• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.58-61
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• 2023

The activation process is essential for PEMFC to improve initial performance. The most commonly used activation method is a voltage change (load change) method, which may accompany degradation of the electrode catalyst if excessively performed. In many activation processes, the voltage change range is activated in a wide range from 0.4 V to OCV, and research is needed to reduce the voltage change range in order to prevent electrode catalyst degradation and shorten the activation time. Therefore, in this study, when the activation voltage range was 0.4~0.6 V, 0.4~0.8 V, and 0.4~OCV, we tried to research and develop an effective activation method by analyzing the performance and characteristics of the electrode and polymer membrane. The performance improvement was the lowest in the activation with a wide voltage range from 0.4 V to the highest OCV, and the performance decreased by 10% when activated for 56 cycles. The 0.4~0.6 V activation cycle showed the highest performance improvement up to 20% and the smallest decrease in performance due to overactivation, indicating that it is optimal method.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.697-700
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• 2008

The underpotential deposited Bi on Pt($Bi_{upd}/Pt$) anode for formic acid fuel cells (FAFCs) was developed using multi-layered preparation method for better electrocatalytic utilization of Pt. The electron probe microanalysis (EPMA) result indicated that $Bi_{upd}$ remains through the catalyst layer during stability test. In performance test, the multilayered $Bi_{upd}$ on Pt black showed superior performance by approximately 200 mV at current density of $150mA/cm^2$ compared with PtRu black anode catalyst. Based on preparation condition of $Bi_{upd}/Pt$ black, carbon supported $Bi_{upd}/Pt/C$ electrode was prepared and it showed enhanced performance and stability.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.42-46
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• 2008

Even though fuel cell have high efficiency when pure hydrogen from gas tank is used as a fuel source, it is more beneficial to generate hydrogen from city gas (mainly methane) in residential application such as domestic or office environments. Thus hydrogen is generated by reforming process using hydrocarbon. Unfortunately, the reforming process for hydrogen production is accompanied with unavoidable impurities. Impurities such as CO, $CO_2$, $H_2S$, $NH_3$, $CH_4$, and $CH_4$ in hydrogen could cause negative effects on fuel cell performance. Those effects are kinetic losses due to poisoning of the electrode catalysts, ohmic losses due to proton conductivity reduction including membrane and catalyst ionomer layers, and mass transport losses due to degrading catalyst layer structure and hydrophobic property. Hydrogen produced from reformer eventually contains around 73% of $H_2$, 20% or less of $CO_2$, 5.8% of less of $N_2$, or 2% less of $CH_4$, and 10ppm or less of CO. This study is aimed at investigating the effect of carbon dioxide on fuel cell performance. The performance of PEM fuel cell was investigated using current vs. potential experiment, long run(10 hr) test, and electrochemical impedance measurement when the concentrations of carbon dioxide were 10%, 20% and 30%. Also, the concentration of impurity supplied to the fuel cell was verified by gas chromatography(GC).

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.20-24
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• 2022

In the process of long-term use of PEMFC (Proton Exchange Membrane Fuel Cells), chemical degradation of membrane electrode assembly (MEA) occurs due to corrosion of stack elements and contamination of supply gas. In this study, we investigated whether chemically degraded MEA can be recovered by acid washing. The performance was measured and compared in a PEMFC cell after contamination with iron ions and washing with an aqueous sulfuric acid solution. The performance was reduced by about 25% by 0.5 ppm iron ion contamination, and 97.1% performance recovery was possible by washing of 0.15 M sulfuric acid. The membrane resistance was increased due to iron ion contamination of the polymer membrane, and the ionic conductivity was restored by washing the iron ions from the membrane while minimizing the loss of the electrode catalyst by washing with a low-concentration sulfuric acid aqueous solution. The possibility of solving the decrease in durability caused by chemical contamination of PEMFC MEA by the acid washing was confirmed.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.31-39
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• 2005

