Performance of PEM Fuel Cells at Sub-Freezing Temperatures

Kim, Yu Seung; Rockward, Tommy; Davey, John; Pivovar, Bryan S.; Hussey, Daniel S.; Jacobson, David L.; Arif, Muhammad; Borup, Rod L.

doi:10.1149/1.2780967

Cited by 42 publications

(37 citation statements)

References 4 publications

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“…Dry H 2 and dry air (at 500 cc min -1 ) were then introduced into the anode and cathode of the cells and their ECS Transactions, 16 (2) 1939-1950 (2008) performance was monitored isothermally at sub freezing temperatures at various constant current densities. Cyclic voltammograms were obtained before and after the application of current and were used to determine the electrochemical catalyst surface area (H2 desorption peak) 3,8 . AC impedance spectra or HFR measurements were performed during the sub-freezing operation to illustrate the origin of the voltage loss.…”

Section: Fuel Cell Testingmentioning

confidence: 99%

“…Therefore the land water content represents the water from the MEA components in the middle (≈ 80%) of the land area and the channel water content represents the water from the middle (≈ 80%) of the anode and cathode flow channels and the MEA components in-between. The images collected at sub-freezing temperatures were averaged over 5 seconds (to reduce noise) and their water/ice content determined with respect to the dry image (at the same temperature) using Beer-Lambert's law 3,10 .…”

Section: Neutron Imagingmentioning

confidence: 99%

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Performance and Durability of PEM Fuel Cells Operated at Sub-Freezing Temperatures

et al. 2008

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The effect of MEA preparation on the performance of single-PEM fuel cells operated at sub-freezing temperatures is presented. The cell performance and durability are dependent on the MEA and are probably influenced by the porosity of the catalyst layers. When a cell is operated isothermally at -10 o C in constant current mode, the voltage gradually decreases over time and eventually drops to zero. AC impedance analysis indicated that the rate of voltage loss is initially due to an increase in the charge transfer resistance and is gradual. After a period, the rate of decay accelerates rapidly due to mass transport limitations at the catalyst and/or gas diffusion layers. The high frequency resistance also increases over time during the isothermal operation at sub-freezing temperatures and was a function of the initial membrane water content. LANL prepared MEAs showed very little loss in the catalyst surface area with multiple sub-freezing operations, whereas the commercial MEAs exhibited significant loss in cathode surface area with the anode being unaffected. These results indicate that catalyst layer ice formation is influenced strongly by the MEA and is responsible for the long-term degradation of fuel cells operated at sub-freezing temperatures. This ice formation was monitored using neutron radiography and was found to be concentrated near cell edges at the flow field turns.

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Section: Fuel Cell Testingmentioning

confidence: 99%

Section: Neutron Imagingmentioning

confidence: 99%

Performance and Durability of PEM Fuel Cells Operated at Sub-Freezing Temperatures

et al. 2008

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“…Raising the residual water content in the MEA also avoided an increase in the concentration overpotential. It is inferred from this result that the freezing of the residual water does not have the effect of destroying the structure of the GDL and the CL, as has been thought previously (6). The influence of the residual water content will be considered in a later section, taking into account the measured results for the pore size distribution in the MEA.…”

Section: Current Generation Characteristics Of Frozen Mea At Startupmentioning

confidence: 58%

Effect of Residual Water Contents in MEA on Performance Degradation Caused by Repeated Startup of Frozen Cell in PEFCs

et al. 2009

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The effect of residual water content in the MEA on performance degradation caused by repeated startup of a frozen cell at -30°C was investigated. The results indicated that in case the residual water content in the MEA was low, a condition occurred in which both diffusive and electrochemical activation capability of the ionomer in the catalyst layer of the cathode significantly declined and performance degradation increased compared with the high residual water content. Significant functional decay of the polymer electrolyte membrane was not measured. Presumably, dry operation of the cell during startup from a frozen state caused the decline in ionomer performance, resulting in degraded cell performance.

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“…1 The fuel cell tested was a 50 cm 2 cell assembled with the same types of MEA and GDLs described above. HFR measurements were made every second during the neutron imaging.…”

Section: Neutron Imagingmentioning

confidence: 99%

Water Dynamics in a PEM Fuel Cell: Effect of Current and Humidity Transients

Davey¹,

Spendelow²,

Hussey³

et al. 2008

ECS Trans.

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The water dynamics of the membrane electrode assembly (MEA) of a 50 cm 2 polymer electrolyte membrane (PEM) fuel cell was studied in response to current and humidity step transients as a function of inlet relative humidity (RH) and cell operating temperature. MEA water content change was monitored by high frequency resistance (HFR) and in situ neutron imaging.The MEA "wetting" response was significantly faster (10-30 seconds) than the reciprocal "drying" response (several minutes). The wetting response to increasing current appears faster than that to increasing gas inlet RH. Wetting and drying responses to gas inlet RH transients are greater at low current densities showing the dominating effect of current wetting over gas inlet humidity effects. Operating the fuel cell at 40 o C with no inlet gas humidification, a current wetting response was observed and 34 amps of current sustained. This showed that reaction water produced at the cathode is sufficient to support high current density if the drying effect of inlet gases is low. It also suggests that back diffusion of reaction water to the MEA is sufficient to account for the fast drop in HFR.In situ neutron imaging results show that GDL wetting is also faster than drying but on a slower time scale than that for the MEA. However, MEA and GDL drying are on a similar slow time scale and are coupled because water diffusing out of the MEA must move through the GDLs.

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Performance of PEM Fuel Cells at Sub-Freezing Temperatures

Cited by 42 publications

References 4 publications

Performance and Durability of PEM Fuel Cells Operated at Sub-Freezing Temperatures

Performance and Durability of PEM Fuel Cells Operated at Sub-Freezing Temperatures

Effect of Residual Water Contents in MEA on Performance Degradation Caused by Repeated Startup of Frozen Cell in PEFCs

Water Dynamics in a PEM Fuel Cell: Effect of Current and Humidity Transients

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