Synergistic Effect of Carbon Nanofiber/Nanotube Composite Catalyst on Carbon Felt Electrode for High-Performance All-Vanadium Redox Flow Battery

Park, Minjoon,Jung, Yang-jae,Kim, Jungyun,Lee, Ho il,Cho, Jeaphil American Chemical Society 2013 Nano letters Vol.13 No.10

<P>Carbon nanofiber/nanotube (CNF/CNT) composite catalysts grown on carbon felt (CF), prepared from a simple way involving the thermal decomposition of acetylene gas over Ni catalysts, are studied as electrode materials in a vanadium redox flow battery. The electrode with the composite catalyst prepared at 700 °C (denoted as CNF/CNT-700) demonstrates the best electrocatalytic properties toward the V<SUP>2+</SUP>/V<SUP>3+</SUP> and VO<SUP>2+</SUP>/VO<SUB>2</SUB><SUP>+</SUP> redox couples among the samples prepared at 500, 600, 700, and 800 °C. Moreover, this composite electrode in the full cell exhibits substantially improved discharge capacity and energy efficiency by ∼64% and by ∼25% at 40 mA·cm<SUP>–2</SUP> and 100 mA·cm<SUP>–2</SUP>, respectively, compared to untreated CF electrode. This outstanding performance is due to the enhanced surface defect sites of exposed edge plane in CNF and a fast electron transfer rate of in-plane side wall of the CNT.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-10/nl402566s/production/images/medium/nl-2013-02566s_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl402566s'>ACS Electronic Supporting Info</A></P>

Nanostructured Electrocatalysts for All-Vanadium Redox Flow Batteries.

Park, Minjoon,Ryu, Jaechan,Cho, Jaephil Wiley-VCH 2015 Chemistry - An Asian Journal Vol.10 No.10

<P>Vanadium redox reactions have been considered as a key factor affecting the energy efficiency of the all-vanadium redox flow batteries (VRFBs). This redox reaction determines the reaction kinetics of whole cells. However, poor kinetic reversibility and catalytic activity towards the V(2+) /V(3+) and VO(2+) /VO2 (+) redox couples on the commonly used carbon substrate limit broader applications of VRFBs. Consequently, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. In this Focus Review, recent progress on metal- and carbon-based nanomaterials as an electrocatalyst for VRFBs is discussed in detail, without the intention to provide a comprehensive review on the whole components of the system. Instead, the focus is mainly placed on the redox chemistry of vanadium ions at a surface of various metals, different dimensional carbons, nitrogen-doped carbon nanostructures, and metal-carbon composites.</P>

Effect of Fluoropolymer Assisted Transfer on Graphene Doping

Park, Minjoon,Kwon, Ki Chang,Hyeon Oh, Jeong,Kim, Yu Geun,Jang, Ho Won,Kim, Soo Young American Scientific Publishers 2017 Science of advanced materials Vol.9 No.5

Edge-halogenated graphene nanoplatelets with F, Cl, or Br as electrocatalysts for all-vanadium redox flow batteries

Park, Minjoon,Jeon, In-Yup,Ryu, Jaechan,Jang, Haeseong,Back, Jong-Beom,Cho, Jaephil Elsevier 2016 Nano energy Vol.26 No.-

