Carbon nanotubule membranes for electrochemical energy storage and production

Ensembles of aligned and monodisperse tubules of graphitic carbon can be prepared by a templating method(1-4) that involves the chemical-vapour deposition of carbon within the pores of alumina membranes(5-7). Tubules with diameters as small as 20 nm have been prepared in this way(7,8). The carbon comprising these tubules can be transformed from a disordered material to very highly ordered graphite(5). Here we show that template-synthesized carbon tubules can be fabricated as free-standing nanoporous carbon membranes, and that narrower, highly ordered graphitic carbon nanotubes can be prepared within the membrane's tubules. Both the outer and the inner tubules are electrochemically active for intercalation of lithium ions, suggesting possible applications in lithium-ion batteries(9,10). The membranes can also be filled with nanoparticles of electrocatalytic metals and alloys. Such catalyst-loaded membranes can be used to electrocatalyse O-2 reduction and methanol oxidation, two reactions of importance to fuel-cell technology.