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Research Papers

Performance of a Direct Methanol Fuel Cell Operating Close to Room Temperature

[+] Author and Article Information
V. B. Oliveira

Departamento de Engenharia Química, Centro de Estudos de Fenómenos de Transporte, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

C. M. Rangel

Instituto Nacional de Energia e Geologia, Fuel Cells and Hydrogen Estrada do Paço do Lumiar, 1649-038 Lisboa, Portugal

A. M. F. R. Pinto1

Departamento de Engenharia Química, Centro de Estudos de Fenómenos de Transporte, Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugalapinto@fe.up.pt

1

Corresponding author.

J. Fuel Cell Sci. Technol 8(1), 011009 (Nov 03, 2010) (8 pages) doi:10.1115/1.4002311 History: Received July 10, 2009; Revised April 26, 2010; Published November 03, 2010; Online November 03, 2010

The direct methanol fuel cell (DMFC) is a promising power source for micro- and various portable electronic devices (mobile phones, PDAs, laptops, and multimedia equipment) with the advantages of easy fuel storage, no need for humidification, and simple design. However, a number of issues need to be resolved before DMFC commercialization, such as the methanol crossover and water crossover, which must be minimized in portable DMFCs. In the present work, a detailed experimental study on the performance of an “in-house” developed DMFC with 25cm2 of active membrane area, working near the ambient conditions is described. The influence on the DMFC performance of the methanol concentration in the fuel feed solution and of both anode and cathode flowrates was studied. Tailored membrane electrode assemblies (MEAs) were designed in order to select optimal working conditions. Different structures and combinations of gas diffusion layers (GDLs) were tested. Under the operating conditions studied it was shown that, as expected, the cell performance significantly increases with the introduction of gas diffusion layers and that carbon cloth is more efficient than carbon paper both for the anode and cathode GDLs. The results reported allow the setup of tailored MEAs enabling the cell operation at high methanol concentrations (high power densities) without sacrificing performance (i.e., achieving low methanol crossover values). The influence of the different parameters on the cell performance is explained under the light of the predictions from a previously developed one-dimensional model, coupling heat and mass transfer effects. The main gain of this work is to report DMFC detailed experimental data at near ambient temperature which are insufficient in literature. This operating condition is of special interest in portable applications.

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Figures

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Figure 1

Schematic diagram of the experimental set-up

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Figure 2

Photograph of the “in-house” designed DMFC

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Figure 3

Comparison of model predictions on (a) cell performance and (b) power density; dots: experimental data, lines: model predictions. Operating conditions: methanol concentration 0.75M and 2M, methanol flow rate 8 ml/min, and air flow rate 3.6 l/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 4

Influence of gas diffusion layers on (a) cell performance and (b) power density. Operating conditions: methanol concentration 0.75M and 2M, methanol flow rate 8 ml/min, and air flow rate 3.6 l/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 5

Effect of methanol concentration on (a) cell performance and (b) power density. Operating conditions: methanol flow rate 8 ml/min and air flow rate 3.6 l/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 6

Model prediction for the methanol crossover for different methanol feed concentrations. Operating conditions: methanol flow rate 8 ml/min and air flow rate 3.6 l/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 7

Influence of methanol flow rate on (a) cell performance and (b) power density. Operating conditions: methanol concentration 0.75M and air flow rate 3.6 l/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 8

Predicted methanol concentration profile in the anode catalyst layer (thickness 0.0023 cm) for different methanol flow rates. Operating conditions: methanol concentration 0.75M and air flow rate 3.6 l/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 9

Influence of air flow rate on (a) cell performance and (b) power density. Operating conditions: methanol concentration 0.75M and methanol flow rate 8 ml/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 10

Predicted oxygen concentration profile in the cathode diffusion layer (thickness 0.035 cm) for different air flow rates. Operating conditions: methanol concentration 0.75M and methanol flow rate 8 ml/min. Gas diffusion layers materials: carbon cloth at the anode and ELAT (E-TEK) at the cathode.

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Figure 11

Influence of the anode gas diffusion layer material on (a) cell performance and (b) power density. Operating conditions: methanol concentration 0.75M, methanol flow rate 8 ml/min, and air flow rate 3.6 l/min. Cathode diffusion layer material: ELAT (E-TEK).

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Figure 12

Predicted methanol concentration profile in anode flow channel layer (thickness 0.20 cm) for different anode gas diffusion layer material. Operating conditions: methanol concentration 0.75M, methanol flow rate 8 ml/min and air flow rate 3.6 l/min. Cathode diffusion layer material: ELAT (E-TEK).

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Figure 13

Influence of the cathode gas diffusion layer material on (a) cell performance and (b) power density. Operating conditions: methanol concentration 0.75M, methanol flow rate 8 ml/min, and air flow rate 3.6 l/min. Anode diffusion layer material: carbon cloth.

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Figure 14

Model predictions of the net water transport coefficient for different cathode gas diffusion layer material. Operating conditions: methanol concentration 0.75M, methanol flow rate 8 ml/min, and air flow rate 3.6 l/min. Anode diffusion layer material: carbon cloth.

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