• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.131-135
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• 2011

It is, in general, believed that during the activation process, the proton conductivity increases due to wetting effect and the electrochemical resistance reduction, resulting in an increase in the fuel cell performance with time. However, until now, very scant information is available on the understanding of activation processes. In this study, dominant variables that effect on the performance increase of membrane electrode assemblies (MEAs) during the activation process were investigated. Wetting, pore restructuring and active metal utilization were analyzed systematically. Unexpectedly, the changes for both ohmic and reaction resistance characterized by the electrochemical impedance spectroscopy (EIS) after initial wetting process were much smaller when considering the degree of cell performance increases. However, the EIS spectra represents that the pore opening of electrode turns into gas transportable structure more easily. The increase in the performance with activation cycles was also investigated in a view of active metals. Though the particle size was grown, the number of effective active sites might be exposed more. The impurity removal and catalytic activity enhancement measured by cyclic voltammetry (CV) could be a strong evident. The results and analysis revealed that, not merely wetting of membrane but also restructuring of electrodeand catalytic activity increase are important factors for the fast and efficient activation of the polymer electrolyte fuel cells.

• Journal of the Korean Institute of Gas
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• v.4 no.1 s.9
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• pp.40-48
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• 2000

A fuel cell is an electrochemical device continuously converting the chemical energy in a fuel and an oxidant to electrical energy by going through an essentially invariant electrode-electrolyte system. Phosphoric acid fuel cell employs concentrated phosphoric acid as an electrolyte. The cell stack in the fuel cell, which is the most important part of the fuel cell system, is made up of anode where oxidation of the fuel occurs cathode where reduction of the oxidant occurs; and electrolyte, to separate the anode and cathode and to conduct the ions between them. Fuel cell performance is associated with many parameters such as operating and design parameters associated with the system configuration. In order to understand the design concepts of the phosphoric fuel cell and predict it's performance, we have here introduced the simulation of the fuel-cell stack which is core component and modeled in a 3-dimensional grid space. The concentration of reactants and products, and the temperature distributions according to the flow rates of an oxidant are computed by the help of a computational fluid dynamic code, i.e., FLUENT.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.846-853
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• 2005

For the performance prediction of a planar-type solid oxide fuel cell, the computational analysis of transport phenomena with a simplified treatment of heat generation by the electrochemical reaction is conducted. From the result of the computational analysis, it is shown that the electrochemical reaction is closely related to the transport phenomena inside a solid oxide fuel cell. Transport phenomena including heat and mass transfer influences on the distribution of local current density and, as a result, on the performance characteristics of the fuel cell. Computational analysis is also extended to the parametric study to investigate the performance behavior of the fuel cell with different amount of supplied fuel flow rates. It is also demonstrated that the mathematical formulation and computational procedures proposed in this study can be applied to prove the importance of the specific TPB area in the manufacturing process of electrodes in solid oxide fuel cells.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.648-654
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• 2005

The performance prediction of a planar-type solid oxide fuel ceil is conducted by a computational analysis. The transport processes are formulated with the help of a simplified treatment of heat generation by the electrochemical reaction. From the result of the computational analysis, it is shown that the electrochemical reaction is closely related to the transport phenomena inside a solid oxide fuel cell. Transport phenomena including heat and mass transfer have influence on the distribution of local current density and as a result, on the performance characteristics of the fuel cell. Computational analysis is also extended to the parametric study to investigate the performance behavior of the fuel cell with different amount of supplied fuel flow rates. It is also demonstrated that the mathematical formulation and computational procedures proposed in this study can be applied to prove the importance of the specific TPB(Three-Phase-Boundary) area in the manufacturing process of electrodes in a solid oxide fuel cell.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.350-355
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• 2015

To develop ceramic composite anodes of solid oxide fuel cells without metal catalysts, a small amount of barium carbonate was added to an $(La_{0.8}Sr_{0.2})(Cr_{0.5}Mn_{0.5})O_3(LSCM)$ - YSZ ceramic composite anode and its catalytic effects on the electrode performance were investigated. A barium precursor solution with citric acid was used to synthesize the barium carbonate during ignition, while a barium precursor solution without citric acid was used to create hydrated barium hydroxide. The addition of barium carbonate to the ceramic composite anode caused stable fuel cell performance at 1073 K; this performance was higher than that of a fuel cell with $CeO_2$ catalyst; however, the addition of hydrated barium hydroxide to the ceramic composite anode caused poor stability of the fuel cell performance.

