Experimental evaluation of total hydrogen capacity for fullerite C 60

Abstract

The fullerene is the fourth allotropic modification of carbon and its properties, as volume, gravimetric and electrochemical capacities, are in excess of many similar properties of metal hydrides and hydrocarbons. The solution of the problem of the reversible hydrogenation of each carbon atom in the frame of fullerene molecule will allow to create the hydrogen storage with the capacity up to 7.7 wt.% H. A series of experiments have been conducted to evaluate the full hydrogenation of fullerite C 60; hydrofullerenes have been produced experimentally with the variable content of hydrogen. The optimum regime of C 60 hydrogenation has been determined resulting in the full hydrogenation of fullerene molecule C 60. As was apparent after the tests, the sequence of formation of hydrogenated fullerene molecule C 60H 60 in fullerite has been going in the following order: the molecular hydrogen dissolution in octahedral interstices of fcc lattice of fullerite, the dissociation of hydrogen molecules in going from octa- to tetrahedral interstices, the interaction of hydrogen atoms with fullerene molecule. It has been demonstrated that chemisorption process of hydrogen by molecule C 60 is limited by diffusive processes in fullerite after hydrogen concentration conformed to C 60H 36. The spectral analysis have shown that the second stage process of chemisorption follows the compressive shell model. The suggestion of the model of processes going on at the interaction between H 2 and fullerite C 60 has been made. The mechanism for the definition of hydrogenation degree of molecule C 60 has been proposed in the present paper.