• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.36-42
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• 2005

This study examined the feasibility of producing sulfuric acid and ammonia water from ammonium sulfate solution using two-compartment electrodialysis with a bipolar membrane (EDBM). Electrodialysis experiments were carried out with 20 wt% ammonium sulfate at different current densities and sulfuric acid concentrations in a concentrate compartment. The current efficiency increased with the current density from 25 to $100\;mA/cm^2$. Nevertheless, the efficiency was relatively low compared with that of general desalting electrodialysis, owing to the diffusion of sulfuric acid from the concentrate compartment to the diluate. The diffusion rate through the anion exchange membrane increased with the sulfuric acid concentration in the concentrate compartment, which decreased the current efficiency. Conversely, the electrical resistance decreased with increasing current density owing to the Joulian heat generated during water dissociation in the transition region of the bipolar membrane under a high electric field. From the experimental results, we concluded that operating at a higher current density is effective from the perspective of current efficiency and electrical resistance when producing sulfuric acid and ammonia water from ammonium sulfate using a two-compartment EDBM process. Further studies on the effects of increasing the sulfuric acid concentration on current efficiency are required to apply the EDBM process practically.

• Journal of the Korean Institute of Gas
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• v.11 no.1 s.34
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• pp.51-54
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• 2007

78-cell proton exchange membrane fuel cell(PEMFC) stack with an effective electrode area of $295cm^{2}$ were investigated its operational characteristics and effects of CO poisoning. When power output, 5.4 kW, was released at current density of $325mA/cm^{2}$ for 6 hours, stablility of each cell was showed the small deviation of 2.3%. Carbon monoxide is a conventional contaminant in the fuel obtained from reforming processes with an important influence on the performance of the PEMFC. The studies of continuous injection of CO presented (5-20 ppm) with the time gave information about poisoning and recovery processes of the stack.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.81.1-81.1
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• 2011

High temperature proton exchange membrane fuel cell (HT-PEMFC) has been regarded as a promising clean energy sources. In this study, a quasi-three-dimensional dynamic model of HT-PEMFC has been developed and the local dynamic characteristics are investigated. The model has the geometrical simplification of 2+1D reduction (quasi-3D). The one-dimensional model consists of nine control volumes in cross-sectional direction to solve the energy conservation and the species conservation equations. Then, the one-dimensional model is discretized into 25 local sections along the gas flow direction to account for gas and thermal transport in channels. With this discretization, the local characteristics of HT-PEMFC such as species conservation, temperature, and current density can be captured. In order to study the basic characteristics of HT-PEMFC, it is important to investigate the local dynamic characteristics. Thus, the model is simulated at various operating conditions and the local dynamic characteristics related to them are observed. The model is useful to investigate the distribution of HT-PEMFC characteristics and the physical phenomena in HT-PEMFC.

• Journal of Digital Convergence
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• v.19 no.5
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• pp.279-284
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• 2021

In this study, the performance and distribution of fluid concentration, pressure, and current density of a proton exchange membrane fuel cell was investigated. In this paper, the two different types of flow field design were compared, singel channel and 5-channels. As a result, the 5-channels of flow field showed the better performance than that of single chanel. Especially, the single channel showed better performance in terms of mass transfer loss area.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.159-165
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• 2016

The hydrogen has been recognized as a clean, nonpolluting and unlimited energy source that can solve fossil fuel depletion and environmental pollution problems at the same time. Water electrolysis has been the most attractive technology in a way to produce hydrogen because it does not emit any pollutants compared to other method such as natural gas steam reforming and coal gasification etc. In order to improve efficiency and durability of the water electrolysis, comprehensive studies for highly active and stable electrocatalysts have been performed. The platinum group metal (PGM; Pt, Ru, Pd, Rh, etc.) electrocatalysts indicated a higher activity and stability compared with other transition metals in harsh condition such as acid solution. It is necessary to develop inexpensive non-noble metal catalysts such as transition metal oxides because the PGM catalysts is expensive materials with insufficient it's reserves. The optimization of operating parameter and the components is also important factor to develop an efficient water electrolysis cell. In this study, we optimized the operating parameter and components such as the type of AEM and density of gas diffusion layer (GDL) and the temperature/concentration of the electrolyte solution for the anion exchange membrane water electrolysis cell (AEMWEC) with the transition metal oxide alloy anode and cathode electrocatalysts. The maximum current density was $345.8mA/cm^2$ with parameter and component optimization.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.412-419
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• 2023

