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유기 리간드 제어를 통한 고분산 팔라듐 나노 촉매의 합성 및 음이온교환막 연료전지를 위한 산소 환원 반응 특성 분석
성후광,장정희,정남기,Sung, Hukwang,Sharma, Monika,Jang, Jeonghee,Jung, Namgee 한국재료학회 2018 한국재료학회지 Vol.28 No.11
In anion exchange membrane fuel cells, Pd nanoparticles are extensively studied as promising non-Pt catalysts due to their electronic structure similar to Pt. In this study, to fabricate Pd nanoparticles well dispersed on carbon support materials, we propose a synthetic strategy using mixed organic ligands with different chemical structures and functions. Simultaneously to control the Pd particle size and dispersion, a ligand mixture composed of oleylamine(OA) and trioctylphosphine(TOP) is utilized during thermal decomposition of Pd precursors. In the ligand mixture, OA serves mainly as a reducing agent rather than a stabilizer since TOP, which has a bulky structure, more strongly interacts with the Pd metal surface as a stabilizer compared to OA. The specific roles of OA and TOP in the Pd nanoparticle synthesis are studied according to the mixture composition, and the oxygen reduction reaction(ORR) activity and durability of highly-dispersed Pd nanocatalysts with different particles sizes are investigated. The results of this study confirm that the Pd nanocatalyst with large particles has high durability compared to the nanocatalyst with small Pd nanoparticles during the accelerated degradation tests although they initially indicated similar ORR performance.
음이온 교환막의 정확한 OH<sup>-</sup>전도도 및 CO<sub>2</sub> 피독 효과 분석을 위한 전기화학적 측정법
김수연,권후근,이혜진,정남기,배병찬,신동원,Kim, Suyeon,Kwon, Hugeun,Lee, Hyejin,Jung, Namgee,Bae, Byungchan,Shin, Dongwon 한국전기화학회 2022 한국전기화학회지 Vol.25 No.2
The anion exchange membrane used in alkaline membrane fuel cells transports hydroxide ions, and ion conductivity affects fuel cell performance. Thus, the measurement of absolute hydroxide ion conductivity is essential. However, it is challenging to accurately measure hydroxide ion conductivity since hydroxide ions are easily poisoned in the form of bicarbonate by carbon dioxide in the atmosphere. In this study, we applied electrochemical ion exchange treatment to measure the absolute hydroxide ion conductivity of the anion exchange membrane. In addition, we investigated the effect of carbon dioxide poisoning of hydroxide ions on electrochemical performance by measuring bicarbonate conductivity. Commercial anion exchange membranes (FAA-3-50 and Orion TM1) and polyphenylene-based block copolymer (QPP-6F) were used.
다공성 탄소층이 코팅된 하이브리드 표면 구조를 갖는 산소 환원 반응용 PtCo 합금 나노 촉매
장정희,모니카 샤르마,성후광,김순표,정남기,Jang, Jeonghee,Sharma, Monika,Sung, Hukwang,Kim, Sunpyo,Jung, Namgee 한국재료학회 2018 한국재료학회지 Vol.28 No.11
During a long-term operation of polymer electrolyte membrane fuel cells(PEMFCs), the fuel cell performance may degrade due to severe agglomeration and dissolution of metal nanoparticles in the cathode. To enhance the electrochemical durability of metal catalysts and to prevent the particle agglomeration in PEMFC operation, this paper proposes a hybrid catalyst structure composed of PtCo alloy nanoparticles encapsulated by porous carbon layers. In the hybrid catalyst structure, the dissolution and migration of PtCo nanoparticles can be effectively prevented by protective carbon shells. In addition, $O_2$ can properly penetrate the porous carbon layers and react on the active Pt surface, which ensures high catalytic activity for the oxygen reduction reaction. Although the hybrid catalyst has a much smaller active surface area due to the carbon encapsulation compared to a commercial Pt catalyst without a carbon layer, it has a much higher specific activity and significantly improved durability than the Pt catalyst. Therefore, it is expected that the designed hybrid catalyst concept will provide an interesting strategy for development of high-performance fuel cell catalysts.
