Dissolution and migration of platinum after long-term operation of a polymer electrolyte fuel cell under various conditions

Kim, Lim; Chung, Chul Goo; Sung, Yong Wook; Chung, Jong Shik

doi:10.1016/j.jpowsour.2008.05.062

Cited by 78 publications

(56 citation statements)

References 22 publications

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“…This observation is consistent with what was reported with long-term operation of PEMFC [14,15,18]: because of the moderate excess of hydrogen (20%) at the anode, Pt 2+ are reduced to platinum further from the cathode surface although only 20:80 (O 2 /N 2 ) was fed to the cathode.…”

Section: Phenomena In the Electrode Structuresupporting

confidence: 92%

“…For high cathode potentials, degradation phenomena can occur in the MEA, in particular degradation of the polymer electrolyte [10], corrosion of carbon in the electrode [11,12] and platinum dissolution [13][14][15]. In the present case, although the cathode potential is of the order of 500 mV the presence of ozone might allow the above phenomena to occur.…”

Section: Discussionmentioning

confidence: 72%

“…6 Cross-sectional SEM view of the cathode GDL: (a) new GDL and (b) after the fourth ozone injection. ment may dissolve from the active layer, then reducing the overall activity of the electrode catalyst as reported for other ageing operating conditions [14][15]18]. Sustained ozone injections may decompose the platinum clusters to a significant extent, while also corroding the carbon support of the electrode: the two oxidation reactions would then be to reduce irreversibly the electrode activity towards oxygen reduction.…”

Section: Phenomena In the Electrode Structurementioning

confidence: 88%

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Effects of Ozone on the Performance of a Polymer Electrolyte Membrane Fuel Cell

et al. 2009

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The effects of ozone at concentrations near 1000 vppm in air on the performance of a single polymer electrolyte membrane fuel cell (PEMFC) were investigated. Ozone was injected to the cathode alternately with far longer operation periods at 0.54 A cm–2 with ozone‐free air. Impedance spectra were recorded before, during and after exposure to ozone. After the first ozone injection, the loss in voltage was reversible, so were the changes in the resistances of the cell. Subsequent injection periods damaged irreversibly the PEMFC assembly. TEM observations with energy dispersive X‐ray spectroscopy analysis of the various parts of the PEMFC assembly together with the variations of the resistances allowed the ageing mechanism to be highlighted. Ozone was shown to allow partial dissolution of the Pt of the cathode catalyst. The charge transfer resistance was noticeably increased accordingly. Platinum re‐precipitated in the membrane bulk, and was also observed in the cathode‐side GDL. In addition, the likely degradation of the polymer near the triple‐point in the cathode could hinder gas solubility and water removal, as indicated by larger diffusion resistances.

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Section: Phenomena In the Electrode Structuresupporting

confidence: 92%

Section: Discussionmentioning

confidence: 72%

Section: Phenomena In the Electrode Structurementioning

confidence: 88%

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Effects of Ozone on the Performance of a Polymer Electrolyte Membrane Fuel Cell

et al. 2009

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“…Moreover, dissolved platinum ions can migrate into the electrolyte membrane. To our knowledge, the presence of platinum in the membrane has first been observed by Aragane et al [15], and the formation of precipitations was studied in more detail in follow up publications [16][17][18][19][20] by several authors. In addition to the loss of electrochemically active catalyst also the resistance of the MEA is likely to be affected by the formation of precipitates in the membrane [20].…”

Section: Introductionmentioning

confidence: 90%

Dissolution and Migration of Platinum in PEMFCs Investigated for Start/Stop Cycling and High Potential Degradation

et al. 2011

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Dissolution and migration of platinum due to start/stop degradation and increased cathode potentials were studied for commercial membrane electrode assemblies (MEA). The chosen conditions closely mimic real situations in automotive operation. In start/stop tests, we observed a strongly enhanced platinum dissolution due to the dynamic interplay of repeated cell start‐up and consecutive normal fuel cell operation, which is related to platinum oxidation (start‐up) and reduction (normal operation) cycles. Consequently, the performed test protocols distinguish between dynamic and static load profiles. Electrochemical investigations before and after degradation monitor the loss in cell performance. Since electron microscopy offers the unique possibility to unravel and distinguish degradation due to carbon corrosion and agglomeration or platinum dissolution, a focus was set on this method. For the start/stop MEA pronounced platinum dissolution accompanied by the formation of large platinum precipitations in the membrane was found. Carbon corrosion was also observed, but did not lead to a significantly reduced porosity and loss in platinum dispersion. In contrast, the MEA which was exposed to high constant potentials exhibited severe damage to the 3D cathode structure due to carbon corrosion. However, no pronounced platinum dissolution was observed and only few Pt precipitations were found in the membrane itself.

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“…A lot of effort has been spent on replacing Pt by less expensive, non-precious metal alternatives [3][4][5], but so far largely to no avail. Moreover, although platinum is comparatively stable in the harsh conditions of a PEM-FC, still a not negligible fraction of the platinum is leached out off the electrode and dragged into the membrane [6][7][8][9]. There it can re-precipitate and form huge crystals, which are no longer active in catalyzing the electrode reactions and thus lost for the fuel cell performance.…”

Section: Introductionmentioning

confidence: 99%

The use of in situ X-ray absorption spectroscopy in applied fuel cell research

et al. 2009

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For a detailed understanding and systematic optimization of fuel cell systems, in situ studies are an indispensable tool, as they provide information on the catalyst structure in different operation conditions. X-ray absorption spectroscopy (XAS) is in particular suitable for operando investigations, since it does not require ultra high vacuum conditions or long-range order in the sample. Furthermore, it provides in situ information on oxidation state, adsorbed species and catalyst structure, and thus complements ex situ information, e.g. from X-ray diffraction (structure), X-ray photoelectron spectroscopy (oxidation state) and FTIR (adsorbates) nicely. In a spectroelectrochemistry experiment, XAS can be combined with different electrochemical techniques in order to satisfy different needs and scientific aims. Spectra of both a Pt-Ru anode catalyst and a Pt-Co cathode catalyst were recorded at different potentials, while measuring the current-potential characteristics of a single cell. So-called half-cell measurements, where the former fuel cell cathode was used with hydrogen as the reference electrode, were performed in water and ethanol to obtain a more detailed mechanistic insight into the ethanol electrooxidation. From a more industrial point of view, different catalysts were tested with a fast potential cycling protocol simulating rapid load changes in a vehicle

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Dissolution and migration of platinum after long-term operation of a polymer electrolyte fuel cell under various conditions

Cited by 78 publications

References 22 publications

Effects of Ozone on the Performance of a Polymer Electrolyte Membrane Fuel Cell

Effects of Ozone on the Performance of a Polymer Electrolyte Membrane Fuel Cell

Dissolution and Migration of Platinum in PEMFCs Investigated for Start/Stop Cycling and High Potential Degradation

The use of in situ X-ray absorption spectroscopy in applied fuel cell research

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