J. Phys. IVFrance 12 (2002) 0 EDP Sciences, Les Ulis DOI: 10.1051/3p420020087 Pr4- 129 Hydrogen storage in carbon nanotubes produced by CVD A. Fonseca, N. Pierard, S. Tollis, G. Bister’, Z. Konya’, N. Nagaraju and J.B. Nagy Laboratoire de Rksonance Magnktique Nuckaire, Facult& Universitalres Notre Dame de la Paix, 67 rue de Bruxelles, 5000 Namur, Belgium ’ Deparfment of Applied and Environmental Chemistry, University of Szeged, Rerrich Bela ter I, 6720 Szeged, Hungary Abstract. Smgle- and multi-wall carbon nanotubes syntheslzed by catalytic decomposltlon of methane and acetylene, respechvely were studled for theu hydrogen adsorption capacity m their hollow and on their outer surface The hydrogen storage capacity of the samples was measured for pressures O-9 bar at 295 K and at 77 K The results at chfferent temperatures on the crude sample (closed tubes lo-50 pm long), on the purified sample (open tubes lo-50 pm long) and on the purlfed and broken sample (open tubes 0.1-O 7 pm long) show that breakmg the nanotubes allows one to adsorb hydrogen m theu hollow In ad&Ion, the relative amounts of hydrogen adsorbed m the hollow and outer parts of the nanotubes can be dlstmgmshed 1. INTRODUCTION Today the environmental concerns and the decreasmg resources of fossil fuels are exerting pressure to develop cleaner fuels and more efficient processes. Accordmg to the US Department of Energy’s Hydrogen Program for the 2 1” century (DOE Program [l]), hydrogen will definitively become the unique, safe and clean energy of the future. The US automobile mdustry 1s expected to produce commercial busses by 2002 and tens of thousands of cars annually by 2004, that ~111 utilise the PEM fuel cell as the on board hydrogen power system [2] The energy converslon capacity of the actual PEM fuel cells is 1 kW h/60 g of Hz At present, the hydrogen tank is the major problem. Some solutions have been already proposed (Table 1) but all have some disadvantage (pollution, cost, weight,. . ) [3-91. Table 1. Hz storage capacltles of some efticlent fuel reservoirs Hydrogen Temperature source 6) Pressure Hydrogen stored Reference (bar) H2 (hqmd) 20 HI (pressured) 298 CH4 1073 CH,OH 298 MgHz 493 NaBH4 298 ’ SWNTs EO(298) 1 330(750) 1 1 1 1 120 (wt. %) 50 25 5-6 10 8 8 3 (4 2) (kg/l 00 1) 70 2 O(3 4) [31 [31 [41 (51 [3, 61 [71 tk91 The best fuel for the PEM fuel cell 1s pressunsed H2 but Its Hz storage capacity is far below the “DOE Hydrogen Plan” limits (ca 6.5 wt. % or 6.3 kg/100 I) [l]. Llquld hydrogen overcomes the DOE hmlt but its coohng IS too expensive. The higher Hz storage capacities are found for hydrocarbons and for alcohols (Table 1) but the on board production of Hz from carbon contammg fuels IS achieved by a reforming process that generates CO1 that IS not environmentally friendly. In the second position are the hydndes but again, they suffer