• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.107-109
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• 2006

This study focuses on a determination of amount of Pt in the Pt/C for catalysts of polymer electrolyte membrane fuel cells (PEMFC). PEMFC offer low weight and high power density and being considered for automotive and stationary power applications. The PEMFC performance is influenced by several factors, including catalysts and structure of electrode and membrane type. Catalyst of electrode is important factor for PEMFC. One of the obstacles prevent ing polymer electrolyte membrane fuel cells from commercialization is the high cost of noble metals to be used as catalyst, such as platinum To effectively use these metals, they have to be will dispersed to small particles on conductive carbon supports. The optimal amount of Pt in Pt/C for cathode catalyst was investigated by using polarization curves in single cell with $H_2/O_2$ operation.

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.52-58
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• 2013

In order to overcome the cost issue for commercialization of polymer electrolyte membrane fuel cell (PEMFC), this research was conducted for replacing platinum cathode catalyst with non-precious metal catalyst. The non-precious metal catalyst (Co-PANI-C) was synthesized by the simple reduction method with polyaniline (PANI), carbon black, and cobalt precursor without any heat treatment. Characterization of new Co-PANI-C composite catalysts was done by the measurement of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) for structure analysis and performed by rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) for electrochemical analysis. As a result, Co-PANI-C catalyst showed 60 mV lower on-set potential for oxygen reduction reaction (ORR) than Pt/C catalyst, but the overall reduction current of Co-PANI-C catalysts by ORR was still smaller than that of Pt/C. In addition, the ORR behavior of Co-PANI-C catalysts depending on the rotation speed of electrode and the stability of Co-PANI-C catalyst under potential cycling and the performance of fuel cell conditions are also discussed.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.35-43
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• 1998

Electrodes using for the anode electrode of direct methanol fuel cell with Pt/C and Pt/Ru/C catalyst were prepared and characterized by SEM, TEM, thermal analysis and electrochemical analysis. The half cell tests were carried out with 1 M $H_2SO_4$ electrolyte and 1 M $CH_3OH$ in order to evaluate the electrode performance. The employed electrochemical methods were cyclic vol-tammetry and potentiodynamic polarization experiments. It was found that 20 w% polytetrafluoroethylene (PTFE) content in catalyst showed the best performance due to the best platinum utilization on PTFE-containing catalyst layer. It was found that Pt/Ru/C binary catalyst inhibited the poisoning of anode electrode showing improved performance compared to the Pt/C catalyst by the adsorption of oxygen containing species on the electrode surface at same time. The apparent activation energy for methanol oxidation on the Pt/Ru/C and Pt/C catalyst layer was 11.60 kJ/mol and 26.85 kJ/mol, respectively.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.16-21
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• 2008

The key component of a direct methanol fuel cell (DMFC) is the membrane electrode assembly (MEA), which comprises a polymer electrolyte membrane and catalyst layers (anode and cathode electrode). Generally the catalyst layer is coated on the porous electrode supporter (e.g. carbon paper or cloth) using various coating methods such as brushing, decal transfer, spray coating and screen printing methods. However, these methods were disadvantageous in terms of the uniformity of catalyst layer thickness, catalyst loss, and coating time. In this work, we used bar-coating method which can prepare the catalyst layer with uniform thickness for MEA of DMFC. The surface and cross-section morphologies of the catalyst layers were observed by SEM. The performances and resistance of the MEAs were investigated through a single cell evaluation and impedance analyzer.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.95.2-95.2
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• 2011

In order to achieve high performance and low cost for commercial applications, the development of membrane electrode assemblies (MEA), in which the electrochemical reactions actually occur, must be optimized. Expensive platinum is currently used as an electrochemical catalyst due to its high activity. Although various platinum alloys and non-platinum catalysts are under development, their stabilities and catalytic activities, especially in terms of the oxygen reduction (ORR), render them currently unsuitable for practical use. Therefore, it is important to decrease platinum loading by optimizing the catalysts and electrode microstructure. In this study, we prepared several different MEAs (non-uniform Nafion$^{(R)}$ ionomer loading electrode) which have dual catalyst layers to find the optimal Nafion$^{(R)}$ ionomer distribution in the electrodes. We changed Nafion$^{(R)}$ ionomer content in the layers to find the ideal composition of the binder and Pt/C in the electrode. For MEAs with various ionomer contents in the anodes and cathodes, the electrochemical activity (activation overpotential) and the mass transport properties (concentration overpotential) were analyzed and correlated with the single cell performance. The dual catalyst layers MEA showed higher cell performance than uniformly fabricated MEA, especially at the high current density region.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.75.2-75.2
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• 2010

