• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.23-32
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• 2020

The intermittent characteristics of renewable energy complicates the process of balancing supply with demand. Electrolysis technology can provide flexibility to grid management by converting electricity to hydrogen. Alkaline electrolysis has been recognized as established technology and utilized in industry for over 100 years. However, high overpotential of oxygen evolution reaction in alkaline water electrolysis reduces the overall efficiency and therefore requires the development of anode catalyst. In this study, Raney Ni-Zn-Fe electrode was prepared by electroplating and the electrode characteristics was studied by varying electroplating parameters like electrodeposition time, current density and substrate. The prepared Raney Ni-Zn-Fe electrode was electrochemically evaluated using linear sweep voltammetry. Physical and chemical analysis were conducted by scanning electron microscope, energy dispersive spectrometer, and X-ray diffraction. The plating time did not changed the morphology and composition of the electrode surface and showed a little effect on overpotential reduction. As the plating current density increased, Fe content on the surface increased and cauliflower-like structure appeared on the electrode surface. In particular, the overpotential of the electrode, which was prepared at the plating current density of 320 mA/㎠, has showed the lowest value of 268 mV at 50 mA/㎠. There was no distinguishable overpotential difference between the type of substrate for the electrodes prepared at 80 mA/㎠.

• 한국수소및신에너지학회논문집
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• 제7권1호
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• pp.29-37
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• 1996

Alkaline water electrolysis has been commercialized as the only large-scale method for a long time to produce hydrogen and the technology is superior to other methods such as photochemical, thermochemical water splitting, and thermal decomposition method in view of efficiency and related technical problem. However, such conventional electrolyzer do not have high electric efficiency and productivity to apply to large scale hydrogen production for energy or chemical feedstocks. Solid polymer electrolyte water electrolysis using a perfluorocation exchange membrane as an $H^+$ ion conductor is considered to be a promising method, because of capability for operating at high current densities and low cell voltages. So, this is a good technology for the storage of electricity generated by photovoltaic power plants, wind generators and other energy conversion systems. One of the most important R&D topics in electrolyser is how to minimize cell voltage and maximize current density in order to increase the productivity of the electrolyzer. A commercialized technology is the hot press method which the film type electrocatalyst is hot-pressed to soild polymer membrane in order to eliminate the contact resistance. Various technologies, electrocatalyst formed over Nafion membrane surface by means of nonelectrolytic plating process, porous sintered metal(titanium powder) or titanium mesh coated with electrocatalyst, have been studied for preparation of membrane-electrocatalyst composites. In this study some experiments have been conducted at a solid polymer electrolyte water electrolyzer, which consisted of single cell stack with an electrode area of $25cm^2$ in a unipolar arrangement using titanium mesh coated with electrocatalyst.

• 한국수소및신에너지학회논문집
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• 제18권4호
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• pp.391-398
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• 2007

The covalently cross-linked sulfonated polyetheretherketone (CL-SPEEK) membrane was prepared by four-step synthesis of sulfonation-sulfochlorination, partial reduction, lithiation, and cross-linking, and its electrochemical and mechanical properties were investigated for water electrolysis application. The prepared ion exchange membranes showed good electrochemical and mechanical properties; proton conductivity of 0.116 S/cm at $80^{\circ}C$, water uptake of 44.6%, ion exchange capacity of 1.75 meq/g-dry-memb., tensile strength of 64.25 MPa and elongation of 61.11%. The membrane electrode assembly (MEA) with homemade membranes were prepared by non-equilibrium impregnation-reduction (I-R) method. Especially, the electrochemical surface area (ESA) and roughness factor of CL-SPEEK electrolyte by cyclic voltammetry method were 23.46 $m^2/g$ and 307.3 $cm^2-Pt/cm^2$, respectively. The prepared MEA was used in the unit cell of water electrolysis and the cell voltage was 1.81 V at 1 A/$cm^2$ and $80^{\circ}C$, with platinum loadings of 1.31 mg/$cm^2$.

• Journal of Electrochemical Science and Technology
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• 제15권3호
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• pp.388-404
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• 2024

In the present work, the operating parameters were optimized using Box Behnken Design (BBD) in response surface methodology (RSM) to maximize the hydrogen production rate (R₁) and hydrogen production rate per unit watt consumed (R₂) of a proton exchange membrane electrolysis cell (PEMEC), a third response (R₃) which was the sum of the scaled values of R₁ and R₂ were selected to be maximized so that both hydrogen production rate and hydrogen production rate per unit watt consumed could be maximized. The major parameters which were influencing the experiment for enhancing the output responses were oxygen electrode/anode electrocatalyst loading (A), current supplied (B) and water inlet temperature (C). The commercial proton exchange membrane Nafion^® was used as the electrolyte. The acetylene black carbon (C_AB) supported IrO₂ was used as the electrocatalyst for preparing oxygen electrode/anode whereas commercial Pt (40 wt%)/C_HSA was used as the H₂ electrode/cathode electrocatalyst. The quadratic model was developed to predict the output/ responses and their proximity to the experimental output values. The developed model was found to be significant as the P values for both the responses were < 0.0001 and F values were greater than 1. The optimum condition for both the responses were O₂ electrode/anode electrocatalyst loading of 1.78 mg/cm², supplied current of 0.33 A and water inlet temperature of 54℃. The predicted values for hydrogen production rate (R₁) and hydrogen production rate per unit watt consumed (R₂) were 2.921 mL/min and 2.562 mL/(min·W), respectively obtained from the quadratic model. The error % between the predicted response values and experimental values were 1.47% and 3.08% for R₁ and R₂, respectively. This model predicted the optimum conditions reasonably in good agreement with the experimental conditions for the enhancement of the output responses of the developed PEM based electrolyser.

