• Journal of the Korean Electrochemical Society
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• v.25 no.4
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• pp.154-161
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• 2022

The carbon-neutrality induced by the global warming is important for the modern society. Hydrogen has been received the attention as a new energy source to replace the fossil fuels. Polymer electrolyte membrane fuel cells, which convert the chemical reaction energy of hydrogen into electric power directly, are a type of eco-friendly power for future vehicles. Due to the sluggish oxygen reduction reaction and costly Pt catalyst in the cathode, the research related to the replacement of Pt-based catalysts has been vitally carried out. In this case, however, the performance is significantly different from each other and a variety of factors have existed. In this review paper, we rearrange and summarize relevant papers published within 5 years approximately. The selection of precursors, synthesis method, and co-catalyst are represented as a core factor, while the necessity of research for the further enhancement of activity may be raised. It can be anticipated to contribute to the replacement of precious metal catalysts in the various fields of study. The final objective of the future research is depicted in detail.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.224.2-224.2
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• 2010

연료개질기는 연료전지 시스템의 핵심 구성요소 중의 하나로 도시가스로부터 수소를 생산하는 역할을 담당한다. 연료개질기는 주로 탈황, 수증기 개질, 수성가스 전이, 선택적 산화 반응의 4단계로 구성되어 있으며 이 중 상온 탈황부분을 제외한 나머지 부분은 일체화 설계를 통해 제작된다. 탈황의 경우 도시가스에 포함된 부취제인 황화합물를 제거하여 후단에 위치한 촉매층이 황에 의해 피독되는 것을 막는 역할을 하며 주로 상온흡착식 탈황제를 사용한다. 황이 제거된 도시가스는 물과 함께 연료개질기로 도입되어 수증기 개질반응을 통하여 수소, 일산화탄소, 이산화탄소 및 소량의 메탄과 미반응 수증기로 구성된 개질가스로 전환된다. 이후의 수성가스 전이반응에서는 일산화탄소가 물과 반응하여 수소 생산량을 늘리며 동시에 일산화탄소의 농도를 낮추게 된다. 또한 고분자 전해질 연료전지에 공급되는 개질가스는 선택적 산화반응을 통하여 일산화탄소의 농도를 10ppm이하로 유지하게 된다. 이러한 기능의 연료개질기 개발의 주요 이슈로는 컴팩트화 및 고효율화이며 이 두가지 요소를 고려하여 연료개질기를 설계하여야 한다. 연료전지 시스템의 전체부피를 줄이기 위한 노력의 일환으로 연료개질기의 컴팩트화가 요구되는데 가정용 연료전지 기술 선진국인 일본 제품의 경우 $1Nm^3/h$급 연료개질기의 부피는 20L정도로 알려져 있다. 또한 연료전지 시스템의 효율은 연료개질기의 개질효율과 연료전지 스택의 발전효율의 곱으로 계산되기 때문에 연료개질기의 연료개질 효율은 전체 시스템의 효율에 직접적으로 영향을 미치게 된다. 한국에너지기술연구원에서는 수소생산량 기준 $1Nm^3/h$급 연료개질기의 개발을 완료하였으며 크기 및 효율면에서 선진국 제품과 비교하여 동등 또는 우위의 수준을 달성하였다. 연료개질기 내부의 혼합 및 분배 구조를 개선하고 각 촉매층의 최적 배치를 통해 연료개질기의 부피를 최소화 하였으며 연료개질기 내부에서 고온부위와 저온부위 사이의 최적 열교환을 통해 열효율을 극대화 시켰다. 현재 개발된 $1Nm^3/h$급 개질기의 단열 후 부피는 13.5L 그리고 단독운전 시 열효율은 80%(LHV)로 측정되었다. 또한 $1Nm^3/h$급의 연료개질기의 스케일-업 설계를 통하여 수소생산량 3, $5Nm^3/h$ 규모의 연료개질기를 개발하였으며 성능평가가 진행 중이다.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.58-64
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• 2001

