The interaction of water vapors with H3PO4 imbibed electrolyte based on PBI/polysulfone copolymer blends

Daletou, Maria K.; Kallitsis, Joannis K.; Voyiatzis, George A.; Neophytides, Stylianos G.

doi:10.1016/j.memsci.2008.09.040

Cited by 89 publications

(73 citation statements)

References 30 publications

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“…Reformate conditions Even though HT-PEMFCs have the advantage of working efficiently under anhydrous conditions compared to LT-PEMFCs, humidification still improves the performance by increasing the proton conductivity of the polymer membrane [8]. Water also hydrates phosphoric acid (PA) and ensures a more uniform distribution of PA, thereby reducing PA poisoning effect which happens when PA and H 2 reduced polyphosphoric acid species block Pt surface area [28].…”

Section: Dry Hydrogen Operationmentioning

confidence: 99%

Electrochemical Impedance Spectroscopy (EIS) Characterization of Reformate-operated High Temperature PEM Fuel Cell Stack

Sahlin

Araya

Andreasen³

et al. 2017

IJPER

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This paper presents an experimental characterization of a high temperature proton exchange membrane fuel cell (HT-PEMFC) short stack carried out by means of impedance spectroscopy. Selected operating parameters; temperature, stoichiometry and reactant compositions were varied to investigate their effects on a reformate-operated stack. Polarization curves were also recorded to complement the impedance analysis of the researched phenomena. An equivalent circuit model was used to estimate the different resistances at varying parameters. It showed a significantly higher low frequency resistance at lower stoichiometry. Both anode and cathode stoichiometric ratio had significant effects on the stack performance during the dry hydrogen and reformate operation modes. In both cases the effects faded away when sufficient mass transport was achieved, which took place at λ anode = 1.3 for dry hydrogen, λ anode = 1.6 for reformate operation and λ cathode = 4. The work also compared dry hydrogen, steam reforming and autothermal reforming gas feeds at 160• C and showed appreciably lower performance in the case of autothermal reforming at the same stoichiometry, mainly attributable to mass transport related issues. In a CO poisoning analysis the stack showed good tolerance to concentration up to 1% CO in the fuel stream.

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Section: Dry Hydrogen Operationmentioning

confidence: 99%

Electrochemical Impedance Spectroscopy (EIS) Characterization of Reformate-operated High Temperature PEM Fuel Cell Stack

Sahlin

Araya

Andreasen³

et al. 2017

IJPER

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“…This type of polymer material is composed of an aromatic polyether backbone containing mainly chain polar pyridine moieties and that can be doped with phosphoric acid. When the phosphoric acid binds with and is retained in the membrane matrix [63], these materials have a high glass transition temperatures (approximately 270 • C) and high thermal stability [64]. Acid doping levels are normally well above 100% which results in membrane conductivity of 0.05 S/cm and free acid which must be managed in a similar manner as was defined in the PBI discussion.…”

Section: High Temperature Polymer Electrolyte Membranesmentioning

confidence: 99%

Catalyst, Membrane, Free Electrolyte Challenges, and Pathways to Resolutions in High Temperature Polymer Electrolyte Membrane Fuel Cells

2017

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High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are being studied due to a number of benefits offered versus their low temperature counterparts, including co-generation of heat and power, high tolerance to fuel impurities, and simpler system design. Approximately 90% of the literature on HT-PEM is related to the electrolyte and, for the most part, these electrolytes all use free phosphoric acid, or similar free acid, as the ion conductor. A major issue with using phosphoric acid based electrolytes is the free acid in the electrodes. The presence of the acid on the catalyst sites leads to poor oxygen activity, low solubility/diffusion, and can block electrochemical sites through phosphate adsorption. This review will focus on these issues and the steps that have been taken to alleviate these obstacles. The intention is this review may then serve as a tool for finding a solution path in the community.

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“…At each operating temperature several tests were done with humidified gas streams at two different dew points, ~32 °C and ~50 °C which correspond to water partial pressures of ~4.7 and ~12 kPa, respectively. These dew points were chosen because according to [16] water partial pressure equilibriums for the dimerization of the 85 wt.% phosphoric acid in the PBI are 5.4 and 10 kPa at the 150 and 170 °C, respectively. All tests at the aforementioned set points were completed with cathode stream humidified first.…”

Section: Water Transport Coefficientmentioning

confidence: 99%

“…Dilution is caused by the permeation of nitrogen and water molecules from the cathode. With nitrogen permeation through the membrane reportedly being very low [16], water build-up on the anode could be the main reason behind the necessity of a purge. It is therefore important to investigate the effects of water vapor on the cell's performance.…”

Section: Introductionmentioning

confidence: 99%

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Water transport study in a high temperature proton exchange membrane fuel cell stack

Bezmalinović

Strahl

Roda

et al. 2014

International Journal of Hydrogen Energy

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A study of water transport in a high temperature phosphoric acid doped polybenzimidazole (PBI) membrane fuel cell stack is reported. Tests with different stoichiometries of dry cathode and different humidity levels of anode are performed. It is found that water transport across the membrane electrode assembly (MEA) is noteworthy and that water vapor partial pressure on the anode outlet is almost always higher than on the cathode outlet, even when using dry hydrogen. The water transport is a strong function of current density but it also depends on stoichiometry and humidity level. In a series of tests with dry nitrogen on one side and humid nitrogen on the other side, the membrane's water permeability coefficient is determined to be 2.4x10 -13 mol s -1 cm -1 Pa -1 at 160 °C which is more than an order of magnitude higher than the values previously reported in the literature. Also, the results indicate that the permeability coefficient might be relative humidity dependent and could even be somewhat higher than the value reported here, but further investigation is needed. The experimental findings are reproduced and explained with a 2D steady state computational fluid dynamics (CFD) model. Internal water transport profiles across the membrane and along the gas flow channels are presented and discussed.

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The interaction of water vapors with H3PO4 imbibed electrolyte based on PBI/polysulfone copolymer blends

Cited by 89 publications

References 30 publications

Electrochemical Impedance Spectroscopy (EIS) Characterization of Reformate-operated High Temperature PEM Fuel Cell Stack

Electrochemical Impedance Spectroscopy (EIS) Characterization of Reformate-operated High Temperature PEM Fuel Cell Stack

Catalyst, Membrane, Free Electrolyte Challenges, and Pathways to Resolutions in High Temperature Polymer Electrolyte Membrane Fuel Cells

Water transport study in a high temperature proton exchange membrane fuel cell stack

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