<P><B>Abstract</B></P> <P>The catalytic activity of V<SUP>2+</SUP>/V<SUP>3+</SUP> and VO<SUP>2+</SUP>/VO<SUB>2</SUB> <SUP>+</SUP> redox couples on the halogen-doped graphene nanoplatelets (F-, Cl-, and Br-GNPs) is studied by ball-milling graphite flakes with fluorine (F<SUB>2</SUB>), chlorine (Cl<SUB>2</SUB>), and bromine (Br<SUB>2</SUB>) molecules, respectively. Using the edge-selectively halogenated graphene materials with different edge exfoliation degrees, the vanadium redox reactions can be significantly facilitated by having abundant edge defects with large surface area in the order: Br-GNP>Cl-GNP>F-GNP. The influence of halogen functionalization on graphene nanoplatelets towards vanadium redox couples is further confirmed by stack-type vanadium redox flow batteries that demonstrates better cell performance than graphene nanoplatelets without dopant at the edges. Notably, the Br-GNP showed unique electrochemical performance of increased initial charge/discharge capacity and improved rate capability, respectively. It was found that halogen doping on graphene-based materials can promote vanadium redox reactions by creating effective active sites, and the electrocatalytic activity is dependent on edge exfoliation degree and well-preserved basal planes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Edge-halogenated graphene nanoplatelets for vanadium redox reactions was studied. </LI> <LI> Halogen doping on graphene-based materials can promote vanadium redox reactions. </LI> <LI> A large degree of edge exfoliation by Br facilitates mass transport of vanadium ions. </LI> <LI> Br-GNP catalyst leads to decrease of cell overpotentials in VRFBs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Single crystalline pyrochlore nanoparticles with metallic conduction as efficient bi-functional oxygen electrocatalysts for Zn-air batteries

Park, Joohyuk,Risch, Marcel,Nam, Gyutae,Park, Minjoon,Shin, Tae Joo,Park, Suhyeon,Kim, Min Gyu,Shao-Horn, Yang,Cho, Jaephil Royal Society of Chemistry 2017 ENERGY AND ENVIRONMENTAL SCIENCE Vol.10 No.1

<P>Oxygen reduction reaction (ORR) or oxygen evolution reaction (OER) electrocatalysts including carbon-, non-precious metal-, metal alloy-, metal oxide-, and carbide/nitride-based materials are of great importance for energy conversion and storage technologies. Among them, metal oxides (<I>e.g.</I>, perovskite and pyrochlore) are known to be promising candidates as electrocatalysts. Nevertheless, the intrinsic catalytic activities of pyrochlore oxides are still poorly understood because of the formation of undesirable phases derived from the synthesis processes. Herein, we present highly pure single crystalline pyrochlore nanoparticles with metallic conduction (Pb2Ru2O6.5) as an efficient bi-functional oxygen electrocatalyst. Notably, it has been experimentally shown that the covalency of Ru-O bonds affects the ORR and OER activities by comparing the X-ray absorption near edge structure (XANES) spectra of the metallic Pb2Ru2O6.5and insulating Sm2Ru2O7for the first time. Moreover, we followed the interatomic distance changes of Ru-O bonds using<I>in situ</I>X-ray absorption spectroscopy (XAS) to investigate the structural stabilities of the pyrochlore catalysts during electrocatalysis. The highly efficient metallic Pb2Ru2O6.5exhibited outstanding bi-functional catalytic activities and stabilities for both ORR and OER in aqueous Zn-air batteries.</P>

Unveiling the Catalytic Origin of Nanocrystalline Yttrium Ruthenate Pyrochlore as a Bifunctional Electrocatalyst for Zn–Air Batteries

Park, Joohyuk,Park, Minjoon,Nam, Gyutae,Kim, Min Gyu,Cho, Jaephil American Chemical Society 2017 NANO LETTERS Vol.17 No.6

<P>Zn-air batteries suffer from the slow kinetics of oxygen reduction reaction (ORR) and/or oxygen evolution reaction (OER). Thus, the bifunctional electrocatalysts are required for the practical application of rechargeable Zn-air batteries. In terms of the catalytic activity and structural stability, pyrochlore oxides (A(2)[B(2-x)A(x)]O7-y) have emerged as promising candidates. However, a limited use of A-site cations (e.g., lead or bismuth cations) of reported pyrochlore catalysts have hampered broad understanding of their catalytic effect and structure. More seriously, the catalytic origin of the pyrochlore structure was not clearly revealed yet. Here, we report the new nano crystalline yttrium ruthenate (Y-2[Ru2-xYx]O7-y) with pyrochlore structure. The prepared pyrochlore oxide demonstrates comparable catalytic activities in both ORR. and OER, compared to that of previously reported metal oxide-based catalysts such as perovskite oxides. Notably, we first find that the catalytic activity of the Y-2[Ru2-xYx]O7-y is associated with the oxidations and corresponding changes of geometric local structures of yttrium and ruthenium ions during electrocatalysis, which were investigated by in situ X-ray absorption spectroscopy (XAS) in real-time. Zn-air batteries using the prepared pyrochlore oxide achieve highly enhanced charge and discharge performance with a stable potential retention for 200 cycles.</P>