YSZ ($8mol\%$ yttria-stabilized zirconia)-modified LSM $(La_{0.85}Sr_{0.15}MnO_3)$ composite cathodes were fabricated by formation of YSZ film on triple phase boundary (TPB) of LSM/YSZ/gas. The YSZ coating film greatly enlarged electrochemical reaction sites from the increase of additional TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 Um thickness) supported on an anode and then I-V characterization and AC impedance analyses were performed at temperature between $700^{\circ}C\;and\;800^{\circ}C$. As results of the impedance analysis on the cell at $800^{\circ}C$ with humidified hydrogen as the fuel and air as the oxidant, R1 around the frequency of 1000 Hz represents the anode Polarization. R2 around the frequency of 100Hz indicates the cathode polarization, and R3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The cell with the composite cathode produced power density of $0.55\;W/cm^2\;and\;1W/cm^2$ at air and oxygen atmosphere, respectively. The I-V curve could be divided into two parts showing distinctive behavior. At low current density region (part I) the performance decreased steeply and at high current density region (part II) the performance decreased gradually. At the part I the performance decrease was especially resulted from the large cathode polarization, while at the part H the performance decrease related to the electrolyte polarization.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.6-10
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• 2016

Until a recent day, degradation of PEMFC (Proton Exchange Membrane Fuel Cells) has been mainly studied in unit cell. But operation and degradation of real PEMFC going along in stack instead of unit cell. Therefore in this work, ADT (Accelerated Degradation Test) of PEMFC was done in stack and the result from stack's test was compared with that of unit cell. The polymer electrolyte membrane was degraded by repeated electrochemical and mechanical degradation method among several ADT methods. Current densities of MEA at 0.6V decreased in stack and unit cell, 28.4% and 27.8% respectively after ADT for 312 hours. Hydrogen crossover current densities of membrane increased in stack and unit cell, 16.8% and 15.2% respectively after ADT for 312 hours. The result of ADT in stack was similar that of ADT in unit cell, which showed that ADT method of unit cell was available to the stack.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.264-267
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• 2005

수소의 소규모 분산 생산 기술은 본격적 인 수소 인프라가 도입되기 전에 연료전지 자동차의 수소 충 전용이나 분산 발전형 연료전지의 수소 공급을 위해 필요하다. 생산 용량은 수소 기준으로 $10\~100 Nm^3/hr$ 정도로 현재로선 천연가스의 수증기 개질법이 가장 경제적인 공정으로 알려져 있다. 소규모 생산에 따른 열효율 저하를 줄이 기 위해 단위 공정들이 통합된 컴팩트 개질 시스템의 개발이 필요하다. 핵심 기술인 컴팩트 리포머의 국산화 기술 확보를 위하여 $20 Nm^3/hr$용량의 동심관형 리포머를 설계, 제작하였다. 내부구조는 제작의 단순화를 고려하여 중첩된 동심관이 배열되었고 압력 손실과 열웅력 발생을 억제하도록 유로를 배치하였다. 수증기개질 반응에 필요한 반응열은 리포머 본체에 부착된 버너를 이용하여 공급하였다. 성능 측정을 위한 부속 기기로 상온 흡착식 탈황기, 폐열 회수형 수증기 발생기, 반응물 예열을 위한 열교환기, 생성 가스 응축기를 설계 제작하여 전체 리포밍 시스템을 구성하였다. 반응 온도 $680\~720^{\circ}C$, 탄소 대 수중기 비(S/C ratio) $2.7\~3.2$ 조건에서 수증기 개질 반응을 수행하였다. 해당 반응 조건에서 메탄 전환율 $89\%$ 이상, 저위 발열량 기준 개질 열효율 $70\%$ 이상을 달성하였고 개질 생성가스 내 수소의 최대 유량은 $23.4Nm^3/h$였다. 개발된 리포밍 시스템은 고순도 수소 생산이 필요한 경우, 수소 수율 향상을 위한 고온 수성 가스 전화 반응기를 통합 가능하도록 열교환기 구성을 조정할 수 있으며 용융 탄산염 연료전지와 같이 고온형 연료전지의 경우 $550^{\circ}C$ 이상으로 개질 생성 가스를 공급하도록 구성할 수도 있다. 향후 리포머 본체의 개질 효율 향상 및 장치 소형화, 부속 기기의 최적화를 통한 전체 리포밍 시스템 개선, 스케일 업 설계를 위한 엔지니어링 설계 패키지 구성을 계획하고 있다.

