Thermoelectric study of hydrogen storage in carbon nanotubes

In situ resistivity and thermoelectric power (S) have been used to study the nature of the adsorption of hydrogen in bundles of single-walled carbon nanotubes for H₂ pressure P <1 atm and temperatures 77 K <T<500 K. Isothermal plots of S vs. Δρ/ρ₀ are found to exhibit linear behavior as a function of gas coverage, consistent with a physisorption process. Studies of S, ρ at T = 500 K as a function of pressure exhibit a plateau at a pressure P∼40 Torr, the same pressure where the H % measurements suggest the highest binding energy sites are being saturated. The effects of H₂ exposure at 500 K on the thermoelectric transport properties are fully reversible.