Effects of Humidification on the Membrane Electrode Assembly of Proton Exchange Membrane Fuel Cells at Relatively High Cell Temperatures

Yin, Ken‐Ming; Chang, Chih-Ping

doi:10.1002/fuce.201100041

Cited by 12 publications

(6 citation statements)

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“…The Equation (4.13) predicts that the diameter is independent of the current density or gas diffusivity. The measured Nyquist plots reported in literature show that the diameter of this arc remains unchanged in different current densities [15,20,46,112,114,[183][184][185][186][187][188]190], temperatures [189], torques [66,112], humidification levels [20,189], cathode gas concentrations [34,184], flooding or dehydration conditions [24,91,106,182], starvation [189] and break-in process [112]. The impedance measurements presented in Section 4.3 also show that this arc remains unchanged in different operating temperatures, current densities and anode and cathode relative humidities.…”

Section: High Frequency Arcmentioning

confidence: 63%

“…The measured Nyquist plots of the PEM fuel cells in different operating conditions reported in literature include one arc [112,182], two distinguishable arcs [20,24,34,66,91,112,[183][184][185][186][187][188][189], or three clearly distinguishable arcs [15,20,46,114,190]. If the time constants of two adjacent arcs are close, they become convoluted and make one arc.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, the measured impedances in the literature prove this point: e.g., It has been shown [20,189] that when the relative humidity of the input gases increases drastically, the HFR clearly decreases (it has to be mentioned that for the measured impedances reported in Section 4.3, the change in HFR was not considerable as the relative humidity changes were not substantial). Another type of examples is the impedance measurements reported in [24,91,106,182] showing that HFR is larger when the cell is dehydrated and smaller in flooding cases. Also, it has been reported that the HFR decreases during the break-in process in which the membrane of a fuel cell stack is hydrated to achieve the peak performance [112].…”

Section: High Frequency Resistancementioning

confidence: 99%

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Process modeling of the impedance characteristics of proton exchange membrane fuel cells

Niya

Phillips

Hoorfar

2016

Electrochimica Acta

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The impedance characteristics of proton exchange membrane (PEM) fuel cells are studied and analyzed in this thesis. The modeling approaches presented in literature are thoroughly reviewed and categorized as the measurement-modeling and process-modeling approaches. In the former category, a hypothetical equivalent circuit which has the impedance characteristics similar to measured impedances is presented. Since the equivalent circuit is not directly resulted from the physical and chemical properties of the PEM fuel cells, the majority of the measurementmodeling approaches lead to dubious conclusions. In the process-modeling approach, on the other hand, the governing equations of the fuel cell must analytically be solved to determine and the impedance. However, a few process-modeling approaches presented in literature have shown to be indirectly based on the same assumptions as the measurement-modeling approach, and hence, those can also lead to similar conclusions. Therefore, these process-modeling approaches are referred to as the semi-process models here.In this thesis, the first complete process model for PEM fuel cells is presented which is not based on the above-mentioned assumptions. For each source of the losses in the fuel cell (i.e., the ohmic, activation and concentration overpotentials), a process model and equivalent circuit are obtained and compared against the impedance measurements reported in literature. The complete model (obtained by combining the models of the three losses) is then verified against the impedances measured in different operating conditions. Using the verified model, the measured Nyquist plots of the PEM fuel cells reported in literature are categorized. As a result, the dominant physical and chemical parameters controlling various arcs of the Nyquist plot are determined. Finally, the sensitivity analysis of the impedance characteristics of fuel cells is conducted using the verified model. As a result of this analysis, a minimum change in the operating conditions which results in statistically different Nyquist plots are determined.Finally, as an application of the model presented here, the impedance of the cell in the anode and cathode starvation modes are studied. It is shown that the anode starvation cannot be recognized from the impedance measurements, as predicted by the model. iii Preface This research was conducted in the Advanced Thermo-Fluidic Laboratory (ATFL) at University of British Columbia, Okanagan campus, under supervision of Dr. Mina Hoorfar. The results of this research have been published in several peer-reviewed journal articles and conference proceedings. Chapter 1 includes the discussions published as a review journal article (S.M. Rezaei Niya, M. Hoorfar (2013) 'Study of proton exchange membrane fuel cells using electrochemical impedance spectroscopy technique -A review ', Journal of Power Sources, Vol. 240, and also a journal article discussing the details of the process modeling approach (S.M. Rezaei Niya, M.Hoorfar (2015) 'Measurement, semi-process and pr...

