https://scholar.gist.ac.kr/handle/local/7966 2025-12-08T05:04:57Z 2025-12-08T05:04:57Z 조영훈 https://scholar.gist.ac.kr/handle/local/19904 2025-06-30T12:13:26Z 2024-12-31T15:00:00Z

Title: 직접 암모니아 연료전지의 Perovskite 구조 기반 Anode의 B-site 화학양론 제어를 통한 성능 개선 연구 Author(s): 조영훈 Abstract: Ammonia has high energy density and the advantage of utilizing existing infrastructure, making it increasingly significant as a direct fuel for energy production in solid oxide fuel cell (SOFC). However, ammonia-fueled SOFC have a lower power density compared to hydrogen fuel cells. To address this issue, this study investigates Sr2Fe1.6M0.5O6-δ, an electrode material based on Sr2Fe1.5M0.5O6-δ with high conductivity and stability under reducing environments, by further increasing the Fe content. The structural stability and the formation of Fe nanoparticles on the electrode surface were confirmed through XRD, SEM, and TEM analyses. The electrochemical performance and catalytic properties of the fuel cells were evaluated. As the Fe content increased, more Fe nanoparticles were formed under reducing conditions, enhancing both electrochemical and catalytic performance. Notably, the electrochemical performance of the DA-SOFC increased by approximately 2.4 times, achieving performance comparable to fuel-electrode-supported DA-SOFCs. In conclusion, this study demonstrates a viable solution to overcome the performance limitations of oxide electrode as anode.

2024-12-31T15:00:00Z HyunWoo Choi https://scholar.gist.ac.kr/handle/local/31979 2025-09-08T02:51:19Z 2024-12-31T15:00:00Z

Title: 연료극 지지형 고체산화물 셀의 제조과정에 따른 전기화학적 성능 최적화 및 열화 메커니즘 분석 Author(s): HyunWoo Choi Abstract: Solid Oxide Cells (SOCs) are promising high-temperature electrochemical devices that offer high energy conversion efficiency and operate without the need for noble metal catalysts, enabling cost-effective and environmentally friendly energy systems. Hydrogen, as a clean fuel, can be utilized to generate electricity in SOCs. Yttria-Stabilized Zirconia (YSZ) is commonly used as an oxygen ion-conducting electrolyte, and Ni-based cermets are typically employed as fuel electrodes. SOCs utilizing a Ni cermet-supported anode allow for the application of thin electrolytes, thereby significantly reducing ohmic resistance and enhancing power density. However, when ZrO₂-based electrolytes are used, the interdiffusion of La and Sr from the cathode can result in the formation of secondary phases such as LaZrO₃, SrZrO₃, and La₂Zr₂O₇, which degrade ionic conductivity and increase interfacial resistance. To mitigate such reactions, a barrier layer such as Gd₂O₃-doped CeO₂ (GDC) is typically introduced between the electrolyte and cathode, requiring high-temperature co-sintering (1250°C– 1450°C). However, the co-sintering process may also induce undesired reactions between GDC and YSZ, forming secondary phases such as Gd₂Zr₂O₇, which deteriorate electrochemical performance. Additionally, Ni diffusion from the anode into the YSZ electrolyte can lead to phase instability and degradation in conductivity during long- term operation. Despite these challenges, there is limited research addressing processing strategies to suppress interfacial reactions during co-sintering, as well as the impact of Ni diffusion on the ionic conductivity and structural stability of YSZ electrolytes. Therefore, this study aims to investigate the effects of post-sintering treatments at reduced temperatures—enabled through compositional modifications—on the suppression of secondary phase formation and to evaluate the electrochemical performance and degradation mechanisms resulting from Ni diffusion in YSZ-based electrolytes.

2024-12-31T15:00:00Z 이동열 https://scholar.gist.ac.kr/handle/local/19902 2025-06-30T12:13:23Z 2024-12-31T15:00:00Z

Title: 비백금 음이온 교환막 수전해를 위한 철 도핑 활용 니 켈-몰리브데넘 합금 촉매의 활성점 제어 Author(s): 이동열 Abstract: Developing advanced catalysts for the hydrogen evolution reaction in alkaline media remains a significant hurdle for the broader adoption of anion exchange membrane water electrolyzers. This study presents the synthesis of an Fe-doped Ni4Mo/MoOx catalyst through a synergistic approach involving hydrothermal and thermal reduction processes. Material characterization and electron structure analysis underscored the pivotal role of Fe, and its addition notably promoted the formation of the Ni4Mo phase, which was identified as active site of the catalyst. Further insights from density functional theory calculations revealed that Fe doping enhanced the desorption energy necessary for the H2 recombination step within the Ni4Mo phase, bolstering both the intrinsic and extrinsic activities. This enhancement propelled the NiMoFe catalyst to outperform conventional NiMo catalysts in both aqueous model system and membrane electrode assembly experiment. Notably, an anion exchange membrane water electrolysis configured with the NiMoFe catalyst at the cathode demonstrated remarkable performance, reaching a cell voltage of 1.63 V at a current density of 1 A cm-2, and preserving over 98% of its initial voltage at 0.5 A cm-2, demonstrating its potential for commercial applications.