• 상하수도학회지
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• 제33권5호
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• pp.379-388
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• 2019

Chlorination and UV illumination are being widely applied to inactivate a number of pathogenic microbials in the environment. Here, we evaluated the inactivation efficiency of individual and combined treatments of chlorination and UV under various aqueous conditions. UV dosage was required higher in waste water than in phosphate buffer to achieve the similar disinfecting efficiency. Free chlorine generated by electrolysis of waste water was abundant enough to inactivate microbials. Based on these, hybrid system composed of sequential treatment of electrolysis-mediated chlorination and UV treatment was developed under waste water conditions. Compared to individual treatments, hybrid system inactivated bacteria (i.e., E. coli and S. typhimurium) and viruses (i.e., MS-2 bacteriophage, rotavirus, and norovirus) more efficiently. The hybrid system also mitigated the photo re-pair of UV-driven DNA damages of target bacteria. The combined results suggested the hybrid system would achieve high inactivation efficiency and safety on various pathogenic microbials in wastewater.

• Journal of Electrochemical Science and Technology
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• 제11권1호
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• pp.26-32
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• 2020

In this study, the side reactions that greatly affect the coulombic efficiency of a zinc-air secondary battery are quantitatively analyzed on the basis of the charging-discharging characteristics, open circuit self-discharge characteristics, and a series of calculations. In particular, the charge amounts consumed by water electrolysis and self-discharge during charging process are separately determined so that the charging efficiency (the amount of charge used in actual charging with respect to the applied charge amount) can be estimated, which would enable systematic understanding of the cause of coulombic efficiency degradation. Using two cells with different charging overvoltages, the validity of the proposed method can be assessed.

• 한국표면공학회지
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• 제17권1호
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• pp.1-6
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• 1984

The fluidized bed electrode reactor(FBER) with conducting particles has been made use of the removal of metals from dilute electroplating rinse water. The electrolysis was carried out under the conditions of diaphragm current density with 2~28A/$dm^2$ and bed expansion with 20~50%. Recirculating batch operations have been shown that the metal concentration dropped exponentially and may be taken down to 10 ppm. And then, the current efficiency at a concentration of 10 ppm copper was 37% under the conditions of 30% bed expansion and 6 A/$dm^2$, and at concentrated electrolyte (2000ppm copper) was over 80% in the range of 8~28A/$dm^2$ and 20~50% bed expansion. One of the technical possibilities of fluidized bed electrolysis is the separation of copper and nickel from a mixed solution of copper and nickel.

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.339-344
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• 2018

The gelling agent used in Zn-air cells plays a role in improving battery life. It prevents the evaporation of water and diffusion of $Zn^{2+}$ ions away from the current collector. Additional functionality was incorporated by replacing some of the gelling agents with new materials. Alcohols with moderate viscosity, namely maltose, sucrose, poly ethylene glycol 600, and 2-hydroxyethyl cellulose, were used to replace some gelling agents in this work. Among these alcohols, poly ethylene glycol 600 and 2-hydroxyethyl cellulose improved the cycle life of full cells. This improved cycle life was attributed to the inhibition of water electrolysis and the improved cycle life of the anode.

• 한국과학교육학회지
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• 제23권6호
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• pp.660-670
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• 2003

이 연구에서는 고등학교 학생들과 화학을 전공하는 예비 교사들, 그리고 화학교사들을 대상으로 전해질 수용액에서의 전기분해과정에 대한 이해의 정도를 설문과 면담을 통하여 알아보았다. 또한 이들에게 영향을 미치는 요인으로 고등학교 화학 II교과서의 서술 내용에 대한 분석도 같이 하였다. 연구 결과, 많은 교사들이 전기분해과정에서 산화반응과 환원반응과 전극에 대한 이해는 화학전지와 반대라고 단순히 암기하도록 설명하였다. 그러나 학생들의 이해 수준을 고려할 때, 그 원리를 명확하게 학생들에게 전달할 필요는 없다고 생각하였다. 또한 일부 교사들은 수용액의 전기분해에서 물의 전기 분해는 고려하지 못하는 오류도 발견하였다. 이들은 이미 이온화 된 입자들의 산화환원 반응에만 관심을 가지고 있었으며, 정작 전기분해를 통해 생성되는 물질에 대한 이해는 없는 것으로 나타났다. 이러한 경향은 고등학생들과 예비교사의 경우에도 유사하였다. 이러한 사고의 원인을 교과서의 서술 방식에서도 찾아볼 수 있었다.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.282-287
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• 2013

Hydrogen production from water using solar energy is attractive way to obtain clean energy resource. Among the various solar-to-hydrogen production techniques, a combination of a photovoltaic and an electrolytic cell is one of the most promising techniques in term of stability and efficiency. In this study, we show successful fabrication of precursor solution processed CIGS thin film solar cells which can generate high voltage. In addition, CIGS thin film solar cell modules producing over 2V of open circuit voltage were fabricated by connecting three single cells in series, which are applicable to water electrolysis. The operating current and voltage during water electrolysis was measured to be 4.23mA and 1.59V, respectively, and solar to hydrogen efficiency was estimated to be 3.9%.