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Section: High Frequency Arcmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: High Frequency Resistancementioning

confidence: 99%

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Process modeling of the impedance characteristics of proton exchange membrane fuel cells

Niya

Phillips

Hoorfar

2016

Electrochimica Acta

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“…To better understand hydration effects on durability, characterization of PEMs under liquid water saturation as an extreme exposure condition is necessary. The effect of hydration on the mechanical properties of PEMs has received extensive investigation [6][7][8][9][10][11][12][13][14]. Kusoglu et al [8] simulated the mechanical response of the membrane under humidity cycles and found that the membrane response strongly depends on the swelling anisotropy.…”

Section: Introductionmentioning

confidence: 99%

Mechanical properties and microstructure changes of proton exchange membrane under immersed conditions

Shi

Liú

Liu

et al. 2013

Polymer Engineering & Sci

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In this study, mechanical tensile stress–strain response and microstructure changes of proton exchange membranes (PEM) in immersed conditions are studied. The effects of water pretreatment and immersion time on stress–strain responses of Nafion®−212 membranes are discussed. It is found that in the water immersion it took 24 h for the membrane to reach saturation equilibrium. Compared with dry membrane, immersed Nafion membrane shows a lower stress level at 30°C, but a higher stress level at 70°C. In situ small angle neutron scattering (SANS) experiments show that with the increase of temperature and water uptake, domains of the membrane become ordered and stay stable at around 60°C. Based on the observation, the relationship between the microstructure and mechanical properties is explained. POLYM. ENG. SCI. 54:2215–2221, 2014. © 2013 Society of Plastics Engineers

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“…The deformable MEA, fabricated in a novel configuration, can be constrained in a limited space for both stationary and portable power sources [4][5][6][7]. One of the major design considerations is the water flooding in the MEA, arising from the blockage of gas diffusion layer by the generated water in cathode catalyst layer [8,9].…”

Section: Introductionmentioning

confidence: 99%

Mathematical Model of Proton Exchange Membrane Fuel Cell with Consideration of Water Management

Yin

Hsuen

2013

Fuel Cells

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One‐dimensional model on the membrane electrode assembly (MEA) of proton exchange membrane fuel cell is proposed, where the membrane hydration/dehydration and the possible water flooding of the respective cathode and anode gas diffusion layers are considered. A novel approach of phase‐equilibrium approximation is proposed to trace the water front and the detailed saturation profile once water emerges in either anode or cathode gas diffusion layer. The approach is validated by a semi‐analytical method published earlier. The novel approach is applicable to the polarization regime from open circuit voltage to the limiting current density under practical operation conditions. Oxygen diffusion is limited by water accumulation in the cathode gas diffusion layer as current increases, caused by excessive water generation at the cathode catalyst layer and the electro‐osmotic drag across the membrane. The existence of liquid water in the anode gas diffusion layer is predicted at low current densities if high degrees of humidification in both anode and cathode feeds are employed. The influences of inlet relative humidity, imposed pressure drop, and cell temperature are correlated well with the cell performance. In addition, the overpotentials attributed from individual components of the MEA are delineated against the cell current densities.

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Effects of Humidification on the Membrane Electrode Assembly of Proton Exchange Membrane Fuel Cells at Relatively High Cell Temperatures

Cited by 12 publications

References 50 publications

Process modeling of the impedance characteristics of proton exchange membrane fuel cells

Process modeling of the impedance characteristics of proton exchange membrane fuel cells

Mechanical properties and microstructure changes of proton exchange membrane under immersed conditions

Mathematical Model of Proton Exchange Membrane Fuel Cell with Consideration of Water Management

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