Oxide-Carbon Nanofibrous Composite Support for a Highly Active and Stable Polymer Electrolyte Membrane Fuel-Cell Catalyst

Jeon, Yukwon,Ji, Yunseong,Cho, Yong Il,Lee, Chanmin,Park, Dae-Hwan,Shul, Yong-Gun American Chemical Society 2018 ACS NANO Vol.12 No.7

<P>Well-designed electronic configurations and structural properties of electrocatalyst alter the activity, stability, and mass transport for enhanced catalytic reactions. We introduce a nanofibrous oxide-carbon composite by an in situ method of carbon nanofiber (CNF) growth by highly dispersed Ni nanoparticles that are exsoluted from a NiTiO<SUB>3</SUB> surface. The nanofibrous feature has a 3D web structure with improved mass-transfer properties at the electrode. In addition, the design of the CNF/TiO<SUB>2</SUB> support allows for complex properties for excellent stability and activity from the TiO<SUB>2</SUB> oxide support and high electric conductivity through the connected CNF, respectively. Developed CNF/TiO<SUB>2</SUB>-Pt nanofibrous catalyst displays exemplary oxygen-reduction reaction (ORR) activity with significant improvement of the electrochemical surface area. Moreover, exceptional resistance to carbon corrosion and Pt dissolution is proven by durability-test protocols based on the Department of Energy. These results are well-reflected to the single-cell tests with even-better performance at the kinetic zone compared to the commercial Pt/C under different operation conditions. CNF/TiO<SUB>2</SUB>-Pt displays an enhanced active state due to the strong synergetic interactions, which decrease the Pt d-band vacancy by electron transfer from the oxide-carbon support. A distinct reaction mechanism is also proposed and eventually demonstrates a promising example of an ORR electrocatalyst design.</P> [FIG OMISSION]</BR>

Eco-friendly Ammonia Oxidation on a Bimetal-based Catalyst Based on the Combined Effect of Ni and Cu for Hydrogen Production

Chanmin Jo(조찬민),Minseo Jeon(전민서),Dongin Choi(최동인),Uk Sim(심욱) 한국태양에너지학회 2024 한국태양에너지학회 학술대회논문집 Vol.2024 No.4

Efficient methane reforming at proper reaction environment for the highly active and stable fibrous perovskite catalyst

Jeon, Yukwon,Kim, Heeseon,Lee, Chanmin,Lee, Sunghun,Song, Soonho,Shul, Yong-gun Elsevier 2017 Fuel Vol.207 No.-

<P><B>Abstract</B></P> <P>The purpose of this work is to investigate proper hydrogen production methods from methane through the parametric study for the highly active and stable nanofibrous perovskite catalyst. A ruthenium doped lanthanide chromate (LaCr<SUB>0.8</SUB>Ru<SUB>0.2</SUB>O<SUB>3</SUB>) micro-fibrous perovskite catalyst is prepared and fixed to focus on the effect of reaction environments such as steam, partial oxidation and autothermal conditions. Temperatures, H<SUB>2</SUB>O/C and O<SUB>2</SUB>/C ratios were occasionally changed for the investigation of the effects and the optimization conditions. At the same perovskite catalyst system, the reaction at the autothermal atmosphere is the most effective conditions in terms of both CH<SUB>4</SUB> conversion and H<SUB>2</SUB> production, which was comparable to the theoretical calculations. It is found that conversion increases with oxygen at even low temperature while the H<SUB>2</SUB> productivity increases with much stable behavior at steam condition. These are more obvious at the elevated temperature with each optimized H<SUB>2</SUB>O and O<SUB>2</SUB> amounts for high activity by low activation energy. Time-on-stream runs conducted on these three reactions with each optimized conditions of 50h at 800°C, H<SUB>2</SUB>O/C=3 and O<SUB>2</SUB>/C=0.5. The perovskite micro-fiber catalyst at autothermal condition shows excellent CH<SUB>4</SUB> conversion of over 95%, H<SUB>2</SUB> production of around 70%, and even H<SUB>2</SUB>/CO of over 4. On the other hand, the reactivity at the steam condition is lower and even slow. The durability at the partial oxidation condition starts to decrease after 10h due to the instability of the perovskite at the extremely oxidative concentration which causes a relatively high coke formation. Therefore, it is worthwhile in suggesting proper autothermal reaction conditions for the highly active and stable perovskite catalyst like LaCr<SUB>0.8</SUB>Ru<SUB>0.2</SUB>O<SUB>3</SUB> micro-fibers.</P> <P><B>Graphical abstract</B></P> <P>The perovskite microfiber catalysts were introduced for the application to the methane reforming at reaction environments such as steam, partial oxidation and autothermal conditions. The purpose of this work is to investigate proper hydrogen production methods from methane through the parametric study for the highly active and stable nanofibrous perovskite catalyst.</P> <P>[DISPLAY OMISSION]</P>

Ag-loaded cerium-zirconium solid solution oxide nano-fibrous webs and their catalytic activity for soot and CO oxidation

Lee, Chanmin,Jeon, Yukwon,Kim, Taehyen,Tou, Akihiro,Park, Joo-Il,Einaga, Hisahiro,Shul, Yong-Gun Elsevier 2018 Fuel Vol.212 No.-

<P><B>Abstract</B></P> <P>The catalytic combustion of soot and CO is one of the key technologies required to meet rigorous emission standards. Recently, solid solution materials have been employed in heterogeneous catalysts because of their remarkable intrinsic activities and good stabilities. However, the low number of contact points between soot particles and the catalyst remains a challenge to enhancing catalytic performance. Thus, we herein report the preparation of Ce-ZrO<SUB>2</SUB> solid solution nano-fibrous web catalysts with a hierarchical structure using an electrospinning method, where Ag particles were loaded onto the surface of the Ce-ZrO<SUB>2</SUB> webs. X-ray diffraction, scanning transmission electron microscopy, and energy dispersive spectroscopic studies allowed us to investigate the morphological and crystal structures of the prepared Ce-ZrO<SUB>2</SUB> and Ag/Ce-ZrO<SUB>2</SUB> web catalysts. Moreover, the relationship between the Ce/Zr ratio and activated oxygen is discussed based on X-ray photoelectron spectroscopy results. Following the catalytic oxidation of soot and CO using our novel materials, we found that the Ce<SUB>0.67</SUB>Zr<SUB>0.33</SUB>O<SUB>2</SUB> web exhibited higher catalytic activities than the Ce<SUB>0.5</SUB>Zr<SUB>0.5</SUB>O<SUB>2</SUB> and Ce<SUB>0.33</SUB>Zr<SUB>0.67</SUB>O<SUB>2</SUB> webs, respectively. In addition, Ag/Ce<SUB>0.67</SUB>Zr<SUB>0.33</SUB>O<SUB>2</SUB> exhibited enhanced catalytic activity compared with the pristine Ce<SUB>0.67</SUB>Zr<SUB>0.33</SUB>O<SUB>2</SUB> for the oxidation of both soot (e.g., 500°C vs. 544°C at 50% conversion) and CO (e.g., 282°C vs. 408°C at 50% conversion). It therefore appeared that our proposed Ce-ZrO<SUB>2</SUB> solid solution nano-fibrous web catalysts bearing Ag particles exhibited superior redox properties and enhanced surface areas, and as such, are promising candidates for use in the oxidation of both soot and CO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ce-ZrO<SUB>2</SUB> solid-solution oxide fibrous webs were synthesized by electrospinning. </LI> <LI> Ag particles were deposited to improve catalytic activity. </LI> <LI> Ag/Ce<SUB>0.67</SUB>Zr<SUB>0.33</SUB>O<SUB>2</SUB> exhibited superior catalytic activity to other sample. </LI> <LI> Redox property of Ag and enhanced surface areas improved the catalytic oxidation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Phosphate-Modified TiO₂/ZrO₂ Nanofibrous Web Composite Membrane for Enhanced Performance and Durability of High-Temperature Proton Exchange Membrane Fuel Cells

Lee, Chanmin,Park, Jeongho,Jeon, Yukwon,Park, Joo-Il,Einaga, Hisahiro,Truong, Yen B.,Kyratzis, Illias L.,Mochida, Isao,Choi, Jonghyun,Shul, Yong-Gun American Chemical Society 2017 Energy & fuels Vol.31 No.7

<P>An Aquivion/titanium zirconium oxide nanofibrous web composite membrane was prepared and tested as a proton exchange membrane in a hydrogen/air fuel cell. The incorporation of a small dose (9 wt % membrane) of a uniformly distributed electrospun titanium zirconium oxide (TiO2/ZrO2; Ti/Zr = 1:1 atomic ratio) nanofibrous web significantly improved hydromechanical stability of the composite membranes, which exhibited approximately 2 times higher water retention and 30 times lower dimensional change than a pristine Aquivion membrane under in-water membrane hydration conditions. Phosphate functionalities were successfully added onto the nanofiber surface, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The added phosphate functionality resulted in higher proton conductivity of the prepared composite membrane compared to the non-modified TiO2/ZrO2 nanofibrous web composite membrane [e.g., 0.027 S cm(-1) versus 0.021 S cm(-1) at 120 degrees C and 40% relative humidity (RH)]. A single cell test also showed the effect of an added TiO2/ZrO2 nanofibrous web. A single cell with an Aquivion/TiO2/ZrO2 nanofibrous web composite membrane outperformed a single cell with a pristine Aquivion membrane in fully humidified conditions (100% RH at 75 and 90 degrees C). The Aquivion/phosphate-modified TiO2/ZrO2 nanofibrous web composite membrane showed the best single cell performance at all four testing conditions, including the fully humidified medium-temperature conditions (e.g., P-max = 1.18 W cm(-2) at 75 degrees C and 100% RH, and P-max = 0.97 W cm(-2) at 90 degrees C and 100% RH) and partially humidified high-temperature conditions (P-max = 0.45 W cm(-2) at 120 degrees C and 40% RH, and P-max = 0.21 W cm(-2) at 140 degrees C and 20% RH). The composite membrane also displayed excellent durability evidenced by the accelerated lifetime (ALT) test results. Overall, the phosphate-modified TiO2/ZrO2 nanofibrous web composite membrane enhanced the electrical properties and durability of the fuel cell, especially at high temperatures (>120 degrees C).</P>

