Impact of Accelerated Stress Tests on High Temperature PEMFC Degradation

Schonvogel, Dana; Rastedt, Maren; Wagner, Peter; Wark, Michael; Dyck, Alexander

doi:10.1002/fuce.201500160

Cited by 53 publications

(39 citation statements)

References 24 publications

(49 reference statements)

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“…ECSA loss in first week after the AST period is reported in literature. The ECSA loss could be attributed to the removal of loosely bound catalyst nanoparticles from the electrochemical active centers during initial operation of MEA . Thereafter ECSA starts to decrease with a steep drop with increasing number of potential cycles.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Potential Cycling on High Temperature PEM Fuel Cell with Different Flow Field Designs

et al. 2019

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Degradation of phosphoric acid doped polybenzimidazole membrane based fuel cells under accelerated potential cycling conditions is investigated in current study. Three unit cells with identical high temperature membrane electrode assembly were assembled with three different cathode flow field designs. The fuel cell is cycled between 0.5 V and 0.9 V with 3 min dwelling time for each voltage set point. Performance degradation mechanisms associated with differences in cathode flow design are identified. The fuel cell with multiple serpentine design is operated for a maximum of 4,821 potential cycles with only 38.6% of initial performance remaining at the end‐of‐test (EoT), whereas straight and parallel design operated for only 3,188 cycles. The electrochemical characterization studies reveal the cause of observed performance losses from polarization curves. Irrespective of the design type used there are very high activation losses observed which accelerated with accelerated stress tests (AST) testing. The impedance studies reveal high charge transfer resistance related to increased platinum crystal growth on cathode and reduced electrochemical surface area (ECSA) of catalyst. Overall the AST results in irreversible performance loss and severe degradation of the cathode catalyst support and catalyst itself.

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Section: Resultsmentioning

confidence: 99%

The Effect of Potential Cycling on High Temperature PEM Fuel Cell with Different Flow Field Designs

et al. 2019

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“…In addition to migration, electrolyte transfer from the MEA might arise on account of decreased viscosity and hygral expansion of the electrolyte as the acid absorbs water, which is produced at high rates when the current density is high. 28,39 The volatility of phosphoric acid will also vary with water content. 16,17 Intuitively, adding water to concentrated phosphoric acid should dilute the acid and cause a lowering of its vapor pressure in accordance with Raoult's law.…”

Section: Resultsmentioning

confidence: 99%

“…However, a significant caveat should be emphasized in that the acid-loss rate has been suggested to increase over the course of long-term operation, an observation that has been claimed based on loss estimations via off-gas analysis. 28 On the other hand, this might be an artifact of acid re-condensation before reaching the location where the remainder is actually collected for analysis. 8 If so, an increasing rate of acid loss might be explained by the impact of re-condensation dwindling during operation because the path downstream of the MEA approaches saturation with acid.…”

Section: F3060mentioning

confidence: 99%

Long-Term Durability of PBI-Based HT-PEM Fuel Cells: Effect of Operating Parameters