2024-12-31T15:00:00Z 남가은 https://scholar.gist.ac.kr/handle/local/19860 2025-06-30T12:12:22Z 2021-12-31T15:00:00Z

Title: Trophic contribution of subtidal benthic microalgae to macrobenthic food web in a shallow temperate coastal zone: an isotopic approach Author(s): 남가은 Abstract: The role of subtidal benthic microalgae to the trophic base of benthic food web has been a challenging subject because of difficulties in collecting separately from the surface sediment and qualitatively and quantitatively assessing interactions between producers and consumers. In the present study, macroinvertebrates were collected at two respective sites in the shallow subtidal zone off the Tongyeong and Jeju Island coasts and their stable carbon and nitrogen isotope ratios (δ13C and δ15N, as trophic biomarkers) were determined to evaluate the trophic importance of benthic microalgae to benthic food web across the nearshore shallow coastal ecosystems. Suspended particulate organic matter (POM), sedimentary organic matter (SOM), phytoplankton, and benthic microalgae (as potential food sources) as well as zooplankton (as a phytoplankton-reliance measure) were also collected. A permutational multivariate analysis of variance revealed no significant differences in isotope values of potential food sources between two locations. An analysis of variance exhibited that the δ13C values of potential sources were readily distinguishable between benthic microalgae and the other pelagic components (POM and phytoplankton), allowing us to track their nutritional contribution to consumer production. Based on the δ13C and δ15N values of consumers, a self-organizing map and following cluster analysis clearly separated between suspension feeders and deposit feeders in both locations. The δ13C values of predators displayed a broad range, overlapping with those of primary consumers, and their δ15N values were higher than those of the latter, suggesting that they occupy the higher trophic position. The MixSiAR mixing-model calculations revealed that the contribution of pelagic sources (POM and phytoplankton) was predominant to the suspension-feeding group and benthic microalgae was prevalent to the deposit-feeding group in both the shallow subtidal areas. The contribution of benthic microalgae to the nutrition of predators was estimated to be considerable. Overall, this study demonstrates the merit of stable isotope approach that lays a cornerstone for highlighting the trophic importance of benthic microalgae to shallow subtidal benthic food web on the basis of understanding the strength of producer-consumer interactions and trophic pathways.|연안역 조하대 저서먹이망의 영양기저에 대한 저서미세조류의 역할은 퇴적물 표면으로부터 추출 채집의 어려움과 함께 생산자와 소비자 동물군 사이의 상호작용을 정성ˑ정량적으로 평가하는 방법상의 어려움에 기인하여 연구하기 어려운 난제로 여겨져 왔다. 본 연구에서는 통영과 제주도 연안의 연안 천해 조하대 각각 2개 정점에서 저서 대형 무척추동물을 채집하고 이들 저서생태계 먹이망에 대한 저서미세조류의 기여를 평가하기 위하여 생체지표로써 탄소와 질소 안정동위원소 비값(δ13C와 δ15N)을 측정하였다. 잠재 먹이원으로 부유입자유기물질, 퇴적유기물, 식물플랑크톤 및 저서미세조류을 채집하고 비교를 위하여 식물플랑크톤 섭식자로써 동물플랑크톤 시료를 함께 채집하였다. 비모수 다변량 분석(permutational multivariate analysis of variance)의 결과는 두 연안역에서 잠재먹이원의 동위원소 비값에서 유의한 차이가 없다는 것을 밝혔다. 분산분석(analysis of variance)는 먹이원의 탄소안정동위원소 비값(δ13C)이 저서미세조류와 다른 먹이원들과 뚜렷히 구분된다는 것을 나타내어 소비자 동물군 영양에 대한 기여를 추정할 수 있도록 해 주었다. 동물체의 탄소와 질소 안정동위원소 비값을 기초로 했을 때, 자기조직화 지도분석(self-organizing map, SOM)과 계층적 집괴분석(cluster analysis)는 부유물섭식자 동물군과 퇴적물섭식자 동물군을 잘 구분하여 주었다. 육식동물군의 탄소안정동위원소 비값(δ13C)은 생산자의 값 범위에 상당하는 넓은 범위에 분포하였고, 질소안정동위원소 비값(δ15N)은 생산자에 비하여 동물군들에서 높은 동위원소 비값의 영양단계 효과를 잘 반영하였다. 동위원소 혼합모델(MixSiAR mixing-model) 결과는 표영생산(부유입자물질과 식물프랑크톤)이 부유물섭식자의 주요 먹이원으로 작용하고, 저서미세조류는 퇴적물식자의 중요한 먹이원으로써의 역할을 한다는 것을 밝혔다. 육식성동물군에 대한 저서미세조류의 영양 기여가 상당한 것으로 나타났다. 본 연구는 생산자와 소비자동물군의 상호작용의 강도와 영양 경로에 대한 이해를 기반으로 천해 조하대 먹이망에 대한 저서미세조류의 영양 기여를 밝힐 수 있는 하나의 초석을 마련하는데 있어서 안정동위원소 분석의 가치를 입증해 주었다.

2021-12-31T15:00:00Z