Simulation and optimization of porous gas-diffusion electrodes used in hydrogen/oxygen phosphoric acid fuel cells—I. Application of cathode model simulation and optimization to PAFC cathode development

Yang, S.C.; Cutlip, Michael B.; Stonehart, P.

doi:10.1016/0013-4686(90)90083-c

“…Grens proposed the flooded porous electrode model [14,15]. Finally, the flooded agglomerate model from Giner [16] was extended by Cutlip to the socalled thin-film flooded agglomerate (TFFA) model [17] which was used in further study by Iczkowski, Björnbom, and Yang [18][19][20][21]. This model can be regarded as current state-of-the-art in fuel cell electrode modeling and was also used by Wang and Koda [6] in their study.…”

Section: List Of Symbolsmentioning

confidence: 98%

Thin-film flooded agglomerate model for silver-based oxygen depolarized cathodes

Pinnow

¹

,

Chavan

²

,

Turek

³

2011

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A mathematical model for a porous, silver-based electrode for the oxygen reduction in alkaline solutions, based on the thin film flooded agglomerate theory, was developed. These electrodes are employed in the energyefficient chlor-alkali electrolysis with oxygen depolarized cathodes. The model parameters were determined from overpotentials at different oxygen concentrations obtained in half-cell measurements. For the description of the reaction kinetics, it was necessary to introduce two Tafel equations, which might be explained by a change of the adsorption isotherm of the intermediate species during oxygen reduction. The model allows for a successful description of the overpotentials in the region of industrially relevant current densities. The analysis of the oxygen concentration distribution in the liquid electrolyte reveals that massive diffusion limitations occur although the calculated size of the agglomerates is only in the range of a few micrometers.Keywords Oxygen reduction Á Ag Á Chlor-alkali electrolysis Á Modeling List of symbolsA Constant describing the exchange current density (A m mol -1 ) c Molar concentration of oxygen dissolved in NaOH solution at boundary film-agglomerate (mol m -3 ) c* Molar concentration of oxygen dissolved in NaOH solution at boundary gas-film (mol m -3 ) c i Molar concentration of species i (mol m -3 ) D ij Binary Maxwell-Stefan diffusion coefficient for species i and j (m 2 s -1 ) D i,K Knudsen diffusion coefficient for species i (m 2 s -1 ) E°Equilibrium potential (V) E change Potential of change in Tafel slope (V) F Faraday constant (= 96485.3399(24) C mol -1 ) H Henry constant (Pa m 3 mol -1 ) j Current density (A m -2 ) k c (Chemical) reaction rate constant (s -1 ) L Characteristic length (m) m Molality of NaOH solution (mol kg -1 ) M i Molar mass of species i (kg mol -1 ) N iFlux of species i (mol m -2 s -1 ) P i Partial pressure of species i (Pa) P m Saturation partial pressure of water above NaOH solution (Pa) R Universal gas constant (= 8.314472(15) J mol -1 K -1 ) r Radius (m) r ag Radius of agglomerates (m) rReaction rate (mol m -3 s -1 ) S tf Specific surface area of thin film per total volume of reaction layer (m 2 m -3 )Length domain in reaction layer (m) z 0Length domain in gas diffusion layer (m) z 00Length domain in boundary layer (m)Greek letters d tf Thickness of thin film (m) DuPotential difference between solid electrode and electrolyte (V) e Porosity (dimensionless)

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“…Mathematical modeling of gas-fed DAFC polarization curves and their comparison with experimental polarization curves can provide valuable insights into the sources of performance loss in gas-fed DAFCs. Several one-dimensional (1-D), 2-D, and 3-D porous electrode models have been proposed and used in the field of fuel cells to model the performance of proton exchange membrane fuel cells (PEMFCs), − hydroxide exchange membrane fuel cells (HEMFCs), , and direct methanol fuel cells (DMFCs). − However, none of these models have yet been applied to DAFCs. Even though 2-D and 3-D porous electrode models are more realistic and complex, simplified and informative 1-D models are excellent starting points for understanding DAFCs.…”

mentioning

confidence: 99%

A High-Performance Gas-Fed Direct Ammonia Hydroxide Exchange Membrane Fuel Cell

Zhao

¹

,

Wang

²

,

Setzler

³

et al. 2021

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Recently, ammonia has become more attractive for carbon-neutral transportation. Both aqueous ammonia and gaseous ammonia can be utilized for direct ammonia hydroxide exchange membrane fuel cells (DAFCs). Using aqueous ammonia as feedstock for DAFCs presents significant drawbacks to practical stack operations, including higher ammonia crossover rate, increased probability of cathode flooding, and shunt currents. These drawbacks make gaseous ammonia the ideal feedstock for DAFCs. However, the main obstacle to adopting gas-fed DAFCs is their poor performance. Here, we demonstrate that anode humidity and operating temperature are two key factors impacting the performance of gas-fed DAFCs. For the first time, we also investigated the ammonia oxidation reaction (AOR) kinetics in liquid-base-free media at DAFC relevant temperatures and developed a kinetic model for the AOR under these DAFC applicable conditions. Finally, we constructed a one-dimensional (1-D) porous electrode model, simulated the polarization curves, and determined the sources of performance loss for gas-fed DAFCs.

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“…Furthermore, the concept of electrode activation by using small amounts of comparably expensive but stable coatings was introduced. Today, electrode activation has become common practice in the field of supported gas diffusion electrodes [102], e.g. for fuel cells.…”

Section: B Electrocatalysis Of Anodic Chlorine Evolution At Ruo 2 Anodesmentioning

confidence: 99%

Industrial Electrocatalysis

Kotrel

¹

,

Bräuninger

²

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction: From Industrial Electrochemistry to Electrocatalysis Catalysis in Organic Electrochemistry Synthesis of Adiponitrile The S imons Process Bleached Montan Wax—Regeneration of Chromic Acid Waste Water Treatment A Anodic Oxidation of Toxic compounds a Creating Reactive Oxygen Surface Species b Selective Conversion vs. Total Combustion c Common Electrode Materials B Cathodic Reduction of Toxic Compounds Catalysis in Inorganic Electrochemistry Chloralkali Electrolysis A Electrocatalytically Activated Dimensionally Stable Chlorine‐Evolving Electrodes ( DSAs ) B Electrocatalysis of Anodic Chlorine Evolution at Ru O 2 Anodes C Details of the Electrocatalytic Process D Preparation and Formulation of the Coatings for DSAs E Lifetime of Dimensionally Stable Chlorine‐Evolving Anodes F The Cathode Reaction—Oxygen‐Depolarized Cathode ( ODC ) Electrolysis of Hydrochloric Acid Preparation of Oxygen‐Depolarized Cathodes First Industrial HCl Electrolysis Using ODCs Oxygen‐Depolarized Cathodes for Chloralkali Electrolysis Industrial Water Electrolysis A The Electrochemistry of Water Electrolysis B Alkaline Water Electrolysis C PEM Water Electrolysis D High‐Temperature Water Electrolysis Summary and Outlook

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Simulation and optimization of porous gas-diffusion electrodes used in hydrogen/oxygen phosphoric acid fuel cells—I. Application of cathode model simulation and optimization to PAFC cathode development

Cited by 36 publications

References 7 publications

Thin-film flooded agglomerate model for silver-based oxygen depolarized cathodes

Thin-film flooded agglomerate model for silver-based oxygen depolarized cathodes

A High-Performance Gas-Fed Direct Ammonia Hydroxide Exchange Membrane Fuel Cell

Industrial Electrocatalysis

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