A NANOFIBROUS OXIDE-CARBON COMPOSITE SUPPORT FOR A HIGHLY ACTIVE AND STABLE PEMFC CATHODE CATALYST

Yukwon JEON,Yunseong JI,Yong Il CHO,Chanmin LEE,Dae-Hwan PARK,Yong-Gun SHUL 한국신재생에너지학회 2018 AFORE Vol.2018 No.8

Poly(ether imide) nanofibrous web composite membrane with SiO₂/heteropolyacid ionomer for durable and high-temperature polymer electrolyte membrane (PEM) fuel cells

Lee, Chanmin,Na, Heesoo,Jeon, Yukwon,Jung Hwang, Ho,Kim, Hyun-Jong,Mochida, Isao,Yoon, Seong-Ho,Park, Joo-Il,Shul, Yong-Gun Elsevier 2019 Journal of industrial and engineering chemistry Vol.74 No.-

<P><B>Abstract</B></P> <P>Poly(ether imide) (PEI) membranes for polymer electrolyte membrane fuel cells (PEMFCs) are prepared by the electrospinning method. This approach produces a membrane with a high porosity and surface area that is suitable for accommodating proton-conducting materials. A composite membrane was prepared by impregnating the pores of the electrospun PEI membrane with Aquivion ionomer. Then, an inorganic proton conductor in the form of SiO<SUB>2</SUB>/heteropolyacid (HPA) nanoparticles was prepared by a microemulsion process and the particles added to the Aquivion ionomer. The membranes were characterized by field emission scanning electron microscopy (FE-SEM) and single-cell performance testing for PEMFC. The durability of the composite membrane was assessed via accelerated lifetime and on/off tests.</P> <P>The ionomer-impregnated electrospun PEI membrane showed good thermal stability, satisfactory mechanical properties, and high proton conductivity. The addition of the SiO<SUB>2</SUB>/HPA nanoparticles improved the proton conductivity of the composite membrane, thereby allowing the operating temperature in low humidity environments to be extended. The composite membrane exhibited promising properties for application in high-temperature PEMFCs.</P>

THERMOMECHANICAL STABLE FLEXIBLE SOLID OXIDE FUEL CELLS

Ok Sung Jeon,Jin Goo Lee,Ho Jung Hwang,Chanmin Lee,Oh Chan Kwon,Jeong Pil Kim,Yong Gun Shul 한국신재생에너지학회 2018 AFORE Vol.2018 No.8

발사체 개발 시험시설의 형상관리 방법론 개발

전찬민,최민찬,박태근,Jeon, Chanmin,Choi, Minchan,Park, Taekeun 한국건설관리학회 2023 한국건설관리학회 논문집 Vol.24 No.3

This study is a study to develop a configuration management methodology for efficient and systematic management in the event of configuration changes such as deformation, explosion, and remodeling of launch vehicle development test facilities, which are emerging as important national facilities in the era of full-scale space competition. Through the analysis of international standards for configuration management, a configuration management process framework to be applied to launch vehicle development test facilities is extracted, a survey was conducted on experts who performed life cycle engineering of launch vehicle development test facilities, and a configuration management methodology optimized for operation/management of domestic launch vehicle development test facilities was proposed. Identify the configuration for launch vehicle development test facilities, the configuration management manager, configuration management organization, and configuration management board approve/process the configuration changes, and after construction is completed according to design requirements, launch vehicle development test facilities try to manage the configuration in a controlled state.

CMA 인식을 통한 메모리 안전성 강화 연구

홍준화(Junwha Hong),박찬민(Chanmin Park),정성윤(Seongyun Jeong),민지운(Jiun Min),유동연(Dongyeon Yu),권용휘(Yonghwi Kwon),전유석(Yuseok Jeon) 한국정보보호학회 2022 情報保護學會誌 Vol.32 No.4

C/C++에는 다수의 메모리 취약점이 존재하며 ASan은 낮은 오버헤드와 높은 탐지율로 이러한 메모리 취약점을 탐지하기 위해 광범위하게 사용되고 있다. 그러나 상용 프로그램 중 다수는 메모리를 효율적으로 사용하기 위해 Custom Memory Allocator(CMA)를 구현하여 사용하며, ASan은 이러한 CMA로부터 파생된 버그를 대부분 탐지하지 못한다. 이를 극복하기 위해 본 연구에서는 LLVM IR 코드를 RNN 신경망에 학습하여 CMA를 탐지하고, ASan이 CMA를 식별할 수 있도록 수정하여 CMA로부터 파생된 메모리 취약점을 탐지할 수 있는 도구인 CMASan을 제안한다. ASan과 CMASan의 성능 및 CMA 관련 취약점의 탐지 결과를 비교·분석하여 CMASan이 낮은 실행시간 및 적은 메모리 오버헤드로 ASan이 탐지하지 못하는 메모리 취약점을 탐지할 수 있음을 확인하였다.