고분자전해질연료전지 연료극의 이오노머 함량에 따른 CO 내피독 특성 연구
김도열(Doyeol Kim),우승희(Seunghee Woo),박석희(Seok-Hee Park),정남기(Namgee Jung),임성대(Sung-Dae Yim) 한국신재생에너지학회 2018 신재생에너지 Vol.14 No.4
This paper reports the effects of the ionomer content on CO tolerance in a PtRu/C-based anode catalyst layer to understand the role of ionomer binders for CO poisoning of the electrocatalyst and to design a durable catalyst layer of MEA. Four different MEAs were prepared with ionomer contents of 20, 30, 40, and 50 wt. % for the anode and a fixed ionomer content of 30 wt. % for the cathode. The MEA performance was then tested under hydrogen and CO mixed gas feeding in a single cell to observe the CO tolerance of the prepared MEAs. The MEA performance was largely dependent on the anode ionomer content under both hydrogen and CO mixed gas conditions, revealing the best cell performance at a 40 wt. % ionomer content. The MEA also showed the lowest cell potential decay under CO mixed gas compared to hydrogen at a 40 wt. % ionomer content. The present study provides insights into the design of an anode catalyst layer structure, including optimization of the ionomer content, which can be critical to the design of a high performance MEA for reformed gas applications.
리튬 이차전지용 전극 및 연료전지 촉매 소재 연구 개발 동향
윤홍관(Hongkwan Yun),김다희(Dahee Kim),김천중(Chunjoong Kim),김용진(Young-Jin Kim),민지호(Ji Ho Min),정남기(Namgee Jung) 한국세라믹학회 2018 세라미스트 Vol.21 No.4
In this paper, we review about current development of electrode materials for Li-ion batteries and catalysts for fuel cells. We scrutinized various electrode materials for cathode and anode in Li-ion batteries, which include the materials currently being used in the industry and candidates with high energy density. While layered, spinel, olivine, and rock-salt type inorganic electrode materials were introduced as the cathode materials, the Li metal, graphite, Li-alloying metal, and oxide compound have been discussed for the application to the anode materials. In the development of fuel cell catalysts, the catalyst structures classified according to the catalyst composition and surface structure, such as Pt-based metal nanoparticles, non-Pt catalysts, and carbon-based materials, were discussed in detail. Moreover, various support materials used to maximize the active surface area of fuel cell catalysts were explained. New electrode materials and catalysts with both high electrochemical performance and stability can be developed based on the thorough understanding of earlier studied electrode materials and catalysts.
대면적 분리판의 운전 환경 불균일성을 고려한 MEA 성능최적화 방법
김성민(Sungmin Kim),손영준(Young-Jun Sohn),우승희(Seunghee Woo),박석희(Seok-Hee Park),정남기(Namgee Jung),임성대(Sung-Dae Yim) 한국신재생에너지학회 2021 신재생에너지 Vol.17 No.2
We proposed an MEA development methodology that accurately measures intrinsic MEA performance while considering the uneven reaction environments formed inside a large-area BP. To facilitate measurement of the inherent MEA performance, we miniaturized the active area of the MEA to 3 cm², and prepared two MEAs with different ionomer contents of 0.65 and 0.80 (I/C). By simulating the operating conditions of a 100 cm² BP at the inlet (I), center (C), and outlet (O), the oxygen concentration and relative humidity were determined to be 20.7, 13.8, 11.7%, and 50, 66.1, and 70.1% respectively. We measured the performance and electrochemical analysis of the prepared MEAs under the three simulated conditions. Based on the results of statistical analysis of the evaluated MEA performance data, I/C 0.65 MEA had a higher average performance and lower performance deviation than I/C 0.80 MEA. Hence, it can be concluded that an I/C 0.65 MEA is a more effective MEA for large-area BP. Based on the above research process, we confirmed the effectiveness of the proposed MEA development methodology.