Evaluation of cathode contamination with Ca2+ in proton exchange membrane fuel cells

Qi, Jing; Ge, Junjie; Uddin, Aman; Zhai, Yunfeng; Pasaogullari, Ugur; St‐Pierre, Jean

doi:10.1016/j.electacta.2017.10.191

Cited by 16 publications

(5 citation statements)

References 39 publications

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“…24 and showed the IEC of the contaminated CCM is decreased by 58% compared to the as-received CCM as calcium cations replaced protons in the electrolyte. This is in agreement with the results presented by Qi et al 45 who measured the Ca 2+ exchange isotherms (cation uptake) for Nafion membranes soaked in cation solutions.…”

Section: Cell Testingsupporting

confidence: 93%

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

Banas

Uddin

Park

et al. 2018

J. Electrochem. Soc.

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Four hundred hour fuel cell tests were performed on commercial, as-received and Ca 2+ contaminated catalyst coated membranes (CCMs) to evaluate the effects of long term exposure of foreign cations on fuel cell performance and degradation. Following testing, significant thinning of the cathode catalyst layer was observed across the entire active area in the contaminated cell, while only localized thinning was observed in the as-received baseline CCM. Analysis of the elemental maps and line intensity profiles of platinum (Pt) obtained from energy dispersive X-ray spectrum (EDX) shows minimal change in total platinum content across the thickness of the catalyst layer, and hence loss of carbon is suspected to be the cause of the thinning. A numerical model is employed to show the foreign cation redistribution during testing, which shows proton depletion in the cathode catalyst layer when the CCM is contaminated with foreign cations. We hypothesize that this lack of protons leads to accelerated carbon corrosion in the cathode to supply protons to oxygen reduction where foreign cations block transport of protons. A carbon corrosion scheme is presented which shows that under the operating potentials of the cell, carbon oxidation can occur, leading to the observed thinning. The polymer electrolyte fuel cell (PEFC), a promising clean energy source for automobile application, still needs to overcome durability issues originating from various sources.1 Cationic impurities originated from either ambient air (e.g. roadside contaminants) or from the corrosion of stack and balance of plant components can significantly decrease the performance and life time of PEFCs. [1][2][3][4] In this paper, we report on the influence of foreign cationic contamination on the thinning of the cathode catalyst layer during non-accelerated testing. Long duration (400hr) testing was conducted using commercial catalyst coated membranes which showed significant catalyst layer thinning in a calcium cation contaminated cell, this thinning of the cathode catalyst layer was not observed in a non-contaminated baseline. While foreign cations are known to cause several degradation mechanisms in PEFCs, no study has examined the influence of cationic contamination on carbon corrosion, which we believe causes the thinning of the catalyst layer.To understand the impact and mechanism of cation contamination in PEFC, several modeling 5-11 and experimental studies 12-33 have been conducted, including ex-situ contamination of the polymer membrane with various cations before the test as well as injecting cations into the air or fuel stream during the cell test. Okada and co-workers extensively investigated the effect of various metal cations (Li + , Na + , Ca 2+ , Fe 2+ , Ni 2+ , Cu 2+ , Rb 2+ , Cs + ) on the transport properties of perfluorosulfonic acid (PFSA) membranes, thermodynamics and oxygen reduction reaction (ORR) kinetics. 5,[13][14][15][16][17][18] They reported that, with the exception of Li + , all foreign cations have higher affinity toward the sulfo...

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Section: Cell Testingsupporting

confidence: 93%

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

Banas

Uddin

Park

et al. 2018

J. Electrochem. Soc.

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“…It is expected that cation contaminants would have an even more pronounced effect on O 2 mass transfer because the O 2 permeability in ionomers is significantly diminished. ,− In contrast, the impact of organic contaminants on O 2 permeability in ionomers remains to be demonstrated and is expected because other ionomer properties are modified such as ionic conductivity …”

Section: Discussionmentioning

confidence: 99%

Contamination Mechanisms of Proton Exchange Membrane Fuel Cells - Mass Transfer Overpotential Origin

et al. 2020

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Several experimental methods were used to identify the cause of the concurrent increase in kinetic and mass transfer overpotentials during the contamination of proton exchange membrane fuel cells outfitted with a commercially relevant cathode catalyst loading of 0.1 mg Pt per cm2. Neutron images demonstrated that the transport of liquid water through gas diffusion electrode materials was subtly affected by the presence of propene and methyl methacrylate in air at ppm levels (25 to 100 ppm propene, 12.5 to 50 ppm methyl methacrylate). Multioxidant polarization curves were obtained to isolate overpotentials (O2, 21% O2 + 79% He, and air). For all cases, neat air, 50 ppm propene in air, and 25 ppm methyl methacrylate in air, only kinetic and mass transfer overpotentials increased (O2 reduction on a Pt supported on C catalyst, O2 diffusion through the catalyst layer ionomer). Also, only the O2 mass transfer coefficient associated with diffusion in the catalyst layer ionomer increased in the presence of 50 ppm propene and 25 ppm methyl methacrylate. Contaminant species adsorbed on the catalyst decrease the active surface area and increase both the real current density and the O2 reduction kinetic overpotential. The smaller active surface area also brings the real current density closer to the limiting value, inducing an increase of the mass transfer overpotential connected with O2 movement in the ionomer layer covering the catalyst. This mechanism was supported by a mathematical contamination model focused on contaminant and O2 processes on the catalyst surface (adsorption, reaction, desorption).

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“…One such technique for investigation of electrochemical kinetics, performance and durability of PEFC catalysts is testing using a rotating disk electrode (2,3). Among the topics in the literature, RDE analysis has been used to analyze oxygen reduction reaction kinetics (4,5), alternative non-PGM catalyst activity (6)(7)(8)(9), and catalyst response to contamination (10,11).…”

Section: Introductionmentioning

confidence: 99%

Manufacturing Process of Electrode Films

2020

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Rotating disk electrode (RDE) experiments form a key experimental characterization technique for measuring electrocatalyst performance and durability. While standard RDE testing protocols have been documented, it has been noted that catalyst film quality can skew measurements. The impact of relative humidity on drying is studied in an effort to produce consistent, high quality catalyst films for RDE experiments, which shows that high quality catalyst films can be manufactured repeatedly in a controlled environment, such as inside an environmental chamber as described.

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Evaluation of cathode contamination with Ca2+ in proton exchange membrane fuel cells

Cited by 16 publications

References 39 publications

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

Contamination Mechanisms of Proton Exchange Membrane Fuel Cells - Mass Transfer Overpotential Origin

Manufacturing Process of Electrode Films

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