Fabrication and characteristics of sulfonated carbon foam via high internal phase emulsions with polypyrrole-modified carbon nanotubes

Abstract

Highly conductive carbon foam with a high specific surface area was fabricated using a microporous polymer foam template with an open-cell structure. The cell size, specific surface area, electrical conductivity, and compressive properties of the foam were controlled by the polymerization, sulfonation, and carbonization of a carbon nanotube (CNT)-based high internal phase emulsion. The CNT surface was modified using polypyrrole (PPy), a conductive polymer, to increase the affinity of the CNT toward the oil phase in the high internal phase emulsion and to improve the electrical conductivity of the microporous foam after polymerization. An increase in the PPy-CNT content reduced the cell size and increased the electrical conductivity of the foam. The electrical conductivity and thermal stability of the foam were significantly improved through sulfonation. The cell morphology of the foam was maintained even after high-temperature carbonization due to its densely crosslinked structure with thioether bridges. The sulfonation of the polymer foam with PPy-CNT 1 wt%, followed by carbonization at 1000 °C, resulted in the formation of sulfonated carbon foam, which exhibited a smaller cell size (∼2 μm) and improved electrical conductivity (∼102 S/m), crush strength (∼4 MPa), and thermal stability (∼90% remaining) compared to microporous polymer foams. However, the specific surface area (∼500 m2/g) of the sulfonated carbon foam carbonized at 800 °C was significantly higher than that of the sulfonated carbon foam carbonized at 1000 °C.