Abstract
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 pWh 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.
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