Exploration of the Effective Location of Surface Oxygen Defects in Graphene-Based Electrocatalysts for All-Vanadium Redox-Flow Batteries

Park, Minjoon,Jeon, In-Yup,Ryu, Jaechan,Baek, Jong-Beom,Cho, Jaephil Wiley (John WileySons) 2015 Advanced energy materials Vol.5 No.5

Oxide Nanomembrane Hybrids with Enhanced Mechano- and Thermo-Sensitivity for Semitransparent Epidermal Electronics

Park, Minjoon,Do, Kyungsik,Kim, Jaemin,Son, Donghee,Koo, Ja Hoon,Park, Jinkyung,Song, Jun-Kyul,Kim, Ji Hoon,Lee, Minbaek,Hyeon, Taeghwan,Kim, Dae-Hyeong Wiley (John WileySons) 2015 Advanced healthcare materials Vol.4 No.7

<P>Oxide nanomembrane hybrids with enhanced mechano- and thermo-sensitivity for semitransparent epidermal electronics are developed. The use of nanomaterials (single wall nanotubes and silver nanoparticles) embedded in the oxide nanomembranes significantly enhances mechanical and thermal sensitivities. These mechanical and thermal sensors are utilized in wheelchair control and hypothermia detection, which are useful for patients with strokes.</P>

