Urea-treatment of CoOx carbon nanofibers to improve the electrochemical performance of supercapacitor using aqueous electrolytes

• Published in: Journal of materials science & technology Vol. 200; pp. 83 - 92
• Main Authors: Joshi, Bhavana, Kim, Seongdong, Samuel, Edmund, Huh, Jungwoo, Almoiqli, Mohammed S., Alharbi, Khalid N., Yoon, Sam S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20.11.2024
• Subjects: Carbon nanofiber; Electrospinning; Flexible supercapacitor; Freestanding electrode; Urea; ZIF-67; Carbon nanofiber; Electrospinning; Urea; Flexible supercapacitor; Freestanding electrode; ZIF-67
• ISSN: 1005-0302
• DOI: 10.1016/j.jmst.2024.02.063

•A urea-treated CoOx/CNF freestanding electrode, capable of subduing faradaic currents, was proposed.•Urea treatment enhanced the electrical and ionic conductivities of the CoOx/CNF freestanding electrode.•The urea-treated CoOx/CNF electrode retained 91 % of capacitance after 10,000 GCD cycles.•Urea-induced heteroatoms promoted charge redistribution, achieving an energy density of 61 µWh cm–2. Supercapacitors (SCs) play a crucial role in flexible electronics, necessitating innovative approaches to enhance surface faradaic reactions and minimize faradaic diffusion while using aqueous electrolytes. Thus, the urea treatment of cobalt oxide (CoOx)-decorated carbon nanofibers (CNFs) is proposed in this study to decrease the contribution of faradaic diffusion-limited current. Flexible CoOx/CNF electrodes were obtained by annealing ZIF-67-grafted polyacrylonitrile (PAN) fibers via a wet chemical method. The urea treatment of CoOx/CNFs increased the content of sp2-hybridized carbon and pyridinic nitrogen, as confirmed by X-ray photoelectron spectroscopy, effectively enhancing conductivity and pseudocapacitive charge storage capability via nitrogen doping. Notably, urea-treated CoOx/CNF electrode samples exhibited a capacitance of 750 mF cm−2 at a scan rate of 10 mV s−1, while retaining more than 81 % capacitance at a higher scan rate of 100 mV s-1. The cyclic voltammetry curves during variable bending angle testing (0°, 45°, and 90°) exhibited negligible changes, indicating the excellent flexibility of the SCs. The CoOx/CNFs and urea-treated CoOx/CNFs exhibited 80 % and 91 % capacitance retentions, respectively, after 10,000 galvanostatic charge and discharge cycles. Furthermore, the attained energy densities of 76 and 61 µWh cm−2 at the respective power densities of 2 and 20 mW cm−2 indicated the excellent electrochemical performance of the optimal urea-treated CoOx/CNF electrode. [Display omitted]