Thermodynamic properties and hydrogen accumulation ability of fullerene hydride C60H36

Abstract

Thermodynamic properties of fullerene hydride C60H36 in the ideal- gas and crystal states were studied by theoretical methods. Molecular structures and vibration frequencies were calculated for 9 isomers of C60H36 by the density functional theory ( DFT) by use of a combination of the B3LYP functional with 6-31G* basis sets. Ideal- gas thermodynamic properties were calculated based on those parameters. Enthalpies of formation of C60H36 isomers in the ideal- gas state were derived from homodesmic reactions involving adamantane, cyclohexane, and C-60 fullerene. Using the standard methods of statistical mechanics, heat capacity and derived thermodynamic properties of crystalline C60H36 were calculated at 340 1000 K that extended the range of experimental measurements. With a crystal-gas heat capacity difference, the experimental value of sublimation enthalpy was extrapolated to room temperature as Delta H-sub(m)o ( 298.15 K) = ( 193 +/- 10) kJ.mol(-1). Combining this value with the known experimental enthalpy of formation in the crystalline state, the ideal- gas enthalpy of formation of C60H36 at the synthesized sample isomer composition was obtained: Delta(f) H-m(o) (298.15 K) ( 1206 +/- 28) kJ. mol(-1). Equilibrium constants and compositions were calculated for the reactions of hydrogenation of C-60 fullerene in different states. It was shown that C-60 can act as a hydrogen accumulator.