Further development of an approximate model for mass transfer with reaction in porous gas-diffusion electrodes to include substrate effects

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

doi:10.1016/0013-4686(89)85017-0

Cited by 17 publications

(10 citation statements)

References 2 publications

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“…It also describes the physicochemical phenomena that occur in those layers: gas diffusion in gas-filled pores, gas dissolution, dissolved gas diffusion in liquid-filled pores, ohmic conduction, and electrochemical reaction. We used a variation of the standard flooded agglomerate model [20][21][22][23][24][25][26][27][28][29][30] that has successfully described the diffusion, adsorption, and reaction phenomena in cathode and anode electrodes of hydrogen phosphoric acid fuel cells (PAFC) and polymer electrolyte fuel cells (PEMFC). The agglomerate model describes the electrode's catalyst layer as a collection of homogeneously distributed spherical agglomerates that are composed of carbon particles on which the electrocatalyst platinum particles are dispersed.…”

Section: Mathematical Model Descriptionmentioning

confidence: 99%

Mathematical model for a direct propane phosphoric acid fuel cell

et al. 2005

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A mathematical model was developed and used to predict the performance of direct propane phosphoric acid (PPAFC) fuel cells, utilizing both Pt/C state-of the-art electrodes and older Pt black electrodes. It was found that the overpotential caused by surface processes on the platinum catalyst in the anode is much greater than the potential losses caused by either ohmic resistance or propane diffusion in gas-filled and liquid-filled pores. In one comparison, the anode overpotential (0.5 V) was larger than the cathode overpotential (0.3 V) at a current density of 0.4 A cm )2 for Pt loadings 4 mg Pt cm )2 . The need for sufficient water concentration at the anode, where water is a reactant, was indicated by the large effect of H 3 PO 4 concentration. In another comparison, the model predicted that at 0.2 A cm )2 , modern carbon supported Pt catalysts would produce 0.35 V compared to 0.1 V for unsupported Pt black catalysts that were used several decades ago, when the majority of the research on direct hydrocarbon fuel cells was performed. The propane anode and oxygen cathode catalyst layers were modeled as agglomerates of spherical catalyst particles having their interior spaces filled with liquid electrolyte and being surrounded by gasfilled pores. The Tafel equation was used to describe the electrochemical reactions. The model incorporated gas and liquid-phase diffusion equations for the reactants in the anode and cathode and ionic transport in the electrolyte. Experimental data were used for propane and oxygen diffusivities, and for their solubilities in the electrolyte. The accuracy of the predicted electrical potentials and polarization curves were normally within ±0.02 V of values reported in experimental investigations of temperature and electrolyte concentration. Polarization curves were predicted as a function of temperature, pressure, electrolyte concentration, and Pt loading. A performance of 0.45 V at 0.5 A cm )2 was predicted at some conditions.

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Section: Mathematical Model Descriptionmentioning

confidence: 99%

Mathematical model for a direct propane phosphoric acid fuel cell

et al. 2005

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“…Various models have been proposed to account for the behaviour of gas diffusion electrodes [1][2][3][4][5][6][8][9][10]]. An applicable model to explain the behaviour observed includes a porous backing acting as support, current collector and gas transport layer combined with a reaction layer consisting of a network of drowned and gas-filled pores.…”

Section: Theoretical Analysismentioning

confidence: 99%

“…To describe the behaviour of gas diffusion electrodes, many models have been proposed [1][2][3][4][5][6]. Some models include possible gas-phase transport limitations, whereas others neglect the influence of these gas-phase phenomena, since the diffusion coefficient of the reactant gas dissolved in the liquid phase is small compared to the diffusion coefficient of the reactant gas in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

