Anion-exchange membranes in electrochemical energy systems

Varcoe, John R.; Atanassov, Plamen; Dekel, Dario R.; Herring, Andrew M.; Hickner, Michael A.; Kohl, PA Paul; Kucernak, A; Mustain, William E.; Nijmeijer, DC Kitty; Scott, Keith; Xu, Tongwen; Zhuang, Lin

doi:10.1039/c4ee01303d

Cited by 1,739 publications

(1,583 citation statements)

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“…After the voltage stabilizes, the current further increases and peaks at 2.1 A cm À2 before starting to decline. The increase in cell current to 2.1 A cm À2 coupled with the change in cell potential facilitates the "self-purging" phenomena that is known to occur through an increased generation of OH À at the cathode and flux of OH À ions to the anode [1,31,34]. The (bi)carbonate self-purging during startup was observed by passing the anode effluent through a nondispersive infrared CO 2 detector (PP Systems SBA-5).…”

Section: Cell Operation and Response During Start-up/break-inmentioning

confidence: 99%

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Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

Omasta

Wang

Peng

et al. 2018

Journal of Power Sources

249

239

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Section: Cell Operation and Response During Start-up/break-inmentioning

confidence: 99%

“…The resulting intermediate ETFE-gpoly(VBC) films were subsequently dried at 70 C for 5 h in a vacuum oven to remove all traces of solvent. The gravimetric degree of grafting (DoG, %) of the intermediate membranes was calculated using Equation (1).…”

Section: Tj Omasta Et Al / Journal Of Power Sources XXX (2017) 1e9mentioning

confidence: 99%

Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

Omasta

Wang

Peng

et al. 2018

Journal of Power Sources

249

239

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“…16 However, AEMFCs still suffer a decline in performance due to bicarbonate/carbonate formation in the membrane and catalyst layers (CLs) leading to additional ohmic and kinetic losses. [13][14][15] In an AEMFC, the following electrochemical reactions occur in the CLs as follows:Net :Hydrogen combines with hydroxide ions to produce water in the anode. Oxygen reacts with water to generate hydroxide ions in the cathode.…”

mentioning

confidence: 99%

Elucidating Performance Limitations in Alkaline-Exchange- Membrane Fuel Cells

Shiau

Zenyuk

Weber

2017

J. Electrochem. Soc.

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Water management is a serious concern for alkaline-exchange-membrane fuel cells (AEMFCs) because water is a reactant in the alkaline oxygen-reduction reaction and hydroxide conduction in alkaline-exchange membranes is highly hydration dependent. In this paper, we develop and use a multiphysics, multiphase model to explore water management in AEMFCs. We demonstrate that the low performance is mostly caused by extremely non-uniform distribution of water in the ionomer phase. A sensitivity analysis of design parameters including humidification strategies, membrane properties, and water transport resistance was undertaken to explore possible optimization strategies. Furthermore, the strategy and issues of reducing bicarbonate/carbonate buildup in the membrane-electrode assembly with CO 2 from air is demonstrated based on the model prediction. Overall, mathematical modeling is used to explore trends and strategies to overcome performance bottlenecks and help enable AEMFC commercialization. Among existing fuel-cell types, alkaline-exchange-membrane fuel cells (AEMFCs) or hydroxide-exchange-membrane fuel cells (HEMFCs) have intriguing features as compared to proton-exchangemembrane fuel cells (PEMFCs). Their advantage is mainly the possibility of using non-noble catalysts due to faster oxygenreduction-reaction (ORR) kinetics in alkaline media than in acidic media 1-4 as well as perhaps the use of less expensive hydrocarbon membranes. Disadvantages of AEMFCs include lower hydrogenoxidation-reaction (HOR) kinetics, more complicated water management, and lower intrinsic conductivity for hydroxide compared to proton transport. [5][6][7][8][9][10][11][12][13] In addition, CO 2 in the air reacts with hydroxide ions to form bicarbonate and carbonate ions, possibly hindering the terrestrial development of AEMFCs by removing hydroxide available for HOR and further limiting hydroxide conductivity. 14,15 Compared to conventional alkaline fuel cells (i.e., using a liquid electrolyte of potassium hydroxide), AEMFCs use a polymeric membrane and should have better tolerance for CO 2 because the precipitate K 2 CO 3 is absent in the AEMFC due to the lack of mobile cations in the membrane. 16 However, AEMFCs still suffer a decline in performance due to bicarbonate/carbonate formation in the membrane and catalyst layers (CLs) leading to additional ohmic and kinetic losses. [13][14][15] In an AEMFC, the following electrochemical reactions occur in the CLs as follows:Net :Hydrogen combines with hydroxide ions to produce water in the anode. Oxygen reacts with water to generate hydroxide ions in the cathode. Along with the transport of ions from cathode to anode, electro-osmosis moves water from cathode to anode. As shown in the reactions, AEMFCs are expected to have more complicated water management. Water production by the HOR and electro-osmosis may cause flooding in the anode. Since water is a stoichiometric reactant at the cathode, dehydration may occur and limit ORR kinetics as well as ionic conduction in the membrane and cathode CL, ...

