Laser Carbonization of PAN-Nanofiber Mats with Enhanced Surface Area and Porosity

Abstract

Here we present a novel laser process to generate carbon nanofiber nonwovens from polyacrylonitrile. We produce carbon nanofabrics via electrospinning followed by infrared laser-induced carbonization, facilitating high surface area and well-controlled hierarchical porosity. The process allows precise control of the carbonization conditions and provides high nanoscale porosity. In comparison with classical thermal carbonization, the laser process produces much higher surface areas and smaller pores. Furthermore, we investigate the carbonization performance and the morphology of polyacrylonitrile nanofibers compounded with graphene nanoplatelet fillers.

Electrochemical characterization of laser‐carbonized polyacrylonitrile nanofiber nonwovens

“…PAN‐based carbon‐fiber precursors were obtained by the electrospinning of solutions of poly(acrylonitrile‐ co ‐itaconic acid) in dimethylformamide, as described previously . The itaconic acid comonomer facilitated lower cyclization temperatures during the stabilization step .…”

“…We then stabilized the fiber mats at a temperature of 250 °C in air (see Supporting Information for the detailed protocol). Furthermore, this multistep heating protocol has been shown to ease the formation of a three‐dimensional fiber network and increase the carbon yield . In the final carbonization step, we performed a fast h ν at a heating rate of 50 K/s under nitrogen (Oxygen < 20 ppm) for 60 s to convert the thermally stabilized PAN into graphitic carbon .…”

“…PAN-based carbon-fiber precursors were obtained by the electrospinning of solutions of poly(acrylonitrile-co-itaconic acid) in dimethylformamide, as described previously. 15 The itaconic acid comonomer facilitated lower cyclization temperatures during the stabilization step. 19 We first heated the fiber fleece for 2 h at 100 8C to drive out the residual solvent and reduced material shrinkage in the subsequent processing steps.…”

“…[10][11][12][13][14] We recently reported a method where thermally stabilized PAN fibers are carbonized with IR laser radiation instead of high temperatures. 15 This process allows for a more localized carbonization because of hm and reduced-temperature gradients as the laser beam can be scanned over the sample. Furthermore, hm carbonization is fast, and full conversion can be obtained within a few seconds.…”

“…[16][17][18] So far, fibers that have been converted with the aforementioned alternative carbonization methods have been investigated with respect to their surface properties. 10,15 However, there is little information on how far carbonization affects the electrochemical properties of carbon fibers. It is of interest to know whether carbon fibers derived from alternative carbonization processes exhibit superior electronic properties over D-carbonized materials.…”