Anion exchange membrane electrolysis is considered a promising next-generation hydrogen production technology that can produce low-cost, clean hydrogen. However, anion exchange membrane electrolysis technology is in its early stages of development and requires intensive research on electrodes, which are a key component of the catalyst-system interface. In this study, we optimized the pressure conditions of the hot-pressing process to manufacture cobalt oxide electrodes for the development of a high uniformity and high adhesion electrode production process for the oxygen evolution reaction. As the pressure increased, the reduction of pores within the electrode and increased densification of catalytic particles led to the formation of a uniform electrode surface. The cobalt oxide electrode optimized for pressure conditions exhibited improved catalytic activity and durability. The optimized electrode was used as the anode in an AEMWE single cell, exhibiting a current density of 1.53 A cm^-2 at a cell voltage of 1.85 V. In a durability test conducted for 100 h at a constant current density of 500 mA cm^-2, it demonstrated excellent durability with a low degradation rate of 15.9 mV kh^-1, maintaining 99% of its initial performance.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.99-107
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• 2002

Recently all kinds of structural materials are subjected to the severe corrosive environment. Especially corrosion problems of heat exchanger such as galvanic corrosion, erosion and cavitation raised by both contaminated solution and high velocity of fluid to increase cooling effect of heat exchanger have been frequently reported in these days. In this study two kinds of sheet materials and five kinds of tube materials are used for galvanic corrosion characteristics and their corrosion current density calculation. The tube materials having the most galvanic corrosion resistance between tube and sheet of heat exchanger were Al Brass(68700) and Al Brass(C6872TS) and although Ti tube predominantly indicated the highest individual corrosion resistance among those five tube materials. it appeared that Ti tube can be allowed as sheet materials to get galvanic corrosion easily. However it is considered that Cu-Ni tube materials is not only easy to produce galvanic corrosion significantly between tube and sheet regardless of kinds of sheet materials but also is appeared considerably its own high corrosion current density

• Korean Membrane Journal
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• v.10 no.1
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• pp.46-52
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• 2008

Optimization of ionomer solution was conducted in order to improve the performance of MEAs in PEMPC. The interface between membrane and electrodes in MEAs is crucial region determining fuel cell performance as well as ORR reaction at cathode. Through the modification of Nafion ionomer content at the interface between membrane and electrodes, an optimal content was obtained with Nafion 115 membranes. Two times higher current density was obtained with the outer Nafion sprayed MEA compared with the non-sprayed one. In addition, the symmetrical impedance spectroscopy mode (SM) exhibited that the resistances of membrane area, proton hydration, and charge transfer decreased as the outer Nafion is sprayed. From the polarization curves and SM, the highest current density and the lowest resistance was obtained at the outer ionomer content of $0.15\;mg\;cm^{-2}$.

• Clean Technology
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• v.10 no.1
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• pp.9-17
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• 2004

Direct methanol fuel cell(DMFC) with proton exchange membrane (PEM) has advantages over the conventional power source (e.g. vehicle). DMFC, however, has a problem to be solved such as methanol crossover, high anodic overpotential and limiting current density, etc. The physicochemical phenomena in DMFC can be described by coupled PDEs (partial differential equations), which can be solved by a PDE solver. In this paper, we utilized a commercial software FEMLAB to solve the PDEs. The FEMLAB is one of the software programs available which are developed as a solver for building physics problems based on PDEs and is designed to simulate systems of coupled PDEs which may be 1D, 2D, 3D, non-liner and time dependent. We performed simulation using the Tafel equation as an electrochemical reaction model to analyze methanol concentration profile in DMFC system. We confirm that the rapid decrease of methanol concentration at anodic catalyst layer with the increase of the current density is a main reason of the low performance in DMFC through simulation results.

• Membrane Journal
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• v.31 no.4
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• pp.262-267
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• 2021

The electrochemical performance of all vanadium redox flow battery (VRFB) using an electrolyte prepared from ammonium metavanadate and a cation exchange membrane (Nafion117) was evaluated. The electrochemical performance of VRFB was measured at a current density of 60 mA/cm². The average current efficiency of VRFB using the electrolyte prepared from ammonium metavanadate was 94.9%, the average voltage efficiency was 82.2%, and the average energy efficiency was 78.0%. In addition, it was confirmed that the efficiencies of VRFB using the electrolyte prepared from ammonium metavanadate had almost the same value as the efficiencies of VRFB using the electrolyte prepared with vanadyl sulfate (VOSO₄).