Mass transport in a hydrogen gas diffusion electrode

Vermeijlen

Janssen

1993

J Appl Electrochem

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Experimental data are presented concerning the diffusion-limited current density for hydrogen oxidation in a gas diffusion electrode (GDE) under various conditions. These current densities were obtained using mixtures of hydrogen and inert gases. To elucidate the dependence of the overall mass transport coefficient on the gas phase diffusion coefficient and the liquid phase diffusion coefficient of the hydrogen, a simplified model was derived to describe the transport of hydrogen in a GDE based on literature models. The GDE consists of a hydrophobic and a hydrophilic layer, namely a porous backing and a reaction layer. The model involves gas diffusion through the porous backing of the GDE combined with gas diffusion, gas dissolution and reaction in the reaction layer of the electrode. It was found that the transport rate of hydrogen under the experimental circumstances is determined by hydrogen gas diffusion in the pores of the porous backing, as well as in the macropores of the reaction layer. Diffusion of dissolved hydrogen in the micropores of the reaction layer, through the liquid, is shown to be of little significance. geometric electrode surface area (m 2) concentration of reactive component at the inlet of the gas compartment (tool m -3) concentration of reactive component in and at the outlet of the gas compartment (mol m -3) concentration of sulphuric acid in the solution compartment (tool m -3) concentration of reactive component in a gas diffusion electrode (mol m -3) interdiffusion coefficient for gas i in gasj at a temperature T (m 2 s -1) diffusion coefficient for electroactive species in solution (m 2 s -1) electrode potential (V) equilibrium electrode potential (V) upper limit electrode potential (V) volumetric flow rate at the inlet of the gas compartment (m 3 s -1) volumetric flow rate of nitrogen at the inlet of the gas compartment (m -3 s -1) mass flow rate at the inlet of the gas compartment (kg s -l) Faraday constant (A s mo1-1) Henry's constant defined by Equation 9 (-) diffusion limited current density for gas diffusion electrode (A m -2) calculated diffusion limited current density for gas diffusion electrode (A m -2) local current density for hydrogen oxidation reaction in a micropore of the gas diffusion electrode (Am -2) current for hydrogen production (A) ©

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“…The primary distinguishing difference between this rigorous model and earlier modelling work (Giordano, et al, 1991;Savinell and Fritts, 1988;Yang, et al, 1989;Ridge, et al, 1989) was the inclusion of electro-osmotic and pressure-driven water transport associated with a polymer-electrolyte fuel cell. This model treated three distinct regions (see Figure 1): a membrane region of hydrated polymer electrolyte, an active catalyst layer formed by the overlap of the membrane and the gas diffusion electrode, and a region known as the gas diffuser.…”

Section: Simplified Model For Oxygen Transport With Simplified Model mentioning

confidence: 99%

Simplified Model for Oxygen Transport With Reaction in a Polymer-Electrolyte Fuel Cell

et al. 2008

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S olid-polymer-electrolyte fuel cells have received much attention recently because of dramatic improvements in the performance of single laboratory cells and the subsequent potential for application in both power generation and transportation. Mathematical models of the fuel cells that include several simultaneous transport processes would be useful in future design and scale up.Detailed one-dimensional models of solid-polymer-electrolyte fuel cells that include the transport of both water and dissolved hydrogen and oxygen across the cell are those of Verbrugge (1991, 1992), Springer et al. (1991), andEikerling et al. (1998). In the former, the membrane was assumed to be uniformly hydrated with the constant transport properties, while the latter two references focused on the effects of non-uniform membrane water content on mass transfer. Two-dimensional models are those of Newman (1993a, 1993b) and Yi and Nguyen (1998) who used concentrated solution theory and the work of Nguyen and White (1991) who adapted the results of Springer et al. (1991) to the membrane transport where these studies include heat and mass transfer in the fl ow channels. The latter work was extended to provide the computational framework for the design of fuel cell stacks (1997 Finite element analyses for multi-dimensional effects have been developed by Lee and Lalk (1998) to include thermal properties in fuel cell stacks and by Futerko and Hsing (2000) to include the effects of temperature and pressure on membrane water content and current density. All of the work above including limitations due to membrane and catalyst degradation by impurity ions is summarized by Okada (2001).The memory and computational requirements for the design of fuel cell systems can be great, particularly if the onedimensional model of mass transport across the cell require simultaneous solution of coupled ordinary differential equations. The purpose of the present paper is to illustrate an analytical procedure that would eliminate the latter requirement. A rigorous mathematical model for an ion-exchange membrane attached to a gas-fed porous diffusion electrode was published some time ago by Bernardi and Verbrugge (1991). In particular, the model was applied to simulate the oxygen electrode of a solid-polymer-electrolyte fuel cell, with emphasis on representing cell polarization characteristics, water transport and platinum A simplifi ed mathematical model for an ion-exchange membrane attached to a gas-fed porous electrode is developed to simulate the oxygen electrode of a solid-polymer-electrolyte fuel cell. In particular, the present model is derived from an earlier rigorous one of Bernardi and Verbrugge(1991) by neglecting the Peclet number for the transport of dissolved oxygen within the catalyst. The advantage of this simpler model is that it can be solved analytically, eliminating the need for numerical simulation. Longitudinal profi les for the dissolved oxygen concentration and catalyst current density calculated from the present model are in good agr...

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Further development of an approximate model for mass transfer with reaction in porous gas-diffusion electrodes to include substrate effects

Cited by 17 publications

References 2 publications

Mathematical model for a direct propane phosphoric acid fuel cell

Mathematical model for a direct propane phosphoric acid fuel cell

Mass transport in a hydrogen gas diffusion electrode

Simplified Model for Oxygen Transport With Reaction in a Polymer-Electrolyte Fuel Cell

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