In situ EPR investigation of polymer electrolyte membrane degradation in fuel cell applications

Panchenko, Alexander; Dilger, Herbert; Möller, Einar; Sixt, Torsten; Roduner, Emil

doi:10.1016/j.jpowsour.2003.09.047

Cited by 143 publications

(91 citation statements)

References 18 publications

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“…It was therefore difficult to extract a strong causal relationship between fuel cell operating parameters, ROS generation rates, and ROS-induced chemical degradation. The presence of ROS in PEM fuel cells has been directly identified by electron paramagnetic resonance (EPR) measurements (21)(22)(23)(24). However, these measurements are limited to cells that fit within the EPR probe and cannot be translated to subscale or larger scale cells operating under realistic conditions.…”

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confidence: 99%

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

Prabhakaran

Arges

Ramani

2012

Proc. Natl. Acad. Sci. U.S.A.

145

126

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A fluorescent molecular probe, 6-carboxy fluorescein, was used in conjunction with in situ fluorescence spectroscopy to facilitate realtime monitoring of degradation inducing reactive oxygen species within the polymer electrolyte membrane (PEM) of an operating PEM fuel cell. The key requirements of suitable molecular probes for in situ monitoring of ROS are presented. The utility of using free radical scavengers such as CeO 2 nanoparticles to mitigate reactive oxygen species induced PEM degradation was demonstrated. The addition of CeO 2 to uncatalyzed membranes resulted in close to 100% capture of ROS generated in situ within the PEM for a period of about 7 h and the incorporation of CeO 2 into the catalyzed membrane provided an eightfold reduction in ROS generation rate.fuel cells | Nafion® degradation | hydroxyl radicals | hydroperoxyl radicals | miniature fluorescence probe H ydrogen/air (H 2 ∕air) polymer electrolyte membrane (PEM) fuel cells possess high efficiency and modularity. However, significant technical advances are required to facilitate fuel cells' commercialization and widespread use in targeted applications in the automotive, portable power, and military sectors. A key technological issue that remains to be addressed is component durability under an array of adverse operating conditions. The ionexchange membrane in a PEM fuel cell is one of the components whose limited long-term durability is of concern. The PEM undergoes mechanical, thermal, and chemical degradation during fuel cell operation (1-8). The chemical degradation process that takes place in a H 2 ∕O 2 PEM fuel cell is attributed to reactive oxygen species (ROS) that are generated in situ through both chemical and electrochemical pathways during fuel cell operation. Hydrogen peroxide (H 2 O 2 ) is an ROS and is often an intermediate formed in both pathways and is known to form free radical ROS in the presence of transition metal ions via the Fenton mechanism (9-12). These free radical ROS, namely hydroxyl and hydroperoxyl radicals, are amongst the strongest oxidizing agents known. ROS initiate oxidative degradation of both the PEM backbone and the side chains that contain ionic groups that are essential for ion conduction (13-16). The adverse consequences of these degradation modes (e.g., membrane thinning, pin-hole formation, and loss of ionic conductivity) eventually contribute to catastrophic cell and stack failure. Complete elimination of ROS generation and PEM chemical degradation, while a worthy goal, is difficult due to constraints in terms of membrane materials, choice of fuel and oxidant, and fuel cell operating conditions. Therefore, it is imperative to develop effective mitigation strategies that minimize the rate and extent of PEM degradation.Prior to proposing an effective mitigation strategy, it is essential to quantify the rate of ROS generation within the PEM during fuel cell operation. However, detecting the presence of ROS within the PEM of an operating fuel cell is an extremely difficult proposition because free ra...

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mentioning

confidence: 99%

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

Prabhakaran

Arges

Ramani

2012

Proc. Natl. Acad. Sci. U.S.A.

145

126

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“…These methods include electron paramagnetic resonance (EPR) investigations of PEM degradation, [29,30] the construction of PEMFCs using transparent materials, [31][32][33][34][35][36][37][38][39] the use of neutron imaging, [40][41][42][43][44][45] and 1 H NMR microscopy. [46][47][48][49][50] For example, numerous studies have used transparent PEMFCs to investigate the formation of CO 2 (g) in the anode flow field of direct methanol fuel cells [31,32] and the behavior of water in gas diffusion layers.…”

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confidence: 99%

The Use of¹H NMR Microscopy to Study Proton‐Exchange Membrane Fuel Cells

2006

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To understand proton-exchange membrane fuel cells (PEMFCs) better, researchers have used several techniques to visualize their internal operation. This Concept outlines the advantages of using 1H NMR microscopy, that is, magnetic resonance imaging, to monitor the distribution of water in a working PEMFC. We describe what a PEMFC is, how it operates, and why monitoring water distribution in a fuel cell is important. We will focus on our experience in constructing PEMFCs, and demonstrate how 1H NMR microscopy is used to observe the water distribution throughout an operating hydrogen PEMFC. Research in this area is briefly reviewed, followed by some comments regarding challenges and anticipated future developments.

