Synthesis and Characterization of Novel Hierarchically Functionalized Carbon Nanofibers for Energy Conversion and Storage Applications

Abstract

Among various energy conversion and storage devices available in the market, supercapacitors are deemed as an effective, competitive solution to the increasing demand for high-power density energy-storage devices. Yet, supercapacitors usually carry relatively low energy density compared to batteries. Nanostructured electrode materials are expected being able to greatly enhance the electrochemical performance of supercapacitors. This research aims at rational synthesis and electrochemical characterization of novel hierarchically functionalized carbon nanofibers (CNFs) for use as advanced electrode materials of supercapacitors. These novel CNFs [(i.e., graphene-beaded CNFs (G/CNFs) and carbon nanotube (CNT)-grown CNFs (CNT/CNFs)] were successfully synthesized. The unique synthesis routes consist of electrospinning the precursor polymer nanofibers, followed by controlled carbonization, chemical vapor deposition (CVD) for CNT growth, and in situ polymerization for coating nanostructured conducting polymer. These new electrode materials carry the advantages of G/CNFs and CNT/CNFs (e.g., unique nanostructural continuity, large specific surface area, low intrinsic contact electric resistance, etc.) and conducting polymers (e.g., high pseudocapacitance), and therefore show excellent electrochemical performance including high specific capacitance, superior energy and power densities, and excellent cyclability. In addition, this work also provides the experimental study on parameter dependency of conic angle in electrospinning and scalable fabrication of core-shell nanofibers via needleless emulsion electrospinning.