https://scholar.korea.ac.kr/handle/2021.sw.korea/2596 Thu, 09 Apr 2026 10:12:44 GMT 2026-04-09T10:12:44Z https://scholar.korea.ac.kr/handle/2021.sw.korea/72524 Title: A viable membrane reactor option for sustainable hydrogen production from ammonia Authors: Jo, Young Suk; Cha, Junyoung; Lee, Chan Hyun; Jeong, Hyangsoo; Yoon, Chang Won; Nam, Suk Woo; Han, Jonghee Abstract: Conventional hydrogen production from ammonia is both energy and process intensive, requiring high temperature and independent purification units. Here, we present a compact process of energy conversion from NH3 to electricity using a novel membrane reactor, comprised of a dense metallic Pd/Ta composite membrane and Ru/La-Al2O3 pellet catalysts, and a fuel cell unit. The fabricated Pd/Ta composite membrane, having ca. 5 times higher H-2 permeability than conventional Pd-Ag membranes, can both lower NH3 dehydrogenation temperature and completely remove an additional hydrogen purification unit. Compared to a packed-bed reactor without membrane, ammonia conversion improves by 75 and 45%, respectively at 425 and 400 degrees C, and > 99.5% of conversion is achieved at 450 degrees C under pressurized ammonia feed of 6.5 bar. Main barriers of practical application of Pd/Group V metals as a composite hydrogen permeable membrane, embrittlement and durability issues, are overcome owing to pertinent operating temperatures (400-450 degrees C) of ammonia dehydrogenation coupled with membrane separation. Finally, as-separated hydrogen with < 1 ppm of NH3 is provided directly to a polymer electrolyte membrane fuel cell, showing no performance degradation for an extended time of operation. The combined results suggest a feasible and less energy/process intensive option for producing hydrogen or electricity from ammonia. Mon, 01 Oct 2018 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/72524 2018-10-01T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/81235 Title: Novel Fabrication of Porous Ni-5 wt.% Al Alloy Electrode Below the Melting Point of Aluminum Authors: Ham, Hyung Chul; Choi, Sun Hee; Jang, Seong-Cheol; Song, Shin Ae; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo Abstract: An in-situ sintered Ni-5 wt.% Al alloy anode for high-temperature fuel cells (HTFCs) was fabricated successfully using a green sheet consisting of a physical mixture of inexpensive Ni and Al elemental powders at reduced temperatures. Two processes-the formation of Ni-Al alloy via the AlCl3 activator under flowing hydrogen gas and the sintering of Ni-Al-occurred at the same time during pretreatment for cell operation. The AlCl3 activator reduced the synthesis reaction temperature and sintering temperature of Ni-Al alloy to nearly 600 degrees C. A two-phase alloy of a Ni3Al intermetallic compound and a Ni-Al solid solution was obtained after sintering at 600 degrees C. The creep resistance of the in-situ sintered Ni-5 wt.% Al alloy was better than that of the conventional Ni-Al alloy green sheet, even though the sintering temperature of the Ni-5 wt.% Al alloy was 600 degrees C. This novel preparation method for Ni-Al alloys can greatly reduce the cost of anode fabrication for HTFCs and in turn accelerate the commercialization of HTFCs. Fri, 01 Dec 2017 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/81235 2017-12-01T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/83413 Title: Ultrathin layered Pd/PBI-HFA composite membranes for hydrogen separation Authors: Kong, Seong Young; Kim, Da Hye; Henkensmeier, Dirk; Kim, Hyoung-Juhn; Ham, Hyung Chul; Han, Jonghee; Yoon, Sung Pil; Yoon, Chang Won; Choi, Sun Hee Abstract: Generally, Pd membranes used for H-2 purification are deposited on porous stainless steel (SS) or porous ceramics. These membranes are thick ( > 5 mu m) because of the large pore size of the support used; hence, such thick membranes are not cost-effective. In this study, cost-effective, viable ultrathin Pd membranes, which were deposited on a polymer substrate, e.g., polybenzimidazole-4,4'-(hexafluoroisopropylidene) bis(benzoic acid) (PBI-HFA), with a thickness less than 700 nm, were prepared by vacuum electroless plating (VELP). The estimated thickness and effective permeation area of the Pd/PBI-HFA membranes were 130-656 nm and 8.3 cm(2), respectively. An optimum Pd/PBI-HFA membrane was deposited after two times activation (A2). Because of the adequate grain size of Pd crystals and thickness, Pd/PBI-HFA exhibited better hydrogen permselectivity than the samples prepared by one and three times activation. Furthermore, the polymer surface treated by the CO2 plasma (CO2) and oxidation by H2O2 (H) leads to the enhanced selectivity performance of the final Pd/PBI-HFA membrane, caused by the enhanced adhesion between Pd and PBI-HFA. Gas permeation properties of H-2, N-2, CO2, and CO were evaluated between 35 and 200 degrees C and pressure differences between 4 and 8 bar. Pd films fabricated by A2 -CO2 methods exhibited superior performance, as well as excellent alpha(H2/N2) and alpha(H2/CO2), permselectivities of 41.4 and 22.3, respectively, at 150 degrees C and 8 bar, and proved to be impermeable to carbon monoxide (CO). It is a 48% increase in the alpha(H2/N2) permselectivity and fourfold increase in the alpha(H2/CO2)., permselectivity from bare PBI-HFA membrane. In this study, an effective Pd layer was deposited on PBI-HFA under optimum Pd electroless plating conditions by controlling the interface adhesion strength and distribution of Pd seeds on the substrate.(C) 2017 Elsevier B.V. All rights reserved. Wed, 31 May 2017 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/83413 2017-05-31T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/7709 Title: Transforming Global Governance with Middle Power Diplomacy: South Korea's Role in the 21st Century Authors: Sungjin Kim Fri, 01 Jul 2016 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/7709 2016-07-01T00:00:00Z