Hydrogen Adsorption\nand Isotope Mixing on Copper-Functionalized\nActivated Carbons

Abstract

High-specific surface area (SSA)\ncarbons were functionalized with\ncopper nanoclusters and evaluated as potential hydrogen storage materials.\nThe adsorption and desorption behaviors of the copper-functionalized\nmaterial and pristine high-SSA carbon are compared between 77 and\n400 K using adsorption isotherms up to 10 MPa and by temperature-programmed\ndesorption of isotopic hydrogen. The high-SSA activated carbon with\ncopper nanoclusters exhibited two desorption behaviors. (1) A desorption\npeak at 120 K, which was associated with physisorption on carbon,\nand (2) a desorption peak at 310 K, which was associated with a chemisorption\nprocess involving copper. The desorption from copper was strongly\ndependent on the hydrogen pressure used for loading, and dissociation\nof the hydrogen could be avoided by loading at low temperature and\npressure. An enhancement of hydrogen uptake in the low-coverage (Henry’s\nlaw) regime at ambient temperatures with copper nanoclusters was observed,\ndemonstrating an increased adsorption enthalpy with the copper-modified\nmaterial. Binding site energies of 6 and 20 kJ/mol for H₂ physisorption and H chemisorption, respectively, were obtained from\nfits to isotherms.