Direct methanol fuel cell (DMFC) is considered as a candidate for portable power sources, that could overcome the disadvantages of lithium battery. But in order to attain commercial viability the long term stability of the DMFC should be achieved. Understanding the long-term behavior of membrane-electrode assembly (MEA) is a prerequisite to this purpose and the optimization of the MEA is also needed. In this study we have investigated the changes in performance and electrochemical properties of the MEA during extended operation and the effects of heat treatment of MEA on the long-term performance. The MEAs have been treated in an autoclave with saturated water vapor at 120$^{\circ}C$, vacuum oven at 140$^{\circ}C$ and boiling in organic solvents. The autoclaved MEA was found to be have the best long term performance. The on-off operation mode also increased the performance probably due to effective removal of products from the electrodes. Physical and electrochemical analyses using a scanning electron microscope, impedance analyser and half-cell technique have been done to characterize the MEAs.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.223-234
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• 2010

In this review, the theory and applications of the complex capacitance analysis, which can be utilized in analyzing capacitor-like electrochemical systems, were summarized. Theoretically, it was suggested that the imaginary capacitance plots (Cim vs. log f) can provide a simple way to analyze electrochemical characteristics of capacitive systems, without complicated mathematical calculations. The usefulness of the complex capacitance analysis has been demonstrated by applying it to analyze EDLC characteristics of practical porous carbon electrodes, ionic conductivities inside small pores, and ionic resistances in the catalyst layers of polymer electrolyte membrane fuel cells.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.235-238
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• 2005

Sulfonated poly(ether sulfone) copolymers (PESs) were synthesized using hydroquinone 2-potassium sulfonate (HPS) with other monomers (bisphenol A and 4-fluorophenyl sulfone). PESs with different $mole\%$ of hydrophilic group were prepared by changing the mole ratio of HPS in the polymerization reaction. The chemical structure and the thermal stability of these polymers were characterized by using $^1H-NMR$, FT-IR and TGA techniques. The PES 60 membrane, which has $60 mole\%$ of HPS unit in the polymer backbone, has a proton conductivity of 0.091 S/cm and good insolubility in boiling water. The TGA showed that PES 60 was stable up to $272^{\circ}C$ with a char yield of about $29\%\;at\;900^{\circ}C\;under\;N_2$ atmosphere. To investigate the single cell performance, the catalyst coated PES 60 membrane was used and a single cell test was carried out using $H_2/O_2$ gases as fuel and oxidant at various temperatures. We observed that the cell performance was enhanced by increasing the cell temperature. A current density of $1400 mA/cm^2$ at 0.60 V was obtained at $70^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.471-480
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• 2017

A proton exchange membrane fuel cell (PEMFC) operated at $150^{\circ}C$ was evaluated by a controlling different amount of phosphoric acid (PA) to a membrane-electrode assembly (MEA) without humidification of the cells. The effects on MEA performance of the amount of PA in the cathode are investigated. The PA content in the cathodes was optimized for higher catalyst utilization. The highest value of the active electrochemical area is achieved with the optimum amount of PA in the cathode confirmed by in-situ cyclic voltammetry. The current density-voltage experiments (I-V curve) also shows a transient response of cell voltage affected by the amount of PA in the electrodes. Furthermore, this information was compared with the production variables such as hot pressing and vacuum drying to investigate those effect to the electrochemical performances.

• Journal of the Korean Electrochemical Society
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• v.10 no.4
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• pp.279-282
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• 2007

When reformer for fuel cell is used, CO in hydrogen gas leads to a seriously decreased membrane electrode assembly (MEA) performance by catalyst poisoning. The effect of CO on performance of modified MEA by sputtering method is studied in this paper. The experimental results show that sputtered Pt and Ru thin film improve a single cell performance of MEA and sputtered metal thin film has a CO tolerance. The air injection process on anode show improved CO tolerance test result. Moreover, Pt, Ru and PtRu thin film by sputtering had influence on the CO tolerance with air injection process.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.4
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• pp.378-385
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• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.