• Journal of Hydrogen and New Energy
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• v.20 no.6
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• pp.499-504
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• 2009

The effect of gas diffusion layer (GDL) compression caused by different stack clamping pressures on fuel cell performance was experimentally studied in a miniature 5-cell proton exchange membrane fuel cell (PEMFC) stack. Three stacks with different GDL compressions, 15%, 35% and 50%, were prepared using SGL 10BC carbon fiber felt GDL and Gore 57 series MEA. The PEMFC stack performance and the stack stability were enhanced with increasing stack clamping pressure resulting in the best performance and stability for the stack with higher GDL compressions up to 50%. The excellent performance of the stack with high GDL compression was mainly due to the reduced contact resistance between GDL and bipolar plate in the stack, while reduced gas permeability of the excessively compressed GDL in the stack hardly affected the stack performance. The high stack clamping pressure also resulted in excessive GDL compression under the rib areas of bipolar plate and large GDL intrusion into the channels of the plate, which reduced the by-pass flow in the channels and increase gas pressure drop in the stack. It seems that these phenomena in the highly compressed stack enhance the water management in the stack and lead to the high stack stability.

• Journal of Hydrogen and New Energy
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• v.11 no.1
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• pp.19-27
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• 2000

The polymer electrolyte membrane fuel cell (PEMFC) system was developed. In order to enhance the performance of membrane electrode assembly (MEA), the transfer printing method of the electrocatalyst layer on membrane was developed. The $H_2/O_2$ single cell with an electrode area of $50cm^2$ was fabricated and tested using 20 wt.% Pt/C as an electrocatalyst and the commercial and hand-made MEA such as Nafion 115, Hanwha, Dow, Flemion T and Gore Select. The 100-cell PEMFC stack with an active electrode area of $300cm^2$ was designed and fabricated using 40 wt.% Pt/C and 30 wt.% Pt-Ru/C as a cathode and anode electrocatalysts, respectively. The performance of PEMFC system was obtained to be 7kW (250A at 28V) and 3.5kW (70A at 50V) at $80^{\circ}C$ by flowing $H_2/air$ and methanol reformed fuel gas/air, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.21-24
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• 2008

Proton Exchange Membrane Fuel Cell (PEMFC) is an attractive candidate for residential power generator due to fast start-up and stop, high efficiency, low emission, and high power density. In this study, we employ short module stack to understand the performance of the unit cell of the stack in terms of operating temperatures. To simulate the practical fuel cell stack of residential power generator, the structure and active area of the short module stack is kept the same as that of the practical fuel cell. The results shows that the electric potential of short module stack is different from the number of cells times the potential of unit cell because of cell-to-cell variation.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.374-380
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• 2015

In this paper, a dynamic model describing the 2 phase effect on the gas diffusion layer depending on load change of a fuel cell stack was developed to examine the effects of liquid water in fuel cell cathode gas diffusion layer on the fuel cell performance. For the developed model, 2 phase effect on the performance of a fuel cell stack depending on the load changes, concentration distribution of water vapor and oxygen inside a gas diffusion layer, the effect of the thickness and porosity of the gas diffusion layer on the fuel cell stack voltage were examined. As a result, a fuel cell stack voltage for the 2 phase model within the scope of the research become lower than that for the 1 phase model regardless of the load. Although oxygen molar concentration for the gas diffusion layer adjacent to the catalyst layer was the lowest, water vapor concentration is the highest. In addition, as thickness and porosity of the gas diffusion layer increased and decreased, respectively, the fuel cell stack voltage decreased.

• Journal of Hydrogen and New Energy
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• v.19 no.3
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• pp.232-238
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• 2008

Research has been proceeded on fuel cell which is fueled by hydrogen. Polymer electrolyte membrane fuel cell (PEMFC) is promising power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, temperature dependent performance. These problems could be solved by experiment which is useful for analysis and optimization of fuel cell performance and heat management. In this paper, when hydrogen flows constantly at the stoichiometry of ${\xi}=1.6$, the performance of the fuel cell stack was increased and the voltage difference between each cells was decreased according to the increase of air stoichiometry by 2.0, 2.5, 3.0. Therefore, the control of air flow rate in the same gas channel is important to get higher performance. Purpose of this research is to expect operation temperature, flow rate, performance and mass transportation through experiment and to help actual manufacture of PEM fuel cell stack.