Oxygen reduction on platinum in mixtures of phosphoric and trifluoromethane sulphonic acids

Enayetullah, M. A.; O’Sullivan, E. J.; Yeager, Ernest

doi:10.1007/bf01016905

Cited by 14 publications

(10 citation statements)

References 4 publications

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“…In the early research on PAFC, alternative electrolytes have been extensively investigated [219][220][221][222]. Some perfluorinated acids are found to be able to enhance the kinetics but suffer from low conductivity in concentrated solutions, high vapour pressure, and flooding the PTFE bonded gas diffusion electrodes.…”

Section: Kinetics Of Oxygen Reductionmentioning

confidence: 99%

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Jensen

Savinell

et al. 2009

Progress in Polymer Science

1,243

852

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, acid-base polymer membranes represent an effective approach. The phosphoric acid-doped polybenzimidazole membrane seems so far the most successful system in the field. It has in recent years motivated extensive research activities with great progress. This treatise is devoted to updating the development, covering polymer synthesis, membrane casting, physicochemical characterizations and fuel cell technologies. To optimize the membrane properties, high molecular weight polymers with synthetically modified or N-substituted structures have been synthesized. Techniques for membrane casting from organic solutions and directly from acid solutions have been developed. Ionic and covalent cross-linking as well as inorganic-organic composites has been explored. Membrane characterizations have been made including spectroscopy, water uptake and acid doping, thermal and oxidative stability, conductivity, electro-osmotic water drag, methanol crossover, solubility and permeability of gases, and oxygen reduction kinetics. Related fuel cell technologies such as electrode and MEA fabrication have been developed and high temperature PEMFC has been successfully demonstrated at temperatures of up to 200• C under ambient pressure. No gas humidification is mandatory, which enables the elimination of the complicated humidification system, compared with Nafion cells. Other operating features of the PBI cell include easy control of air flow rate, cell temperature and cooling. The PBI cell operating at above 150• C can tolerate up to 1% CO and 10 ppm SO 2 in the fuel stream, allowing for simplification of the fuel processing system and possible integration of the fuel cell stack with fuel processing units. Long-term durability with a degradation rate of 5 V h −1 has been achieved under continuous operation with hydrogen and air at 150-160• C. With load or thermal cycling, a performance loss of 300 V per cycle or 40 V h −1 per operating hour was observed. Further improvement should be done by, e.g. optimizing the thermal and chemical stability of the polymer, acid-base interaction and acid management, activity and stability of catalyst and more importantly the catalyst support, as well as the integral interface between electrode and membrane.

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Section: Kinetics Of Oxygen Reductionmentioning

confidence: 99%

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Jensen

Savinell

et al. 2009

Progress in Polymer Science

1,243

852

View full text Add to dashboard Cite

show abstract

“…However, the data contain a significant spread, making correct quantification of O2 mass transport in HTPEMFCs difficult [13]. Furthermore, many research efforts are directed to additive-modified PA electrolytes that may improve the ORR for instance via changes in solubility and diffusivity of O2 or via a reduced specific adsorption [23,[27][28][29]. This draws ongoing interest in solubility and diffusivity data of PA-based electrolytes at elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of temperature and electrolyte concentration dependent Oxygen solubility and diffusivity in phosphoric acid

Fleige

Holst-Olesen

Wiberg³

et al. 2016

Electrochimica Acta

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Reactant diffusion and solubility is of utmost important for providing sufficient reactant concentrations at a catalytic active surface. In high temperature proton exchange membrane fuel cells (HT-PEMFCs) the electrolyte consists of concentrated phosphoric acid embedded into a polybenzimidazole (PBI) membrane. Despite the elevated operation temperature of 150°C, the observed oxygen reduction reaction (ORR) rates in HT-PEMFCs are significantly lower than in low temperature PEMFCs. Reduced reactant transport in combination with site blocking is often mentioned as possible inhibition factors. As a step towards studying the ORR under realistic conditions in half-cell setups, in the present study we investigate the oxygen solubility and diffusivity in diluted phosphoric acid electrolyte in a temperature range of 5 to 80 °C. The presented 2 work demonstrates and discusses under which conditions reliable data for these constants can be obtained. In particular it is shown that the product of oxygen solubility and diffusivity, which determines the oxygen mass transport, first increases as function of temperature, but then decreases again above 60 °C. It seems that the decrease in oxygen solubility at higher temperatures is correlated to an increase in the apparent ORR activation energy.

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“…Second, minimized phosphate anion adsorption on the catalyst particles prevented the blocking of the Pt active site [28]. Lastly, increased of O2 solubility in the acid mixture lowered the gas-transfer losses [30].…”

Section: Electrolyte Additives As Potential Methods To Reduce Phosphatmentioning

confidence: 99%

Efforts to Improve PBI/Acid Membrane System for High Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC)

et al. 2019

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The global expansion of industry and technology has brought various environmental issues especially in atmospheric pollution and global warming. These resulted in various R&D activities on renewable energy resources and devices. Developing high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) is one of them. Over the past decades, this research has been received the most attention for various stationary and transportation applications. This is due to inherent advantages of operation above 100 °C including improved tolerance toward CO poisoning, enhanced electrode kinetics, easier heat dissipation and water management as well as better thermodynamic quality of the produced heat. Poly (benzimidazoles)-phosphoric acid (PBI/PA) is the well-established membrane for HT-PEMFC applications replacing perfluorinated sulfonic acid (PFSA) membranes, which operate in the temperature range of below 100 °C. Nevertheless, there have been concerns on the durability and stability of such PEMFC, which negatively affected their widespread commercialization. In this paper, problems regarding this acid-base complex membrane system and modifications as well as some techniques used to overcome these issues will be outlined.

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Oxygen reduction on platinum in mixtures of phosphoric and trifluoromethane sulphonic acids

Cited by 14 publications

References 4 publications

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Evaluation of temperature and electrolyte concentration dependent Oxygen solubility and diffusivity in phosphoric acid

Efforts to Improve PBI/Acid Membrane System for High Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC)

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