• Journal of the Korean Electrochemical Society
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• v.26 no.4
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• pp.56-63
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• 2023

The development of renewable energy technologies, such as solar, wave, and wind power, has led to the diversification of water electrolysis technologies, which can be easily coupled with renewable energy sources in terms of economics and scale. Water electrolysis technologies can be classified into three types based on operating temperature: low-temperature (<100 ℃), medium-temperature (300-700 ℃), and high-temperature (>700 ℃). It can also be classified by the type of electrolyte membrane used in the system. However, the concepts of thermodynamic and thermo-neutral voltages calculations and are very important factors in the evaluation of energy consumption and efficiency of water electrolysis technologies, are often confused. This review aims to contribute to a better understanding of the calculation of operating voltage and efficiency of PEM water electrolysis technologies and to clarify the differences between thermodynamic voltage and thermo-neutral voltage.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.251-258
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• 2016

This article reports current status of micro fuel cell-combined heat and power (${\mu}FC$-CHP) systems which utilize both power and heat generated by fuel cells. There are several options for constructing CHP systems and among them, fuel cells are the most useful and their total energy efficiency combining heat and power can reach up to about 90%. Fuel cells are classified as five types based on the electrolyte, but the most suitable fuel cell types for the ${\mu}FC$-CHP system are proton exchange membrane fuel cells (PEMFCs) and solid oxide fuel cells (SOFCs). ${\mu}FC$-CHP systems have several advantages such as decrease of the transmission-distribution loss, reduced costs of electricity due to distributed power generation, and environmental-friendliness owing to zero emission. The main drawback of the ${\mu}FC$-CHP systems is the high initial investment, however, it keeps decreasing as the technology development reduces production costs. Currently, Japan is the most leading country of the ${\mu}FC$-CHP market, however, Korea tries to expand the market by planning the deployment of 1 million units of ${\mu}FC$-CHP systems and governmental subsidiary supporting of half of the install price. In this report, integration technologies for connecting FC and CHP, and technology trends of leading countries are presented as well.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.4
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• pp.353-358
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• 2013

The current interruption method is considered to be an efficient way of measuring the resistance of a fuel cell. In this study, the ohmic area specific resistances (ASRs) of polymer electrolyte fuel cells with different types of bipolar plates were evaluated using the current interruption method. The ohmic ASRs of both a fuel cell with graphite bipolar plates and a fuel cell with graphite foil-based assembled bipolar plates decreased as the current density increased. On the other hand, with increasing cell temperature, the ohmic ASRs of a fuel cell with graphite bipolar plates were decreased by a reduction in the proton transport resistance through the membrane, and the ohmic ASRs of a fuel cell with graphite foil-based assembled bipolar plates were increased by the differences in thermal expansion between different components of the bipolar plates.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.498-504
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• 2008

Metal-reducing bacterium, Geobacter sulfurreducens is available for mediator-less microbial fuel cell (MFC) because it has biological nanowires(pili) which transfer electrons to outside the cell. In this study, in the anode chamber of the MFC system using G. sulfurreducens, the concentrations of NaCl, sodium phosphate and sodium bicarbonate as electrolytes were mainly optimized for the generation of electricity from acetate. 0.4%(w/v) NaClO and 0.5M $H_2SO_4$ could be utilized for the sterilization of acrylic plates and proton exchange membrane (major construction materials of the MFC reactor), respectively. When NaCl concentration in anode phosphate buffer increased from 5 to 50 mM, power density increased from 6 to $20\;mW/m^2$. However, with increasing sodium phosphate buffer concentration from 5 to 50 mM, power density significantly decreased from 18 to $1\;mW/m^2$. Twenty-four mM sodium bicarbonate did not affect electricity generation as well as pH under 50 mM phosphate buffer condition. Optimized anode chamber of MFC using G. sulfurreducens generated relatively high power density ($20\;mW/m^2$) with the maximum coulombic efficiency (41.3%).

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.579-584
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• 2011

Sulfonated poly (ether sulfone)s containing BFBN were prepared from 2,3-bis(4-fluorophenyl)-2-butenedinitrile , 4,4-sulfonyldiphenol and sulfonated 4,4'-difluorodiphenylsulfone sodium salt using potassium carbonate, and followed acidification reaction with 1M $H_2SO_4$. BFBN was prepared from 4-fluorobenzylcyanide, $CCl_4$, NaOH using trimethylbenzylammoniumchloride . Sulfonated poly(ether sulfone)s containing BFBN were studied by FT-IR, $^1H$-NMR spectroscopy, and thermo gravimetric analysis (TGA). The water uptake of synthesized S-PBFBN membranes exhibit 31~62% compared with 28% of Nafion 211. The S-PBFBN membranes exhibit proton conductivities ($80^{\circ}C$, RH 100) of 53.8~117.4 mS/cm compared with 137.4 mS/cm of Nafion 211.

• Membrane Journal
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• v.27 no.4
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• pp.344-349
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• 2017

Alkaline fuel cells using polymer electrolyte membranes are expected to replace proton exchange membrane fuel cells, which have similar system configurations. In particular, in alkaline fuel cells, a low-cost non-platinium catalyst can be used. In this study, to fabricate high performance and high durability anion exchange membranes for alkaline fuel cell systems, two kinds of supports, polybenzoxazole and polyethylene supports, were impregnated with Fumion FAA ionomer, by which we tried to fabricate the support-impregnated membrane which has higher mechanical strength and higher ion conductivity than the Fumion series. Finally, the Pore-filling membranes were successfully fabricated and ionic conductivity and mechanical properties were different depending on the properties of the supports. In the pore-filling membranes with Fumion ionomer on the PE support, excellent mechanical properties were obtained, but ionic conductivity decreased. On the other hand, when the PBO support was impregnated with Fumion ionomer, high ionic conductivity was shown after impregnation due to high basicity of PBO, but the mechanical strength was relatively low as compared with Fumion-PE membrane. As a result, it was concluded that it is necessary to consider the characteristics of the support according to the operating conditions of the alkaline fuel cell during the preparation of the pore-filling membranes.

• 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.62 no.1
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• pp.7-12
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• 2024

The durability of the catalyst support has a significant effect on the durability of proton exchange membrane fuel cells (PEMFC). The accelerated durability evaluation of the catalyst support is performed at a high voltage (1.0 to 1.5 V), and the catalyst and ionomer binder in the catalyst layer are also deteriorated, hindering the evaluation of the durability of the support. The existing protocol (DOE protocol) was improved to find conditions in which the support, which is a durability evaluation target, deteriorates further. A protocol (MDOE) was developed in which the relative humidity was lowered by 35% and the number of voltage changes was reduced. After repeating the 1.0 ↔ 1.5 V voltage change cycle, the catalyst mass activitiy (MA), electrochemical active area (ECSA), electrical double layer capacity (DLC), Pt dissolution and particle growth were analyzed. Reaching 40% reduction in mass activity, the MDOE protocol took only 500 cycles, reducing the number of voltage changes compared to the DOE method and increasing the degradation of the carbon support by 50% compared to the DOE protocol.