Preparation of porous carbon by defluorination of poly(tetrafluoroethylene) and the effect of γ-irradiation on the polymer

Porous carbon materials were prepared by direct reduction of poly(tetrafluoroethylene) (PTFE) powder with potassium vapor. After the reaction, the black powder product under vacuum showed a Raman peak at around 1950 cm(-1), which was assigned to the C dropC bond in a polyyne-type structure. After the byproduct, potassium fluoride, was removed, by using hydrogen fluoride, the powder was heat-treated up to 2800 degreesC in an argon atmosphere. The structural changes of the powder with heat treatment were analyzed by Raman spectroscopy. The changes in the pore structure were examined by N-2 adsorption. It was found that the product contains a high amount of mesopores as well as micropores. For example, the meso- and micropore volumes for the carbon heat-treated at 1000 degreesC were 669-844 and 200-233 mm(3)/g, respectively. The same experiments were performed by using gamma -irradiated PTFE powder. The product gave a more porous structure, i.e., a higher total surface area of 1385-1516 m(2)/g and mesopore area of 877-1126 m(2)/g, while the carbon derived from the nonirradiated polymer showed 1041 and 620 m(2)/g, respectively. The formation mechanism of the porous carbons is discussed on the basis of the polymer aggregation, and the effects of defluorination and gamma -irradiation on the polymer.