회생절차에서 의결권의 배제 – 미국의 논의를 중심으로 -

박민준(Park, Minjoon) 한국법학원 2020 저스티스 Vol.- No.181

회생절차에 있어서 채권자들에게 회생계획안에 대한 동의 여부에 관하여 의결권을 부여하여 절차에 중대한 영향을 미칠 수 있도록 한 것은 채권자들이 자신들의 채권 회수를 최대화하고자 하는 방향으로 의결권을 행사하면 그에 따라 채무자의 가치도 극대화될 수 있다는 점에 기초한 것으로도 볼 수 있다. 그런데, 실제로는 채권자들이 이러한 채권 회수의 최대화와는 다른 이유로 의결권을 행사하는 경우가 있을 수 있는바, 그러한 경우에는 채권자들의 집단적인 의결권 행사가 채무자의 가치 극대화로 이어지지 못하여 채무자나 다른 채권자들에게 불이익한 결과를 가져올 수 있을 것이다. 이러한 문제에 대하여는, 부당한 의결권자의 배제에 관한 채무자 회생 및 파산에 관한 법률 제190조의 규정을 통하여 어느 정도 대응할 수 있을 것으로 보인다. 다만, 그동안 위 규정에 따른 의결권의 배제가 실무상 활용된 사례는 거의 없었으나, 회생절차에 대한 인식의 변화 및 채무자의 인수에 대한 관심 증대 등에 비추어 채무자에 대한 채권을 취득한 자가 단순히 채권을 회수하는 것 이외의 목적을 가진 경우도 증가할 것으로 보이고, 이에 위 규정에 따라 의결권자의 의결권을 배제하여야 할 것인지 여부가 문제되는 사건들이 적지 않게 나타날 수 있을 것으로 예상된다. 이와 관련하여 위 규정과 어느 정도 유사성을 가지고 있는 미국 연방파산법 §1126(e)에 관한 논의를 참조할 수 있을 것으로 보인다. 즉, 위 연방파산법 규정에서는 회생계획안에 대한 채권자의 동의나 반대가 ‘성실’(good faith)하게 이루어지지 아니한 경우에는 의결권 행사가 배제될 수 있도록 하고 있다. 미국 법원에서 의결권 행사에 성실함이 결여되었다고 판단한 사례에는, 채권자가 그가 보유하고 있는 채권에 기하여 지급받을 수 있는 부분을 초과하는 급부를 지급받고자 한 경우, 채권의 매입이 채권자로서의 이해관계가 아닌 다른 이해관계를 조력하기 위한 것이었고 그와 같은 매입으로 인하여 차별적인 결과가 초래되는 경우, 채무자를 폐업시키고자 하였던 경우, 경쟁 관계에 있는 다른 회생계획안이 가결 요건을 갖추는 것을 막고자 채권을 매입한 경우, 채권자로서 채권 회수를 증대하려는 목적이 아니라 제3자와 체결한 별도 약정에 따른 이득을 얻고자 하였던 경우 등이 있었던 것으로 보인다. 이 글에서는 미국 연방파산법 §1126(e)에 대한 미국 법원의 결정례 및 해석론을 구체적으로 살펴보고, 그러한 내용이 우리나라의 회생절차에 어떠한 시사점을 가지는 것인지를 검토하여 보고자 한다. In Rehabilitation Procedure, enabling creditors to cast votes whether to accept the plan might be based on the assumption that if creditors vote to maximize their recovery on claims, then the value of the debtor could be maximized as well. However, in reality there could be some occasions where creditors who cast their votes for reasons other than maximizing their recovery on claims. On these occasions, collective voting of creditors would not lead to maximizing the value of the debtor which in turn would bring negative consequences to the debtor and other creditors. To deal with this problem, the court should use the Debtor Rehabilitation and Bankruptcy Act §190 under which the court may prohibit creditors who acquired their rights for the purpose of making unfair gains from exercising their voting rights. Although this provision has been rarely used in practice, there could be some cases in which the issue of excluding voting rights would arise since the number of creditors who acquired their rights based on interests other than recovering their rights is expected to increase due to the positively changed social attitudes to Rehabilitation Procedure and growing attention to acquiring debtors in Rehabilitation Procedure. In this context, it would be helpful to see the discussion over the United States Bankruptcy Code §1126(e), which is similar to the Debtor Rehabilitation and Bankruptcy Act §190 to some extent. Under the Bankruptcy Code §1126(e), the court may designate (disqualify) a vote that was not cast in “good faith.” It seems that courts in the United States found the lack of good faith in cases like where creditors had motive to extort beyond their rights, where buying claims resulted in unfair discrimination between selling and non-selling creditors, where creditors desired to destroy debtor’s business, where claim purchasing was intended to block the confirmation of another competing plan, and where creditors were not motivated by increasing recovery on claims but by benefiting from the agreement with third party. This paper will try to introduce court decisions and interpretations on the Bankruptcy Code §1126(e), and review what implications those decisions and interpretations have in Rehabilitation Procedure in Korea.

고성능 리튬 금속 음극을 위한 제작 공정과 전략

박지한 ( Jihan Park ),김주은 ( Jueun Kim ),최지원 ( Jiwon Choi ),강지현 ( Jihyeon Kang ),박민준 ( Minjoon Park ) 한국공업화학회 2023 공업화학전망 Vol.26 No.5

리튬 금속 전지는 높은 에너지 밀도를 기반으로 기존의 리튬 이온 전지를 대체할 수 있는 소자로 각광받고 있다. 그러나 Li plating/stripping 동안 리튬의 큰 부피 변화와 불균일한 Li+ flux에 의해 유도된 고립 및 수지상 리튬은 리튬 금속 전지의 실질적인 적용을 방해한다. 특히 리튬 이온 전지의 음극용 집전체로 널리 사용되는 구리 호일은 리튬 친화성이 열악하여 리튬 금속 전지에서 성능 열화의 주요 원인이 된다. 리튬 금속 전지의 수명 특성을 향상시키기 위해 리튬의 반복적인 부피 팽창을 수용하고 리튬 친화성을 개선하기 위해 3차원 구조체를 도입하거나 구리의 표면을 개질하는 연구들이 활발히 수행되고 있음에도 불구하고 리튬 금속 음극을 제작하는 방법은 정립되어 있지 않은 실정이다. 본 기고문에서는 리튬 금속 음극을 제작하기 위한 새로운 방법들, 고려되어야 할 요인들과 공정의 확장 가능성을 시사하고 구리 집전체들의 리튬 친화성을 크게 향상시킨 최근 전략들을 소개하고자 한다.