Highly porous electrospun polyvinylidene fluoride (PVDF)-based carbon fiber

Abstract

Porous poly(vinylidene fluoride) fibers were prepared by electrospinning from solutions in dimethylformamide, poly(ethylene oxide) (PEO) and water. The PVDF fiber mats were then converted into electrospun carbon fiber paper using a low temperature chemical stabilization treatment (“dehydrofluorination”) followed by carbonization at 1000 °C. The resulting self-supporting carbon fiber paper exhibits unusually high surface area, in excess of 380 m 2/g as measured by the nitrogen adsorption method, and a hierarchical pore structure. The largest pores are formed by the interstices between fibers; intermediate-sized pores arise from liquid–liquid phase separation during electrospinning to form polymer-rich and solvent-rich domains within the fibers; the smallest pores form upon decomposition of the PEO during carbonization. The electrospun carbon paper performs well as an electrode for driving the redox chemistry of ferrocene/ferrocenium. This is attributed to the high surface area of the electrode and the ease of diffusion of the redox-active species within the porous structure. The ratio of the dehydrofluorination agent (1,8-diazabicyclo[5.4.0]undec-7-ene) to vinylidene fluoride during dehydrofluorination was found to be the key to retaining the as-spun pore morphology during carbonization. The structure and morphology were further characterized by Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray diffraction, and Raman spectroscopy.