Hydrogen adsorption properties of activated carbons with modified surfaces

摘要

The hydrogen adsorption isotherms of activated carbon fibers loaded with platinum (Pt-ACF) and palladium (Pd-ACF) were accurately measured at ambient temperature over the hydrogen pressure range 0-3.5 MPa by using a high-pressure adsorption apparatus. The amounts of hydrogen adsorbed on the Pt-ACF and Pd-ACF samples were larger than the amount adsorbed on the unmodified ACF sample. Detailed measurement of the hydrogen adsorption isotherms of Pt-ACF and Pd-ACF at a hydrogen pressure up to 0.1 MPa indicated that the increase in adsorption was due to chemisorption of hydrogen on the metal. The hydrogen adsorption properties of ACF oxidized with (NH_4)S2_O_8 or reduced in a hydrogen flow at 1073 K were evaluated at 77 and 303 K over the hydrogen pressure range 0-3.5 MPa. The amount of adsorbed hydrogen was decreased by oxidation and increased by reduction. This result is attributable to a change in the pore structure: that is, oxygen functional groups introduced on the carbon surface inhibited hydrogen adsorption into the micropore with an optimum pore diameter.