Physical and chemical modification routes leading to improved mechanical properties of perfluorosulfonic acid membranes for PEM fuel cells

Subianto, Surya; Pica, Monica; Casciola, Mario; Cojocaru, Paula; Merlo, Luca; Hards, Graham; Jones, Deborah J.

doi:10.1016/j.jpowsour.2012.12.121

Cited by 156 publications

(99 citation statements)

References 128 publications

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“…Crosslinking is another common technique to improve membrane strength. 4,22 Chemically crosslinking polymer chains increases the modulus and strength, however the method of crosslinking may reduce the ionic concentration and a high degree of crosslinking may cause membrane embrittlement. Physical reinforcement of membranes with a nonconductive, porous polymer film can also significantly improve durability, as long as it is also chemically stable to hydroxide.…”

Section: H678mentioning

confidence: 99%

“…23 Porous polytetrafluoroethylene (PTFE) membranes and fibers have been incorporated into PFSAs to improve mechanical durability. 3,4,24 Reinforcing an ion exchange membrane also helps resist dimensional swelling, increasing stability between dry and hydrated states and prolonging membrane lifetime. 6,16 While physical reinforcement can strengthen the membrane and resist changes with hydration, the addition of a nonconductive material lowers the ion exchange capacity of the membrane.…”

Section: H678mentioning

confidence: 99%

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Mechanical Characterization of Anion Exchange Membranes by Extensional Rheology under Controlled Hydration

Vandiver

Caire

Carver

et al. 2014

J. Electrochem. Soc.

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Alkali anion exchange membrane (AEM) based devices have the potential for electrochemical energy conversion using inexpensive catalysts and a variety of fuel types. Membrane stability and anion transport must be improved in AEMs before these devices can be fully realized. Mechanical failure of the membrane can contribute to failure of the device, thus membrane durability is critical to overall system design. Here, a study of the mechanical properties of three well-established AEMs uses a modified extensional rheometer platform to simulate tensile testing using small membrane samples. Mechanical properties were tested at 30 and 60 • C under dry or water saturated gas conditions. Water in the membrane has a plasticizing effect, softening the membrane and reducing strength. PEEK membrane reinforcement limits swelling producing negligible softening and only a 9% decrease in strength from dry to hydrated conditions at 30 • C. Higher cation concentration increases water uptake resulting in significant softening, a 57% reduction in Young's modulus, and a 67% reduction in strength when hydrated at 30 • C. In a working electrochemical device, AEMs must maintain integrity over a range of temperatures and hydrations, making it critical to considering mechanical properties when designing new membranes. Polymer electrolyte membrane fuel cells and electrolyzers are potentially disruptive technologies that will replace traditional heat engines such as internal combustion engines for transportation applications, portable electronics, and are scalable to larger energy storage facilities. Polymer electrolyte membrane fuel cells are suitable for transportation applications due to their low temperature start-up and operation, high power density, and quick refueling.1-3 Proton exchange membranes (PEMs) have dominated polymer electrolyte membrane fuel cell development in the last several decades, resulting in the development of relatively stable, well performing membranes.1-4 Current PEM fuel cells remain cost prohibitive due to high catalysts costs, as well as long-term durability issues. 3,5,6 Anion exchange membranes (AEMs) can also be utilized in polymer electrolyte membrane devices and have several potential benefits over PEMs. AEM fuel cells benefit from increased kinetics in an alkali media allowing more complex fuels then hydrogen and have the potential to utilize non-platinum catalysts to reduce costs. 7-11However, a number of challenges must be overcome before AEMs reach the performance and durability necessary for fuel cells and other electrochemical energy conversion devices. Hydroxide present in the AEM degrades many of the proposed cationic groups and some polymer backbones, making development of chemically stable AEMs difficult. 9,11,12 Additionally, transport of hydroxide in AEMs is inherently slower than protons in PEMs, 13 to compensate, the concentration of ionic groups is often increased in AEMs.8 Increasing ion concentration in AEMs increases water sorption in the polymer and can result in significant dimensional...

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Section: H678mentioning

confidence: 99%

Section: H678mentioning

confidence: 99%

Mechanical Characterization of Anion Exchange Membranes by Extensional Rheology under Controlled Hydration

Vandiver

Caire

Carver

et al. 2014

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…4,5 While PEM fuel cells have been widely researched and developed over the last few decades, anion exchange membrane (AEM) fuel cells offer potential advantages over PEMs. [6][7][8][9][10] The alkali nature of an AEM fuel cell allows redox reactions with nonplatinum catalysts and improves oxygen reduction kinetics.…”

mentioning

confidence: 99%

Mechanical Performance of Polyiosoprene Copolymer Anion Exchange Membranes by Varying Crosslinking Methods