• Membrane Journal
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• v.20 no.4
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• pp.267-277
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• 2010

Gas separation membranes have been developed for decades in various areas to replace the conventional processes. Membrane processes for gas separation have many advantages of energy saving, compact size, and easy scale-up. Nowadays, gas separation processes is widely spreaded in nitrogen generating system, hydrogen generating system, membrane dryer, on board inert gas generating system, natural gas purification, biogas purification and fuel cells. Carbon dioxide separation process using membrane would be a strong candidate of carbon dioxide capturing process. In order to broaden the scope of application of gas separation membranes, development of new materials which can overcome the borderline of Robeson's plot should be necessary, so that many researchers and companies are trying to develop the new materials like polymers containing cardo and spiro group and PIMs (polymers for intrinsic microporosity).

• Korean Chemical Engineering Research
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• v.51 no.5
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• pp.540-544
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• 2013

During start up and shut down of a proton exchange membrane fuel cells (PEMFC), the performance and lifetime of PEMFC were reduced. In this study, effect of startup and shutdown were investigated in dead-end type PEMFC using oxygen as a cathode gas with polarization curve, impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Dummy load which eliminates residual hydrogen and oxygen during startup and shutdown operation should be applied to mitigated the degradation of PEMFC performance. At 50% relative humidity (RH) under the repetitive on/off cycling, the cell performance decayed faster than at 100% RH because of corrosion of the cathode carbon support. Water suppling into cell reduced the degradation rate of dead-end type PEMFC during start up and shut down cycling at 50% RH.

• Resources Recycling
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• v.16 no.6
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• pp.28-33
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• 2007

Coal is the most abundant energy source and deposited in every area of world. Combustion process with lower efficiency has been mainly used. Therefore, implementation of more efficient technologies, involving gasification, combined cycles and fuel cells, would be a key issue in the plans for more efficient power generation. In these technologies, gasification has been studied for decades. However, coal gasification to high value combustible gas such as hydrogen and carbon monoxide is focused again due to high oil price. The gaseous product, called syngas, can be effectively utilized in a variety of ways ranging from electricity production to chemical industry (as feedstock). In this study, coal gasification with ultra high temperature steam has been performed. The effect of steam/carbon ratio on the produced gas concentrations, gasification rate and additional products like tar, ammonia and cyan compounds has been determined.

• Journal of the Korean Electrochemical Society
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• v.22 no.1
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• pp.1-12
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• 2019

The reduction of nitrogen to produce ammonia has been attracting much attention as a renewable energy technology. Ammonia is the basis for many fertilizers and is also considered an energy carrier that can power internal combustion engines, diesel engines, gas turbines, and fuel cells. Traditionally, ammonia has been produced through the Haber-Bosch process, in which atmospheric nitrogen combines with hydrogen at high temperature ($350-550^{\circ}C$) and high pressure (150-300 bar). This process consumes 1-2% of current global energy production and relies on fossil fuels as an energy source. Reducing the energy input required for this process will reduce $CO_2$ emissions and the corresponding environmental impact. For this reason, developing electrochemical ammonia-production methods under ambient temperature and pressure conditions should significantly reduce the energy input required to produce ammonia. In this review, we introduce the electrochemical nitrogen reduction reaction at ambient condition. Numerical studies on the electrochemical nitrogen reduction mechanism have been carried out through the computation of density function theory. Electrodes such as nanowires and porous electrodes have been also actively studied for further participation in electrochemical reactions.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.508-513
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• 2021

In order to improve the durability of a proton exchange membrane fuel cells (PEMFC), it is essential to improve the durability of the polymer membrane. In order to improve the durability of the membrane, an e-PTFE support and a radical scavenger are added. In this study, the chemical durability of the reinforced membrane with ePTFE support and the non-reinforced membrane was compared by Fenton reaction. In the Fenton experiment of the polymer membrane without the addition of a radical scavenger, the absorption rate of hydrogen peroxide solution and iron ions through the cross section of the specimen cut into small pieces was higher in the reinforced membrane, so that the fluorine outflow concentration was higher. According to the type and amount of radical scavenger added, the fluorine outflow concentration of the reinforced membrane has a large difference of more than 3 times, indicating that the effect of the radical scavenger was stronger than that of the support.