• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.264-270
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• 2006

In this research, volume reduction of activated sludge using electrolysis was studied to find an optimum condition using lab scale experiments. Wasted sludge was treated by electrolysis with controlling current density, chloride concentration, electrode distance, and reaction time. Volume of return sludge was reduced by 9.79% in average while maximum was 16.7%. Sludge volume reduction efficiency was affected by current density and reaction time. It was reversely proportional to the electrode distance. Especially current density was effective on the system performance significantly. Electric conductivity, salinity and COD were increased by electrolysis implying sludge disintegrated and converted to COD in part. An empirical equation for total solid removal efficiency by electrolysis was proposed by multiple linear regression analysis as: $TS_{rem}$(%) = 5.534 ${\times}$ current density (A/l) + 0.178 ${\times}$ reaction time (m) + 2.758.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.357-365
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• 2008

Hydrogen energy becomes more attractive in that it can resolve the exhaustion of fossil fuels and their environmental problems. Until now, water electrolysis has been a interesting technique to produce hydrogen from non-fossil fuels. In principle, water electrolysis is an environmentally friendly technique to split water into hydrogen and oxygen, so that it can be utilized without any limitation of resources. Herein, we introduce basic understanding and three types of water electrolysis. Furthermore, the research trend and patent analysis will be followed along with an outlook.

• Journal of the Korean Electrochemical Society
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• v.26 no.2
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• pp.19-34
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• 2023

Due to the intermittency of renewable energy sources, a need to store and transport energy will increase. Hydrogen production through water electrolysis will provide an excellent way to supplement the intermittency of renewable energy sources. While alkaline water electrolysis is currently the most mature technology, it has drawbacks of low current density, large footprint, gas crossover, etc. The PEM water electrolysis has potential to replace the alkaline electrolysis. However, expensive catalyst material used in the PEM electrolysis has been the bottleneck of widespread use. In this review, we have reviewed recent efforts to reduce catalyst loading in PEM water electrolysis. In core-shell nanostructures, the precious metal catalyst forms a shell while heteroatoms form a core. In this way, the catalyst loading can be significantly reduced while maintaining the catalytic activity. In another approach, a corrosion-resistant support is utilized, which provides a stable platform to impregnate precious metal catalyst.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.667-673
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• 2009

This study has carried out to evaluate the performance of single (electrolysis, UV and ultrasonic process) and complex process (Electrolysis+UV, UV+Ultrasonic and Electrolysis+Ultrasonic) for the purpose of disinfection of Escherichia coli in water. The order of disinfection performance for E. coli in single process lie in: Electrolysis ${\fallingdotseq}$ UV >> ultrasonic process. OH radical was not produced in single disinfection process. Among the three kinds of complex process, disinfection performance of the Electrolysis+UV was higher than that of the other process (UV+Ultrasonic and Electrolysis+Ultrasonic). It demonstrated a synergetic effect between the UV and electrolysis. When the use of $Na_2SO_4$ as electrolyte instead of NaCl, current increase or more reaction time was needed for the complete disinfection. The disinfection performance of pre-electrolysis (20 W, 30sec) and post-UV (10 W, 30 sec) was higher than that of the simultaneous electrolysis+UV process at same electric power (30 W, 30 second).

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.567-575
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• 2023

Water electrolysis is undergoing active research as one of the promising technologies for producing effective green hydrogen. Using seawater directly as a raw material for a water electrolysis system can solve the problem of the limitations of existing freshwater raw materials, as seawater accounts for approximately 97% of the water on Earth. At the same time, abundant by-product materials can be obtained, representative examples of which are Cl₂, ClO^-, Br₂, and Mg(OH)₂ produced during electrolysis, depending on their composition and pH environment. In order to develop a successful seawater electrolysis system and oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts, it is necessary to understand the causes and consequences of reactions that occur in the seawater environment. Therefore, in this paper, we will investigate the reaction mechanism and characteristics of the seawater electrolysis system as well as the research and development trends of electrochemical catalysts used in anode and cathode electrodes.

• Journal of Adhesion and Interface
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• v.25 no.2
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• pp.50-55
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• 2024

Hydrogen is attracting much attention as a renewable energy source with high energy density and environmental friendliness. Among various hydrogen production methods, water electrolysis stands out as a clean hydrogen production technique that could lead the future of hydrogen production, as it does not emit carbon, and many studies are currently underway to realize this technology. However, the high overpotential, which increases the cost of hydrogen production, acts as a stumbling block, making the development of electrocatalysts extremely important. This paper aims to summarize and introduce recent research trends in the development of electrocatalysts for hydrogen evolution reaction and oxygen evolution reaction through interfacial engineering, and to deeply discuss the challenges in implementing next-generation water electrolysis devices.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.198-201
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• 2001

The mixed gas of Hydrogen and Oxygen is gained from water electrolysis reaction. It has constant volume ratio 2 : 1 Hydrogen and Oxygen, and it is used as a source of thermal energy by combustion reaction. This gas has better characteristics in the field of economy, efficiency of energy, and environmental intimacy than acetylene gas and LPG used for gas welding machine. So several studies of this gas are actively in progress nowadays. The object of this study is the optimization of power condition in the side of electrical for the high efficiency of water electrolysis equipment. First, chemical analysis of electrolysis is conducted, and the relation of electrical energy and chemical energy is quantitatively investigated. For basic experiment, unit electrode of singular electrolysis electrode is manufactured and experimented, results are compared and analyzed with simulation, and the electrolysis is electrically equivalent.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.575-580
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• 2023

An electrode was prepared by dip-coating NiFe₂O₄ powder on stainless steel (SUS) support for the application in the alkaline water electrolysis. The prepared electrode was analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), and was evaluated for the voltage properties with the change of current density in oxygen evolution reaction (OER) and hydrgen evolution reaction (HER) using 1, 3 and 7 M KOH solution. From the SEM and EDXS analysis, it was confirmed that the prepared electrode had NiFe₂O₄ on the SUS support. In OER and HER, the voltage in the 7 M KOH solution had a value of 1.35 and -1.90 V at 0.2 and -0.2 A/cm² of the current density, respectively. It was considered that the prepared electrode could be use as an electrode in the alkaline water electrolysis from the experimental results.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.241-245
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• 2016

Hydrogen is considered a potential future energy source. Among other applications of hydrogen, hydrogen-rich water is emerging as a new health care product in industrial areas. Water electrolysis is typically used to generate a hydrogen rich water system. We annealed 10AA carbon paper in air to use it as an electrode of a hydrogen rich water generator. Driven by annealing, structural changes of the carbon paper were identified by secondary electron microscope analysis. Depending on the various annealing temperatures, changes of the hydrophilic characteristics were demonstrated. The crystal structures of pristine and heat-treated carbon paper were characterized by X-ray diffraction. Improvement of the efficiency of the electrochemical oxygen evolution reaction was measured via linear voltammetry. The optimized annealing temperature of 10AA carbon paper showed the possibility of using this material as an effective hydrogen rich water generator.

• Journal of Electrochemical Science and Technology
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• v.7 no.1
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• pp.76-81
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• 2016

An anatase TiO₂ nanotube array (NTA) was fabricated by anodization and successive heat treatments. When the anatase TiO₂ NTA was cathodically polarized, its color changed to blue, and it could be used as an electrochemically active anode for an oxygen evolution reaction (OER) in alkaline water electrolysis. The structure of the blue anatase TiO₂ NTA was controlled by the anodization conditions and its catalytic activity increased with an increase of the surface area. The activity of the blue anatase TiO₂ NTA gradually reduced with the continued OER because of the partial oxidation of Ti³⁺ to Ti⁴⁺. However, an intermittent cathodic regeneration process could significantly slow its reduction rate. The blue anatase TiO₂ NTA could be an alternative anode for alkaline water electrolysis.