(631e) Controlling Micro- and Meso- Scaled Pores In Carbon Nanofibers From Immiscible Polymers For Energy Applications

Nanofibers were electrospun from blend solutions of polyacrylonitrile (PAN) and various sacrificial polymers including cellulose diacetate (CDA). The nanofibers were stabilized in air and carbonized in nitrogen to produce micro- and meso- porous nanofibers.  The heat treatment converted PAN, a common precursor for carbon fibers, to pure carbon but pyrolyzed the sacrificial polymer to create pores within the nanofiber. Similar to other works, the rapid evaporation of solvent during electrospinning is thought to kinetically trap immiscible polymers in small domains during phase separation caused by evaporating the solvent. In the current study, the electrospinning conditions including temperature, blend ratio, molecular weight, and the presence of a co-solvent were varied to control the pore diameter distribution after carbonization. By varying these conditions, the average pore diameter was varied from 3.4 to 15.6 nm and maintained at least 66 m²/g of BET surface area. The pore distribution was controlled in a single modal pore distribution as well as in a bimodal distribution. CDA was selectively removed from the uncarbonized nanofibers to further investigate the porous nature of the nanofibers. Nitrogen physisorption and TEM images were used to measure and confirm the pore distributions and surface area. The carbon nanofibers were then tested for their performance as a stand-alone supercapacitor electrode and as a Li-Air cathode which have been reported to have different pore distribution requirements for optimal performance.