Introducing carbonized electrospun pan nanofibers as flow battery electrodes
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The objective of this thesis was to develop an electrospun polyacrylonitrile (PAN)-based nanofiber that has unique properties as an electrode material. Stabilizing, carbonizing, and chemical activation of these nanofibers can help to improve meso-porous carbon for the application as carbon-based electrodes. The study includes two main parts. In part I, nanofibers were electrospun under different electrospinning conditions, such as applied voltage and the distance between the spinneret and the target, to determine the best process conditions. Then, the PAN nanofibrous mats were stabilized in air, carbonized in inert atmosphere (argon), and activated using a potassium hydroxide (KOH) chemical method. During the chemical activation, carbonized nanofibers were immersed in an aqueous KOH solution. In part II, the structure and morphology were studied using scanning electron microscopy (SEM). The diameter of the nanofibers was measured and monitored as a function of the applied voltage, distance between the spinneret and the target, and the chemical (KOH) treatment. Porosity of carbon-based nanofibers has been studied by weighing the nanofibrous mat after absorption of isopropanol. Porosity by chemical treatment improved from 60% to 90%, thus providing a higher contact area, which is an important factor for electrodes. As a result of the physical and chemical treatments, wettability of the electrospun nanofibers varied from hydrophobicity with a contact angle of 150° to superhydrophilicity with a contact angle of 20°. The electrochemical performance of the electrodes was tested by cyclic voltammetry (CV) in a hydrochloric acid (HCl) aqueous solution in the presence of an Fe(III)/(II) redox couple. Results showed that the prepared sample has a smaller ∆Ep unlike the carbon felt, which is an indicator of a more active PAN carbonized nanofiber in comparison to the felt. Carbon nanofiber (CNF) samples have a higher peak current, which indicates a higher surface area.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering