Direct methanol polymer electrolyte fuel cell modeling: reversible open-circuit voltage and species flux equations

Sandhu, Sarwan S.; Crowther, R. O.; Krishnan, Sarathkumar; Fellner, Joseph F.

doi:10.1016/s0013-4686(03)00218-4

Cited by 10 publications

(5 citation statements)

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“…1. It is noteworthy that the limiting current is not a linear function of methanol feed concentration and hence does not follow Fick's law over the entire range of methanol concentrations, as is assumed in many models of methanol transport [15,16,[23][24][25][26][27][28][29][30][31][32]. The observed curvature in measured data is attributed mainly to the effects of coupling of the fluxes.…”

Section: Resultsmentioning

confidence: 99%

“…Modelling is used to improve the understanding of the mass transport processes that occur and to gain insight in system optimisation with the materials presently used. The modelling work done so far mainly focuses on the transport processes as being of diffusive and convective character, following Fick's law with a correction for the electro osmotic drag [15,16,[24][25][26][27][28][29][30][31][32][33]. However, the findings imply that a strictly linear relation between feed concentration and crossover flow does not describe the transport properly; for example, the change in methanol swelling with methanol concentration [9,[17][18][19] together with the results obtained by Ren et al [14].…”

Section: Introductionmentioning

confidence: 99%

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A model for mass transport in the electrolyte membrane of a DMFC

Vernersson

Lindbergh

2007

J Appl Electrochem

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A steady state model for multicomponent mass transport was derived for the direct methanol fuel cell membrane. Data for development and validation of the model was taken both from experiments and literature. The experimental data was collected in a polarisation cell, where mass transport of methanol across the electrolyte membrane was measured through a potentiostatic method. The results from modelling and experiments showed good agreement. The model was capable of describing the non-linear response in mass transport to increased methanol feed concentration. The model also accurately described the change in membrane conductivity with methanol concentration. From the model transport equations, it was also possible to derive some characteristic transport parameters, namely the electro osmotic drag of both water and methanol, diffusive drag of water and methanol, and effective, concentration dependent, diffusion coefficients for methanol and water. Keywords Direct methanol fuel cell Á Modelling Á Mass transport Á Methanol crossover Á Electrolyte membrane List of symbols a i Activity of species ''i'' c i Concentration of species ''i'' [mol m -3 ] c T Sum of all concentrations [mol m -3 ] c 1 Concentration of water [mol m -3 ] c 2 Concentration of methanol [mol m -3 ] c 3 Concentration of protons [mol m -3 ] c 4 Concentration of sulphonic acid groups [mol m -3 ] D H 2 O Fickian diffusion coefficient of water [m 2 s -1 ] D CH 3 OH Fickian diffusion coefficient of methanol [m 2 s -1 ] D ij Stefan-Maxwell diffusion coefficient of species ''i'' and ''j'' [m 2 s -1 ] D 12 Stefan-Maxwell diffusion coefficient of water/methanol [m 2 s -1 ] D 13 Stefan-Maxwell diffusion coefficient of water/proton [m 2 s -1 ] D 14 Stefan-Maxwell diffusion coefficient of water/sulphonic acid [m 2 s -1 ] D 23 Stefan-Maxwell diffusion coefficient of methanol/proton [m 2 s -1 ] D 24 Stefan-Maxwell diffusion coefficient of methanol/sulphonic acid [m 2 s -1 ] D 34 Stefan-Maxwell diffusion coefficient of proton/sulphonic acid [m 2 s -1 ] f i Activity factor of species ''i'' [m 3 mol -1 ] F Faraday constant [As mol -1 ] i crossover Methanol crossover current [A m -2 ] i lim Limiting current of methanol crossover [A m -2 ] i load Current density load [A m -2 ] N i Flux of species ''i'' [mol m -1 s -1 ] N 1 Flux of water [mol m -1 s -1 ] N 2 Flux of methanol [mol m -1 s -1 ] N 3 Flux of protons [mol m -1 s -1 ] R Gas constant [J mol -1 K -1 ] T Temperature [K] z i Electric charge of species ''i'' T. Vernersson (

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A model for mass transport in the electrolyte membrane of a DMFC

Vernersson

Lindbergh

2007

J Appl Electrochem

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“…The methanol presence at the cathode decreases the available fuel cell voltage, also its oxidation at the cathode leads to lower fuel conversion efficiency in the form of lost fuel [48,49] [54]. The lower performance at lower and higher concentrations is due to concentration polarization and methanol crossover in both lower and higher concentrations respectively [55].…”

Section: Methanol Cross-over In Dmfcsmentioning

confidence: 99%

Electrochemical Investigation of Platinum Nanoparticles Supported on Carbon Nanotubes as Cathode Electrocatalysts for Direct Methanol Fuel Cell

Khotseng¹,

Ntlauzana²,

Ndungu³

et al. 2013

Advanced Chemistry Letters

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“…27, one can now examine the DMFC performance limit with state-of-the-art PtRu catalysts, assuming that the issues of methanol cross-over and cathode mass transport losses could be resolved by new membranes with low methanol permeability, novel methanol-tolerant cathode catalysts and cathode electrode structures with reduced flooding. This hypothetical, purely kinetically and ohmically limited performance at 80 • C, 150 kPa abs air, using a 25-µm Nafion 111 membrane (conductivity 0.14 S cm −1 [201]) and assuming an equilibrium potential of 1.165 V under these conditions [202], is shown in Fig. 28.…”

Section: Dmfc Performance Limit With Current Ptru Catalystsmentioning

confidence: 99%

Fuel Cells

Gasteiger

Garche

2008

Handbook of Heterogeneous Catalysis

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IntroductionFuel cells directly convert chemical energy into electrical energy, without the intermediate formation of heat and mechanical energy as in conventional energy conversion devices based on the Carnot cycle. The direct electrochemical energy conversions of H 2 at the anode and O 2 at the cathode occur spatially separated on two electrodes connected by electrolyte and, in principle, allow for higher energy conversion efficiencies as shown in Fig. 1. The largest efficiency differences between Carnotbased and fuel cell-based energy conversion are found in the low power range of <1 MW and especially <100 kW. These efficiency advantages minimize fuel consumption; furthermore, other environmental concerns are alleviated by fuel cells:• zero or ultra-low emission of pollutants and particulates • reduced noise emissions (some moving parts are part of the balance of plant).Despite these conceptual advantages of fuel cells and their long development history since Grove's discovery in 1893 [1], no real fuel cell markets exist as of today. The reason for this is their still high costs, caused mainly by the required materials and their relatively short lifetime in relation to competitive technologies. Their future market introduction is expected at first for portable applications, followed by stationary applications and finally for transportation applications. This expectation is based on the strong commitment of the car industry, the development of better and cheaper materials and the use of modeling methods to improve fuel cell and fuel cell system efficiencies.Among the different fuel cell types, the low-temperature proton exchange membrane fuel cell (PEMFC), the direct methanol fuel cell (DMFC), the high-temperature molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC) play the most important roles; historically, the phosphoric acid fuel cell (PAFC) and alkaline fuel cell (AFC) had significant importance. Caused by the low operating temperature of PEMFCs and DMFCs, electrocatalysis-related issues are more critical than in the case of high-temperature fuel cells. Therefore, although this chapter will give a general description of all fuel cell types, it will provide a more in-depth discussion of the anodic oxidation (i.e. for H 2 , CH 3 OH, etc.) * Corresponding author. and cathodic reduction (i.e. O 2 ) reactions occurring in PEMFCs and DMFCs; where appropriate, findings will be compared with the phosphoric acid fuel cell literature. Working Principles of Fuel CellsFuel cells are electrochemical power sources (ECPS), similar to primary and secondary batteries (also referred to as accumulators). Their working principle is shown schematically in Fig. 2. These electrochemical cells consist of two electrodes separated by an ionically conducting electrolyte. Conversion of chemical energy into electrical energy occurs at the interface between the electronically conducting electrodes and the ionically conducting electrolyte. In principal, the electrodes can operate in two modes, either transforming elec...

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Direct methanol polymer electrolyte fuel cell modeling: reversible open-circuit voltage and species flux equations

Cited by 10 publications

References 9 publications

A model for mass transport in the electrolyte membrane of a DMFC

A model for mass transport in the electrolyte membrane of a DMFC

Electrochemical Investigation of Platinum Nanoparticles Supported on Carbon Nanotubes as Cathode Electrocatalysts for Direct Methanol Fuel Cell

Fuel Cells

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