Preparation and hydrogen storage properties of zeolite-templated carbon materials nanocast via chemical vapor deposition: effect of the zeolite template and nitrogen doping.
Carbon materials have been prepared using zeolite 13X or zeolite Y as template and acetonitrile or ethylene as carbon source via chemical vapor deposition (CVD) at 550-1000 degrees C. Materials obtained from acetonitrile at 750-850 degrees C (zeolite 13X) or 750-900 degrees C (zeolite Y) have high surface area (1170-1920 m(2)/g), high pore volume (0.75-1.4 cm(3) g(-1)), and exhibit some structural ordering replicated from the zeolite templates. Templating with zeolite Y generally results in materials with higher surface area. High CVD temperature (> or =900 degrees C) results in low surface area materials that have significant proportions of graphitic carbon and no zeolite-type structural ordering. The nitrogen content of the samples derived from acetonitrile varies between 5 and 8 wt %. When ethylene is used as a carbon precursor, high surface area (800-1300 m(2)/g) materials are only obtained at lower CVD temperature (550-750 degrees C). The ethylene-derived carbons retain some zeolite-type pore channel ordering but also exhibit significant levels of graphitization even at low CVD temperature. In general, the carbon materials retain the particle morphology of the zeolite templates, with solid-core particles obtained at 750-850 degrees C while hollow shells are generated at higher CVD temperature (> or =900 degrees C). We observed hydrogen uptake of up to 4.5 wt % and 45 g H(2)/L (volumetric density) at -196 degrees C and 20 bar for the carbon materials. The hydrogen uptake was found to be dependent on surface area and was therefore influenced by the choice of zeolite template and carbon source. Zeolite Y-templated N-doped carbons had the highest hydrogen uptake capacity. Gravimetric and volumetric methods gave similar uptake capacity at 1 bar (i.e., 1.6 and 2.0 wt % for zeolite 13X and Y-templated N-doped carbons, respectively). Our findings show that zeolite-templated carbons are attractive for hydrogen storage and highlight the potential benefits of functionalization (nitrogen-doping).
Yang
Zhuxian
Z
School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, U.K.
Xia
Yongde
Y
Sun
Xuezhong
X
Mokaya
Robert
R