Inclusion of surface heterogeneity in bridging PEM fuel cell electrode contamination kinetics and transport via a competitive Langmuir-Freundlich isotherm

Saiful Hasmady Abu Hassan, Kazuyoshi Fushinobu

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2 Citations (Scopus)

Abstract

This paper reports the development of mathematical model that bridges PEMFC transport phenomena with surface reaction kinetics in rough and heterogeneous electrodes, in which specifically the anode is modeled under carbon monoxide contamination. The mathematical bridging is done by converting surface concentration of reactants and contaminant into surface coverage of relevant adsorbates using the Langmuir-Freundlich isotherm to statistically include heterogeneity in binding site energetics. Thermodynamically optimized kinetic rate and equilibrium constants are calculated using coverage-dependent activation energies and provided as input to the HOR, ORR, and a kinetic-based limiting current model developed to solve for the distribution of activation overpotential. A novel model for a closed-form calculation of activation overpotential is proposed to allow numerical investigation via a galvanostatic approach. The kinetic reaction models are highly coupled with three-dimensional transport equations and solved iteratively under single-phase and steady-state conditions. Comparison is done with respect to two sets of available literature data in order to test the kinetic model validity under variation of CO concentrations and cell operating temperatures, in which good agreement is found. The results confirm that a Langmuir-Freundlich isotherm could be a more suitable isotherm compared to the extensively used Langmuir-specific isotherm for rough heterogeneous surfaces physically found in PEMFC catalysts. Results from the model show that rate of HOR is higher under the ribs of the cell since most of the active sites under channel are blocked with CO, with the effect exacerbated at lower temperatures.

Original languageEnglish
Pages (from-to)3387-3405
Number of pages19
JournalJournal of Solid State Electrochemistry
Volume18
Issue number12
DOIs
Publication statusPublished - 09 Dec 2014

Fingerprint

fuel cells
Isotherms
Fuel cells
isotherms
contamination
Contamination
inclusions
Carbon Monoxide
Electrodes
Kinetics
electrodes
kinetics
Proton exchange membrane fuel cells (PEMFC)
Reaction kinetics
reaction kinetics
Chemical activation
activation
Equilibrium constants
Surface reactions
Binding sites

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Electrochemistry
  • Electrical and Electronic Engineering

Cite this

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title = "Inclusion of surface heterogeneity in bridging PEM fuel cell electrode contamination kinetics and transport via a competitive Langmuir-Freundlich isotherm",
abstract = "This paper reports the development of mathematical model that bridges PEMFC transport phenomena with surface reaction kinetics in rough and heterogeneous electrodes, in which specifically the anode is modeled under carbon monoxide contamination. The mathematical bridging is done by converting surface concentration of reactants and contaminant into surface coverage of relevant adsorbates using the Langmuir-Freundlich isotherm to statistically include heterogeneity in binding site energetics. Thermodynamically optimized kinetic rate and equilibrium constants are calculated using coverage-dependent activation energies and provided as input to the HOR, ORR, and a kinetic-based limiting current model developed to solve for the distribution of activation overpotential. A novel model for a closed-form calculation of activation overpotential is proposed to allow numerical investigation via a galvanostatic approach. The kinetic reaction models are highly coupled with three-dimensional transport equations and solved iteratively under single-phase and steady-state conditions. Comparison is done with respect to two sets of available literature data in order to test the kinetic model validity under variation of CO concentrations and cell operating temperatures, in which good agreement is found. The results confirm that a Langmuir-Freundlich isotherm could be a more suitable isotherm compared to the extensively used Langmuir-specific isotherm for rough heterogeneous surfaces physically found in PEMFC catalysts. Results from the model show that rate of HOR is higher under the ribs of the cell since most of the active sites under channel are blocked with CO, with the effect exacerbated at lower temperatures.",
author = "{Abu Hassan}, {Saiful Hasmady} and Kazuyoshi Fushinobu",
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