Large Surface Area Ordered Porous Carbons via Nanocasting Zeolite 10X and High Performance for Hydrogen Storage Application

Abstract

ABSTRACT:We report the preparation of ordered porous carbons for the first time via nanocasting zeolite 10X with an aim to evaluate their potential application for hydrogen storage. The synthesized carbons exhibit large Brunauer-Emmett-Teller surface areas in the 1300−3331 m 2 /g range and pore volumes up to 1.94 cm 3 /g with a pore size centered at 1.2 nm. The effects of different synthesis processes with pyrolysis temperature varied in the 600−800°C range on the surface areas, and pore structures of carbons were explored. During the carbonization process, carbons derived from the liquid−gas two-step routes at around 700°C are nongraphitic and retain the particle morphology of 10X zeolite, whereas the higher pyrolysis temperature results in some graphitic domains and hollow-shell morphologies. In contrast, carbons derived from the direct acetylene infiltration process have some incident nanoribbon or nanofiber morphologies. A considerable hydrogen storage capacity of 6.1 wt % at 77 K and 20 bar was attained for the carbon with the surface area up to 3331 m 2 /g, one of the top-ranked capacities ever observed for large surface area adsorbents, demonstrating their potential uses for compacting gaseous fuels of hydrogen. The hydrogen capacity is comparable to those of previously reported values on other kinds of carbon-based materials and highly dependent on the surface area and micropore volume of carbons related to the optimum pore size, therefore providing guidance for the further search of nanoporous materials for hydrogen storage. KEYWORDS: porous carbons, adsorption, nanocasting, zeolite template, hydrogen storage ■ INTRODUCTIONRecently, hydrogen as an alternative to fossil fuel has been recognized as an attractive energy carrier and fuel in the near future because it has high energy densities and creates neither air pollution nor greenhouse gas emissions.1−3 The main drawback for hydrogen as a transportation fuel is the lack of an effective storage method, which is yet to reach the criterions set by the DOE (Department of Energy, USA) for on-board application. Hence the development of cost-effective and feasible materials to satisfy on-board application claim for hydrogen storage is a great challenge. 4−7 Up to now, large numbers of adsorbents have been under intensive studies for hydrogen storage, and porous carbons with high surface areas and large pore volumes are considered as promising candidates for application as the hydrogen storage media. 8−12 The wide pore size distributions (PSDs) of conventional activated carbons in both the micro-and mesopore ranges will greatly affect their storage performance.13 Therefore, it is not difficult to imagine that preparation of carbons with a narrow PSD is very important in determining their adsorption performance. The template carbonization route is a versatile and well fitted methodology for the preparation of porous materials especially for the carbon-based materials with a controlled architecture and relative narrow PSD. 11,14−16 The template method usually...

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