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Heat and mass transport phenomena in the micro-pore structure of PEM fuel cell catalyst layer : 고분자 전해질 연료전지의 촉매층 미세 기공 구조에 따른 열 및 물질 전달 현상 연구

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Authors

손영준

Advisor
차석원
Major
기계항공공학부
Issue Date
2012-02
Publisher
서울대학교 대학원
Abstract
Water management is still an essential element for polymer electrolyte membrane (PEM) fuel cells. Specifically, oxygen diffusion in cathode catalyst layer (CCL) has been a main reaction rate determining factor at high current density region or concentration loss region. To investigate the effect of oxygen diffusion in CCL, microstructure controlled MEAs were fabricated as other electrochemical characterizations, for example, effective catalyst surface area or Pt/C contents are identical. The cell performance is higher for the large pore catalyst layer than for small pore in concentration loss region. To elucidate those experimental results, fuel cell 1D model implemented the exponential correlations between effective diffusion coefficient of oxygen and accumulated water film thickness in the simulated CCLs was suggested as a novel approach in this study.
Simulated catalyst layer microstructure consisted with agglomerate particles was generated to examine the experimental results for two MEA samples of which the porosity was 0.454 and 0.644. In addition, effective diffusion coefficients of oxygen were estimated by numerical simulation under water film accumulated situation. Exponential correlations were obtained between effective diffusion coefficient of oxygen and water film thickness in the simulated CCLs. Fuel cell 1D model implemented these correlations was developed. The simulated microstructure was evaluated by using virtual sphere packing method with mercury porosimetry measurement of the fabricated MEA samples.
The numerical solutions were validated with three different aspects of single cell experiments: the porosity of CCLs versus oxygen diffusivity according to the water film thickness in CCLs, stoichiometry versus concentration of oxygen dissolved into the water of agglomerate surface and relative humidity versus membrane proton conductivity and oxygen diffusivity. The simulation results show reasonably similar trend with experiments and analytical discussion was followed.
Language
eng
URI
https://hdl.handle.net/10371/156259

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