Electrospun Poly(vinylidene fluoride)-based Carbon Nanofibers for Hydrogen Storage
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Electrospun Poly(vinylidene fluoride)-based Carbon Nanofibers for Hydrogen Storage H. J. Chung1 , D. W. Lee1, S. M. Jo, D. Y. Kim, and W. S. Lee Polymer Hybrid Research Center, Korea Institute of Science and Technology, 39-1, Hawolgok dong, Seongbuk-gu, Seoul 136-791, Republic of Korea 1 Department of Chemical Engineering, University of Seoul, Jeonnong-Dong, Dongdeamun-Gu, Seoul 130-743, Republic of Korea ABSTRACT Poly(vinylidene fluoride) (PVdF) fine fiber of 200-300 nm in diameter was prepared through the electrospinning process. Dehydrofluorination of PVdF-based fibers for making infusible fiber was carried out using DBU, and the infusible PVdF-based nanofibers were then carbonized at 900-1800oC. The structural properties and morphologies of the resulting carbon nanofibers were investigated using XRD, Raman IR, SEM, TEM, and surface area & pore analysis. The PVdF-based carbon nanofibers had rough surfaces composed of 20to 30-nm granular carbons, indicating their high surface area in the range of 400-970 m2/g. They showed amorphous structures. In the case of the highly ehydrofluorinated PVdF fiber, the resulting carbon fiber had a smoother surface, with d002 = 0.34-0.36 nm, and a very low surface area of 16-33 m2/g. The hydrogen storage capacities of the above carbon nano-fibers were measured, using the gravimetric method, by magnetic suspension balance (MSB), at room temperature and at 100 bars. The storage data were obtained after the buoyancy correction. The PVdF-based microporous carbon nanofibers showed a hydrogen storage capacity of 0.04-0.4 wt%. The hydrogen storage capacity depended on the dehydrofluorination of the PVdF nanofiber precursor, and on the carbonization temperatures. INTRODUCTION Since the physical adsorption of hydrogen gas at the interface of carbon materials will be higher than the bulk due to the Van der Waals interactions, much researches on hydrogen storage using single wall nanotubes(SWNT), multiwall nanotubes(MWNT), graphite nano-fibers(GNF), active carbon, active carbon fiber, graphite powder, etc., have been done. Since Dillon first reported the excellent 6- to 8-wt% hydrogen storage capacity of SWNT at room temperature and with atmospheric pressure [1], Liu observed the hydrogen adsorption of 4.2-wt% (0.5-H/C) SWNT at 100 bars and at room temperature using SWNT synthesized through the arc electric discharge method [2]. Zhu et al., reported a hydrogen adsorption of about 3 wt% at 3-100 MPa, and at room temperature, using a well-aligned SWNT bundle [3]. On the other hand, purified SWNT (285 m2/g) and saran carbon (1600 m2/g) with a high BET surface area were also reported to have a hydrogen adsorption of about 0.04 H/C and 0.28 H/C at 0.32 MPa, 80 K, respectively [4]. Nijkamp et al.[5] also discovered a large hydrogen adsorption by a microporous zeolite and active carbons at 77K and at atmospheric pressure. Chahine et al. [6] reported a very high hydrogen adsorption of 5.3 wt% (0.64 H/C) at 77K and at 1 MPa, in the highly porous
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carbon (AX-21 carbon). Despite the l
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