on commercial, as-received and Ca 2+ contaminated catalyst coated membranes (CCMs) to evaluate the effects of long term exposure of foreign cations on fuel cell performance and degradation. Following testing, significant thinning of the cathode catalyst layer was observed across the entire active area in the contaminated cell, while only localized thinning was observed in the as-received baseline CCM. Analysis of the elemental maps and line intensity profiles of platinum (Pt) obtained from energy dispersive X-ray spectrum (EDX) shows minimal change in total platinum content across the thickness of the catalyst layer, and hence loss of carbon is suspected to be the cause of the thinning. A numerical model is employed to show the foreign cation redistribution during testing, which shows proton depletion in the cathode catalyst layer when the CCM is contaminated with foreign cations. We hypothesize that this lack of protons leads to accelerated carbon corrosion in the cathode to supply protons to oxygen reduction where foreign cations block transport of protons. A carbon corrosion scheme is presented which shows that under the operating potentials of the cell, carbon oxidation can occur, leading to the observed thinning. The polymer electrolyte fuel cell (PEFC), a promising clean energy source for automobile application, still needs to overcome durability issues originating from various sources.1 Cationic impurities originated from either ambient air (e.g. roadside contaminants) or from the corrosion of stack and balance of plant components can significantly decrease the performance and life time of PEFCs. [1][2][3][4] In this paper, we report on the influence of foreign cationic contamination on the thinning of the cathode catalyst layer during non-accelerated testing. Long duration (400hr) testing was conducted using commercial catalyst coated membranes which showed significant catalyst layer thinning in a calcium cation contaminated cell, this thinning of the cathode catalyst layer was not observed in a non-contaminated baseline. While foreign cations are known to cause several degradation mechanisms in PEFCs, no study has examined the influence of cationic contamination on carbon corrosion, which we believe causes the thinning of the catalyst layer.To understand the impact and mechanism of cation contamination in PEFC, several modeling 5-11 and experimental studies 12-33 have been conducted, including ex-situ contamination of the polymer membrane with various cations before the test as well as injecting cations into the air or fuel stream during the cell test. Okada and co-workers extensively investigated the effect of various metal cations (Li + , Na + , Ca 2+ , Fe 2+ , Ni 2+ , Cu 2+ , Rb 2+ , Cs + ) on the transport properties of perfluorosulfonic acid (PFSA) membranes, thermodynamics and oxygen reduction reaction (ORR) kinetics. 5,[13][14][15][16][17][18] They reported that, with the exception of Li + , all foreign cations have higher affinity toward the sulfo...

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A Carbon Corrosion Model to Evaluate the Effect of Steady State and Transient Operation of a Polymer Electrolyte Membrane Fuel Cell

Cited by 66 publications

References 17 publications

Enhanced electro-oxidation resistance of carbon electrodes induced by phosphorus surface groups

Enhanced electro-oxidation resistance of carbon electrodes induced by phosphorus surface groups

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

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

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