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“…resolved in 1D through the PEM thickness from the solution of [17] where the source/sink term is related to the Fenton reactions describing the H 2 O 2 decomposition in OH • /OOH • in presence of the Fenton's cations. In this paper, for demonstration purposes, only the presence of Fe 2+ and the Fenton reactions reported in Table III were considered.…”

Section: Overall Methodologymentioning

confidence: 99%

“…[16][17][18][19] The most plausible origins of these ions are the degradation of iron containing end-plates which are used in the PEMFCs, and the oxidation of the pipes in the reactants management system. 20,21 Additionally, some debate still remains about the role of the precipitated Pt (arising from electrochemical dissolution mainly in the cathode CL) on catalyzing the H 2 O 2 decomposition.…”

Section: F60mentioning

confidence: 99%

A Multiparadigm Modeling Investigation of Membrane Chemical Degradation in PEM Fuel Cells

Quiroga

Malek

Franco

2015

J. Electrochem. Soc.

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We report a multi-paradigm model of the membrane chemical degradation in Polymer Electrolyte Membrane Fuel Cells (PEMFCs), by combining Coarse-Grained Molecular Dynamics (CGMD) and a multiscale cell performance model. CGMD is used to generate structural databases that relate the amount of detached (degraded) ionomer sidechains with the water content and the resulting PEM meso-microporous structure. The multiscale cell performance model describes the electrochemical reactions and transport mechanisms occuring in the electrodes from an on-the-fly coupling between Kinetic Monte Carlo (KMC) sub-models parametrized with Density Functional Theory (DFT) data and (partial differential equations-based) continuum sub-models. Furthermore, the performance model includes a kinetic PEM degradation sub-model which integrates the CGMD database. The cell model also predicts the instantaneous PEM sidechain content and conductivity evolution at each time step. The coupling of these diverse modeling paradigms allows one to describe the feedback between the instantaneous cell performance and the intrinsic membrane degradation processes. This provides detailed insights on the membrane degradation (sidechain detachment as well as water reorganization within the PEM) during cell operation. This novel modeling approach opens interesting perspectives in engineering practice to predict materials degradation and durability as a function of the initial chemical composition and structural properties in electrochemical energy conversion and storage devices. From the second half of the twentieth century, Polymer Electrolyte Membrane Fuel Cells (PEMFCs) have attracted much attention due to their potential as a clean power source for vehicles traction. Market introduction of FC vehicles is being recognized of highest priority in many developed countries due to their impact on the reduction of energy consumption and greenhouse gas emissions. However, PEMFC technologies have not yet reached all the requirements to be competitive, in particular regarding their high production cost of Membrane Electrode Assemblies and their low durability.Indeed, meso/micro-structural degradation leading to the PEMFC components aging is attributed to several complex physicochemical mechanisms not yet completely understood. The associated components meso/micro-structural changes translate into irreversible longterm cell power degradation.1-3 For instance, dissolution and redistribution of the catalyst reduces the specific catalyst surface area and the electrochemical activity. The corrosion of the catalyst carbon-support and loss or decrease of the hydrophobicity caused by an alteration of the Polytetrafluoroethylene in Catalyst Layers (CLs), Microporous Layers and Gas Diffusion Layers also affect the water management in the cell and thus the electrochemical performance.Regarding the polymer electrolyte in PEMFCs, a large number of materials has been tested, including sulfonated hydrocarbon polymers, phosphoric acid doped polybenzimidazole, polymer-inorganic composit...

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In situ EPR investigation of polymer electrolyte membrane degradation in fuel cell applications

Cited by 143 publications

References 18 publications

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

The Use of¹H NMR Microscopy to Study Proton‐Exchange Membrane Fuel Cells

A Multiparadigm Modeling Investigation of Membrane Chemical Degradation in PEM Fuel Cells

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In situ EPR investigation of polymer electrolyte membrane degradation in fuel cell applications

Cited by 143 publications

References 18 publications

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

Investigation of polymer electrolyte membrane chemical degradation and degradation mitigation using in situ fluorescence spectroscopy

The Use of1H NMR Microscopy to Study Proton‐Exchange Membrane Fuel Cells

A Multiparadigm Modeling Investigation of Membrane Chemical Degradation in PEM Fuel Cells

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The Use of¹H NMR Microscopy to Study Proton‐Exchange Membrane Fuel Cells