Søndergaard

Cleemann

Becker

et al. 2018

J. Electrochem. Soc.

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This work studies the long-term durability of high-temperature polymer electrolyte membrane fuel cells based on acid-doped polybenzimidazole membranes. The primary focus is on acid loss via the evaporation mechanism, which is a major cause of degradation in applications that involve long-term operation. Durability is assessed for 16 identically fabricated membrane electrode assemblies (MEAs), and evaluations are carried out using operating parameters as stressors with gas stoichiometries ranging from 2 to 25, current densities from 200 to 800 mA cm −2 , and temperatures of 160 or 180 • C. Cell diagnostics are composed of time resolved polarization curves, post mortem analysis, and in situ temperature measurements. A major part of the cell degradation during these steady-state tests can be ascribed to increasing area-specific series resistance. By means of post mortem acid-loss measurements, the degradation is correlated to the temperature and to the accumulated gas-flow volume. Such relations are indicative of acid loss via evaporation. Current density also plays a critical role for the acid loss and, thus, for the overall cell degradation. The effect of current is likely tied to mechanisms that involve water generation, migration of electrolyte ions, and locally elevated temperature inside the Since the polybenzimidazole (PBI) polymer acts as a Brønsted base in relation to phosphoric acid, membranes of PBI can be doped with phosphoric acid through acid-base complexation. Some of the H 3 PO 4 molecules, 2 per polymer repeat unit, are then bound to the basic functional sites of the polymer. However, excess acid is essential in order to attain a conductivity that is high enough for use as electrolyte in a polymer electrolyte membrane fuel cell (PEMFC). Fuel cells based on this type of electrolyte are known as high-temperature (HT-)PEMFCs, typically operating at temperatures of 140-180• C. Phosphoric acid-doped PBI membranes can be prepared either by direct (or so-called sol-gel) casting from a solution of PBI dissolved in polyphosphoric acid (PPA) or by solution casting of a PBI film via solvent evaporation, for which acid-doping follows subsequently. 1 For HT-PEMFCs, the cell performance usually increases to a stable state within the first few hundred hours of operation. This activation of the cell might be a consequence of acid redistribution in the membrane electrode assembly (MEA).2-4 Such redistribution of acid also implies susceptibility to its loss, however, because it is a testament to the mobility of the doping-acid. [5][6][7] As reviewed by Jakobsen et al., a number of mechanisms have been proposed to explain the loss of doping-acid from PBI membranes, including evaporation into the gas phase and a so-called steam distillation mechanism, the latter of which has been proposed governed by temperature as well as humidity. 9 Migration of electrolyte ions might also be an issue with respect to acid loss, particularly if the proton transference number deviates significantly from the maximum value for phosphori...

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“…[92][93] An in-situ accelerated stress test (AST) was then carried out to assess the durability of the MEA. Standardized AST protocols are well developed for PEM fuel cell technology [94][95][96] while the establishment of standardized AST protocols for PEM water electrolysis is still under development. 97 We exploit here an AST protocol for a quick (over 24 h) evaluation of the MEA durability, adapted from the work performed in the NOVEL EU Project.…”

Section: Pem Electrolyzer Testingmentioning

confidence: 99%

Nonprecious Bimetallic Iron–Molybdenum Sulfide Electrocatalysts for the Hydrogen Evolution Reaction in Proton Exchange Membrane Electrolyzers

et al. 2020

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In this study, we report the synthesis and characterization of non-precious bimetallic ironmolybdenum sulfide bioinspired electrocatalysts for the hydrogen evolution reaction (HER).Iron-molybdenum sulfide materials were obtained through three distinct scalable synthetic approaches using microwave irradiation or heat treatment in furnace under inert and reductive atmospheres. These electrocatalysts were combined with carbon nanotubes (CNTs) and their activity for the hydrogen evolution reaction (HER) was studied in acidic environment. The most efficient composite material of the series was obtained by microwave synthesis and displays a current density per geometric area of 10 mAcm -2 at an overpotential of 140 mV with unity faradaic efficiency for hydrogen evolution. This composite cathode catalyst was implemented into a proton exchange membrane (PEM) electrolyzer single cell with iridium black as anode catalyst and could be operated at 0.5 Acm -2 requiring less than 300 mV additional voltage compared to Pt, and with remarkable stability during accelerated stress testing.PEM-compatible oxygen evolution reaction (OER) catalysts based on Earth-abundant elements. [99][100] ASSOCIATED CONTENT Supporting Information. Supporting Information. Additional experimental details, PEM electrolyzer setup, SEM images, Raman spectra, XPS spectra, electrochemical results (PDF).

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Impact of Accelerated Stress Tests on High Temperature PEMFC Degradation

Cited by 53 publications

References 24 publications

The Effect of Potential Cycling on High Temperature PEM Fuel Cell with Different Flow Field Designs

The Effect of Potential Cycling on High Temperature PEM Fuel Cell with Different Flow Field Designs

Long-Term Durability of PBI-Based HT-PEM Fuel Cells: Effect of Operating Parameters

Nonprecious Bimetallic Iron–Molybdenum Sulfide Electrocatalysts for the Hydrogen Evolution Reaction in Proton Exchange Membrane Electrolyzers

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