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“…From at hermodynamic point of view,c arbon is only stable for very small potentialr anges in water. [88] For example, under standard conditions, the four-electron oxidation of Ct oC O 2 could occur at E % + 200 mV,w hich is far below the thermodynamic potential for water oxidation. However, the reaction is very much hindered owing to the mechanistically very complex transformation of elemental, graphitic carbon to carbon dioxide.…”

Section: Electrocatalytic Properties Of Mno X /C Anodesmentioning

confidence: 99%

Electrocatalytic Water Oxidation by MnO_x/C: In Situ Catalyst Formation, Carbon Substrate Variations, and Direct O₂/CO₂ Monitoring by Membrane‐Inlet Mass Spectrometry

et al. 2017

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Layers of amorphous manganese oxides were directly formed on the surfaces of different carbon materials by exposing the carbon to aqueous solutions of permanganate (MnO4−) followed by sintering at 100–400 °C. During electrochemical measurements in neutral aqueous buffer, nearly all of the MnOx/C electrodes show significant oxidation currents at potentials relevant for the oxygen evolution reaction (OER). However, by combining electrolysis with product detection by using mass spectrometry, it was found that these currents were only strictly linked to water oxidation if MnOx was deposited on graphitic carbon materials (faradaic O2 yields >90 %). On the contrary, supports containing sp3‐C were found to be unsuitable as the OER is accompanied by carbon corrosion to CO2. Thus, choosing the “right” carbon material is crucial for the preparation of stable and efficient MnOx/C anodes for water oxidation catalysis. For MnOx on graphitic substrates, current densities of >1 mA cm−2 at η=540 mV could be maintained for at least 16 h of continuous operation at pH 7 (very good values for electrodes containing only abundant elements such as C, O, and Mn) and post‐operando measurements proved the integrity of both the catalyst coating and the underlying carbon at OER conditions.

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Anion-exchange membranes in electrochemical energy systems

Abstract: A detailed perspective on the use of anion-exchange membranes in fuel cells, electrolysers, flow batteries, reverse electrodialysis, and bioelectrochemical systems.

Cited by 1,739 publications

References 813 publications

Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

Elucidating Performance Limitations in Alkaline-Exchange- Membrane Fuel Cells

Electrocatalytic Water Oxidation by MnO_x/C: In Situ Catalyst Formation, Carbon Substrate Variations, and Direct O₂/CO₂ Monitoring by Membrane‐Inlet Mass Spectrometry

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Anion-exchange membranes in electrochemical energy systems

Abstract: A detailed perspective on the use of anion-exchange membranes in fuel cells, electrolysers, flow batteries, reverse electrodialysis, and bioelectrochemical systems.

Cited by 1,739 publications

References 813 publications

Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

Elucidating Performance Limitations in Alkaline-Exchange- Membrane Fuel Cells

Electrocatalytic Water Oxidation by MnOx/C: In Situ Catalyst Formation, Carbon Substrate Variations, and Direct O2/CO2 Monitoring by Membrane‐Inlet Mass Spectrometry

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Product

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Electrocatalytic Water Oxidation by MnO_x/C: In Situ Catalyst Formation, Carbon Substrate Variations, and Direct O₂/CO₂ Monitoring by Membrane‐Inlet Mass Spectrometry