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09월 12일 17시 이후 : 초록수정 불가능, 일정확인 및 검색만 가능
제110회 대한화학회 학술발표회, 총회 및 기기전시회 안내
Hydrogen storage system based on dehydrogenation of metal hydride: The effect of Pd nanoparticles on the decomposition of borohydrides in homogeneous solution
2012년 8월 24일 09시 56분 48초
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10월 17일 (수요일) 16:00~19:00
고려대학교 소재화학과, Korea
한국과학기술연구원 연료전지센터, Korea
Complex hydrides such as borohydrides (BH4?) attracted considerable attention due to their high storage capacities. Among them, LiBH4 with a high theoretical storage capacity of 18.5 wt.% of H2, has been considered as a good candidate for on-board applications. However, extraction of hydrogen from LiBH4 suffers due to the onset temperature of LiBH4 decomposition of ca. 400 °C and only half of the hydrogen being released below 600 °C. Consequently, recent research has focused on the catalyzed dehydrogenation of borohydrides (BH4?) in order to lower the H2 evolution temperature and to increase the hydrogen desorption capacity. This is mainly due to the various complicated interactions involved in the solid state reactions in general: e.g. (a) chemical reactions of reactants and catalyst; (b) physical interactions in the solid state transformations, such as nucleation and growth, phase transformation and diffusion of molecules and atoms. In the present study we carried out the reactions under the homogeneous condition in solution phase. Tetraglyme (TG) was used as a solution matrix for homogeneous dehydrogenation because of its high boiling point (270 °C), the thermal stability and the solubility of borohyrides. We show the pressure change upon heating of LiBH4 solutions without additives. While the solid LiBH4 exhibits an decomposition at 400 °C, the onset temperatures of LiBH4 in TG are 250 °C. However, the molar ratio of released H2 to starting LiBH4 is about 3.4:1, which is larger than the nominal ratio (1.5:1). We attributed the excessive hydrogen to the side reaction of NaH or Al with the TG solvent. It is known that a transition metal species enhances the dehydrogenation of LiBH4 in solid state. We carried out the dehydrogenation in solution in order to examine if the palladium nanoparticles (PdNPs) enhances the reaction under homogeneous condition as in solid state. The results show that the PdNPs enhances the reaction in solution, the onset temperature of LiBH4 with PdNPs in TG is 220 °C. One and two-dimensional solid-state 11B-NMR spectra of the LiBH4 spent fuel (LiBHx) sorted out all non-equivalent boron sites and classified them into B3 (SP2)and B4 (SP3) borons and the SP2 boron sites are rather similar to SP2 boron of B-O coordination. In addition, there are significant amount of organic species co-precipitated with LiBHx.
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