Vandiver

Caire

Ertem

et al. 2015

J. Electrochem. Soc.

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Anion exchange membranes (AEM) are polymer electrolytes that facilitate ion transport in alkaline fuel cells and electrochemical devices. Fabrication of mechanically durable AEMs with high ionic conductivity is a challenge. Here, a copolymer of isoprene and vinylbenzyl trimethylammonium and a terpolymer of isoprene, vinylbenzyl trimethylammonium and styrene were crosslinked by various methods, and properties, including conductivity and mechanical strength, were investigated at dry and saturated conditions. Polymer chemistry and degree of crosslinking significantly influenced conductivity, swelling, and mechanical properties. The terpolymer had a higher proportion of vinylbenzyl trimethylammonium units increasing the ion exchange capacity (IEC), but membranes could still be rendered insoluble by crosslinking. The higher IEC of the terpolymer resulted in higher chloride conductivity, 20-75 mS/cm at 50 • C and 95%RH, compared to 4-17 mS/cm for the copolymer at the same conditions. At dry conditions films were stiff, having Young's moduli between 100-740 MPa, but hydration caused severe softening, reducing moduli by 1-2 orders of magnitude. The severe softening effect of hydration was confirmed by dynamic mechanical analysis. The AEMs studied did not have adequate mechanical durability at hydrated conditions, additional work is needed to determine polymer chemistries and crosslinking methods that will produce robust AEMs for long-term use in fuel cells and electrochemical devices. Fuel cells are attractive energy conversion devices that utilize hydrogen to produce electrical energy for stationary and transportation applications, with the by-product being water.1,2 Electrolyzers utilize a similar principle to produce hydrogen from water using electrical energy. Fuel cells and electrolyzers both utilize a polymer electrolyte membrane to separate the catalyst layers and efficiently transport ions, while limiting crossover of other species.1,3 Proton exchange membranes (PEM), specifically perfluorosulfonic acid polymers such as Nafion, have been utilized almost exclusively for current fuel cells, owing to their high proton conductivity and suitable chemical and mechanical stability. 4,5 While PEM fuel cells have been widely researched and developed over the last few decades, anion exchange membrane (AEM) fuel cells offer potential advantages over PEMs. [6][7][8][9][10] The alkali nature of an AEM fuel cell allows redox reactions with nonplatinum catalysts and improves oxygen reduction kinetics. 6,9,10 On going research seeks to develop robust, well performing AEMs for use in fuel cells, electrolyzers, and other electrochemical devices.Anion exchange membranes must have a high ionic conductivity and be chemically and mechanically stable over the life-time of the fuel cell.6,9,10 Chemical stability is a concern in AEMs as hydroxide ions present in the membrane have the potential to degrade the polymer backbone and cation functionalities. 6,11,12 Hydroxide transport is inherently slower than proton transport, to compensate...

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“…In the case of Nafion ® MEAs the effect is smaller, but also clearly evidenced, and this is consistent with the smaller water retention inside the electrode provided by the incorporated Nafion-ionomer. 13 Effects of cell temperature for Nafion ® and Aquivion ® MEAs…”

Section: Physical Characterization Of the Electrocatalystsmentioning

confidence: 99%

“…In this context, within the last decade, a new membrane, conceptually similar Nafion ® had been developed (Aquivion ® , Solvay), but containing shorter fluorocarbon chains, which result in high polymer crystallinity and hydrophilicity and thus high thermal stability and mechanical strength. 13,14 In fact, previous works have shown that when applied to PEMFC with pure H 2 /O 2 reactants, the Aquivion ® membrane had provided quite impressive performances for the PEMFC working at temperatures up to 130 °C, [15][16][17][18] this being a quite relevant fact when the CO tolerance issue is considered. The advantages of employing Aquivion ® membranes have been also demonstrated on intermediate temperature PEM water electrolyzer systems.…”

Section: Introductionmentioning

confidence: 99%

CO Tolerance and Stability of Proton Exchange Membrane Fuel Cells with Nafion® and Aquivion® Membranes and Mo‑Based Anode Electrocatalysts

Iezzi¹,

Santos²,

Silva³

et al. 2017

J. Braz. Chem. Soc.

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This work presents a CO tolerance study of PtMo/C (70:30, Pt:Mo) and Pt/MoO 2 -C anode catalysts on proton exchange membrane fuel cells (PEMFC) with Nafion ® and Aquivion ® ionomer membranes. Results denote improved activity for the hydrogen oxidation reaction (HOR) in the presence of CO on both anode catalysts at 85 °C. Experiments of identical location transmission electron microscopy evidenced very good stability of the Pt particles along an accelerate stress test (AST) applied to the Mo-based anode catalysts. However, a crossover of degradation Mo products originated in the anode and going to the cathode takes place along this anode AST, causing a PEMFC performance decay. A very little effect of the nature of the membrane, Nafion ® or Aquivion ® , is observed over these crossover phenomena. Results also denote that when operating at appropriate high temperatures (105 °C for Nafion ® and 125 °C for Aquivion ® ), there is no need of incorporating unstable oxophilic transition metals on Pt to achieve improved CO tolerance on PEMFCs, when the CO level in the hydrogen fed is of the order of 100 ppm.

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Physical and chemical modification routes leading to improved mechanical properties of perfluorosulfonic acid membranes for PEM fuel cells

Cited by 156 publications

References 128 publications

Mechanical Characterization of Anion Exchange Membranes by Extensional Rheology under Controlled Hydration

Mechanical Characterization of Anion Exchange Membranes by Extensional Rheology under Controlled Hydration

Mechanical Performance of Polyiosoprene Copolymer Anion Exchange Membranes by Varying Crosslinking Methods

CO Tolerance and Stability of Proton Exchange Membrane Fuel Cells with Nafion® and Aquivion® Membranes and Mo‑Based Anode Electrocatalysts

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