Polymer electrolyte fuel cells (PEFCs) have received a lot of attention as a power source for both stationary and mobile applications due to their attractive feature. In general, the performance of PEFCs is highly affected by the property of the electrodes. A PEFC electrode essentially consists of a gas diffusion layer and a catalyst layer. The gas difusion layer is highly porous and hydrophobicized with PTFE polymer. The catalyst layer usually contains electrocatalyst, proton conducting polymer, even PTFE as additive. Particularly, the proton conducting ionomer helps to increase the catalytic activity at three-phase boundary and catalyst utilization. Futhermore, it helps to retain moisture, resulting in preventing the electrodes from membrane dehydration. The most widely used proton conducting ionomer is perfluorinated sulfonic acid polymer, namely, Nafion from DuPont due to its high proton conductivity and good mechanical property. However, there are great demands for alternative ionomers based on non-fluorinated materials in terms of high temperature availability, environmental adaptability and production cost. In this study, the electrodes with the various content of the sulfonated poly(ether sulfone) ionomer in the catalyst layer were prepared. In addition, we evaluated electrochemical properties of the prepared electrodes containing the various amount of the ionomers by using the cyclic voltammetry and impedance spectroscopy to find an optimal ionomer composition in the catalyst layer.

• 한국전기화학회:학술대회논문집
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• 2003.07a
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• pp.83-88
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• 2003

PtRu alloy and $PtRu-WO_3$ nanocomposite thin-film electrodes for methanol electrooxidation were fabricated by means of a sputtering method. The structural and electrochemical properties of well-defined PtRu alloy thin-film electrodes were characterized using X-ray diffraction, Rutherford backscattering spectroscopy. X-ray photoelectron spectroscopy, and electrochemical measurements. The alloy thin-film electrodes were classified as follows: Pt-based and Ru-based alloy structure. Based on structural and electrochemical understanding of the PtRu alloy thin-film electrodes, the well-controlled physical and (electro)chemical properties of $PtRu-WO_3$, showed superior specific current to that of a nanosized PtRu alloy catalyst, The homogeneous dispersion of alloy catalyst and well-formed nanophase structure would lead to an excellent catalytic electrode reaction for high-performance fuel cells. In addition, the enhanced catalytic activity in nanocomposite electrode was found to be closely related to proton transfer in tungsten oxide using in-situ electrochemical transmittance measurement.

• Carbon letters
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• v.9 no.4
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• pp.303-307
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• 2008

The studies on integrated operation of fuel cell with fuel processor are very essential prior to its commercialization. In this study, Polymer Electrolyte Membrane Fuel Cell (PEMFC) was operated with a fuel processor, which is mainly composed of two parts, methanol steam reforming reaction and preferential oxidation (PROX). In fuel processor, ICI 33-5 (CuO 50%, ZnO 33%, $Al_2O_3$ 8%, BET surface area: $66\;m^2g^{-1}$) catalyst and CuO-$CeO_2$ catalyst were used for methanol steam reforming, preferential oxidation (PROX) respectively. PEMFC was operated by hydrogen fuel generated from fuel processor. The resulting gas from PROX reactor is used to operate PEMFC equipped with our prepared anode and cathode catalyst. PtRu/C catalyst gives more tolerance to CO.

• Clean Technology
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• v.13 no.4
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• pp.293-299
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• 2007

Direct coating of catalyst layer on the $Nafion^{(R)}$ membrane has been optimized in the process of fabrication of membrane electrode assembly (MEA) to enhance the performance of direct methanol fuel cell (DMFC). In this method, the contact resistance at the interface of the catalyst layer and the membrane was found to be low. The effect of catalyst loading, thickness of membrane and the gas diffusion layer (GDL) with or without the presence of micro-porous layer (MPL) on the performance of the MEA was also investigated. The MEA fabricated by the above-mentioned method exhibited a performance of $147\;mW/cm^2$ and $100\;mW/cm^2$ at $80^{\circ}C$ and $60^{\circ}C$, respectively, with the catalysts loading of $4\;mg/cm^2$.

• Advances in Energy Research
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• v.2 no.2
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• pp.73-84
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• 2014

Fuel cells of proton exchange membrane type (PEMFC) working with hydrogen in the anode and ambient air in the cathode ('air breathing') have been prepared and characterized. The cells have been studied with variable thickness of the cathode catalyst layer ($L_{CL}$), maintaining constant the platinum and ionomer loads. Polarization curves and electrochemical active area measurements have been carried out. The polarization curves are analyzed in terms of a model for a flooded passive air breathing cathode. The analysis shows that $L_{CL}$ affects to electrochemical kinetics and mass transport processes inside the electrode, as reflected by two parameters of the polarization curves: the Tafel slope and the internal resistance. The observed decrease in Tafel slope with decreasing $L_{CL}$ shows improvements in the oxygen reduction kinetics which we attribute to changes in the catalyst layer structure. A decrease in the internal resistance with $L_{CL}$ is attributed to lower protonic resistance of thinner catalyst layers, although the observed decrease is lower than expected probably because the electronic conduction starts to be hindered by more hydrophilic character and thicker ionomer film.