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⋮C 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 °C 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 °C were 669−844 and 200−233 mm 3 /g, respectively. The same experiments were performed by using γ-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 γ-irradiation on the polymer.