Hydrogen adsorption on Pd- and Ru-doped C₆₀ fullerene at an ambient temperature

Palladium- and ruthenium-doped C₆₀ fullerene compounds were synthesized by incipient wetness impregnation of C₆₀ fullerene with the corresponding metal acetylacetonate precursors. Transmission electron microscopy (TEM) imaging of the metal-doped C₆₀ fullerene samples showed different dispersion morphologies of palladium and ruthenium particles on the C₆₀ matrix. Raman spectra revealed a drastic decrease in peak intensity followed by disappearance of several bands indicating the distortion of the C₆₀ cage structure. The amorphous nature of the C₆₀ fullerene compounds was confirmed by the X-ray diffraction study. Hydrogen adsorption amount of 0.85 wt % and 0. 69 wt % on Pd-C₆₀ and Ru-C ₆₀, respectively, as compared to 0.3 wt % on the pure C₆₀ fullerene were measured at 300 bar and 298 K. The enhancement in the hydrogen uptakes can be attributed to several factors, including adsorption of molecular H₂ on the defect sites, metallic hydride formation, spillover of hydrogen, and bond formation with atomic hydrogen with different active sites of carbon of host fullerene. The hydrogen adsorption isotherms are of type III and can be correlated by the Freundlich (for Ru-C₆₀) and modified Oswin equations (for Pd-C₆₀ and pristine C₆₀).