Quantitative analysis of carbon corrosion during fuel cell start-up and shut-down by anode purging

Linse, Nicolas; Scherer, Günther G.; Wokaun, Alexander; Gubler, Lorenz

doi:10.1016/j.jpowsour.2012.07.037

Cited by 64 publications

(39 citation statements)

References 41 publications

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“…This may be because degradation depends on the residence time of the gas front which passes through the cell and thus on the specific test protocol for start up and shut down. 65 A detailed discussion of degradation phenomena in start/ stop procedures can be found here. 13 …”

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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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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“…However, in terms of durability, this material exhibits important disadvantages related to its poor electrochemical and chemical resistance in the aggressive operational conditions of the HT‐PEMFC. These harsh conditions are given due to the polibenzimidazole (PBI) based membranes (typical membranes used in HT‐PEMFC) must be doped with phosphoric acid in order to get acceptable protonic condition, and this acid, combined with the high temperature operational range, performs a strong degradation on the Vulcan carbon based electrode components . Furthermore, the electrochemical carbon corrosion starts to appear at potentials over 0.267 V vs RHE, resulting in a several corrosion at voltages over 1.2 V. These voltage values are easily achieved during the turn‐on and shut‐down processes during the fuel cell operation, and also in open circuit voltage (OCV) conditions ,.…”

Section: Introductionmentioning

confidence: 99%

“…These harsh conditions are given due to the polibenzimidazole (PBI) based membranes (typical membranes used in HT‐PEMFC) must be doped with phosphoric acid in order to get acceptable protonic condition, and this acid, combined with the high temperature operational range, performs a strong degradation on the Vulcan carbon based electrode components . Furthermore, the electrochemical carbon corrosion starts to appear at potentials over 0.267 V vs RHE, resulting in a several corrosion at voltages over 1.2 V. These voltage values are easily achieved during the turn‐on and shut‐down processes during the fuel cell operation, and also in open circuit voltage (OCV) conditions ,. The degradation of the Vulcan carbon carries out some problems related with the performance and durability of the fuel cell (mass transfer limitation, migration and agglomeration of the platinum particles, or the increasing of the ohmic resistance of the electrodes, due to the degradation of the carbonaceous structure of the electrode).…”

Section: Introductionmentioning

confidence: 99%

High‐Stability Electrodes for High‐Temperature Proton Exchange Membrane Fuel Cells by Using Advanced Nanocarbonaceous Materials

et al. 2017

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This work studies the stability and performance of a cathodic electrode for high‐temperature proton exchange membrane (HT‐PEMFC) systems prepared with a carbon nanosphere (CNS) based microporous layer and carbon nanofibers (CNFp) used as a catalyst support. The obtained results are compared with a standard Vulcan carbon XC72 based electrode. With this purpose, two membrane−electrode assemblies (MEAs) were prepared using the cathodic electrodes and tested in a 25 cm2 HT‐PEMFC system. Preliminary short‐life tests around 330 h were carried out with both MEAs. During the tests, different characterization procedures, consisting of polarization curves, spectroscopy impedance analysis, cyclic voltammetry and linear sweep voltammetry were performed in order to evaluate the evolution of the main stability and performance parameters of the MEAs. Results showed that the application of these new materials increases positively the stability of the MEA in comparison with the standard Vulcan carbon XC72 material, with a negligible decrease in the performance of the advanced MEA during all tests, making these results very promising to overcome the service lifetime limitations of these systems.

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“…However during the start-up and shut-down operation, the cathode can reach potentials higher than 1V (5,6). Therefore, carbon BPPs are prone to corrosion in fuel cells for automotive applications.…”

Section: Introductionmentioning

confidence: 99%

Improved Water Management with Thermally Sprayed Coatings on Stainless Steel Bipolar Plates of PEMFC

et al. 2015

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We develop a thermally sprayed Ti coating for PEMFC stainless steel (ss) bipolar plates. It is subsequently modified with Au by electro-deposition. SEM reveals that the Au/Ti coating is 30.8 µm thick and rough. The presence of TiO 2 between Ti and Au is negligible, as confirmed by XRD and XPS. Potendiodynamic characteristics in O 2 -saturated 0.5 M H 2 SO 4 show that the Au/Ti/ss samples have comparable corrosion currents to Au/ss but higher corrosion potentials. The interfacial contact resistance (ICR) of Au/Ti/ss is 8.6 mΩ cm 2 under a compaction pressure of 140 N cm -2 . The performances of PEMFCs with Au and Au/Ti are similar at cell voltages higher than 0.75 V. However, at 0.6 V the Au/Ti coating diminishes the current and pressure instabilities of the PEMFC operating under strong flooding conditions. The effect also occurs in the oscillation frequency, confirming the unique property of Au/Ti for reducing the effect of flooding.

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Quantitative analysis of carbon corrosion during fuel cell start-up and shut-down by anode purging

Cited by 64 publications

References 41 publications

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

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

High‐Stability Electrodes for High‐Temperature Proton Exchange Membrane Fuel Cells by Using Advanced Nanocarbonaceous Materials

Improved Water Management with Thermally Sprayed Coatings on Stainless Steel Bipolar Plates of PEMFC

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