Abstract
MnO2-deposited lignin-based carbon fiber (MnO2-LCF) mats are fabricated for supercapacitor applications. LCF mats are produced from alkali lignin via electrospinning followed by stabilization and carbonization. The carbonization process is carried out at 800, 900, and 1000 °C, and the corresponding mats are denoted as MnO2-LCF-800, MnO2-LCF-900, and MnO2-LCF-1000, respectively. The LCF mats are immersed in a KMnO4 solution at room temperature for 72 h to obtain MnO2-LCF mats. The scanning electron microscopy and X-ray diffraction analysis confirm the deposition of MnO2 on the LCFs. The Brunauer–Emmett–Teller analysis, X-ray spectroscopy, and Raman spectroscopy reveal that MnO2-LCF-800 mat possesses a large number of mesopores and Mn vacancies as compared to MnO2-LCF-900 mat and MnO2-LCF-1000 mat. Consequently, MnO2-LCF-800 mat possesses the best electrochemical properties with a specific capacitance of 131.28 F∙g−1, an energy density of 14.77 Wh∙kg−1, and a power density of 135.01 W∙kg−1 at a specific current of 0.3 A∙g−1. Hence, MnO2-LCF-800 mat shows high potential to be used as a high-performance supercapacitor.
Highlights
With the rapid depletion of energy and the deterioration of the environment, the development of the energy conversion and energy storage technologies has become imperative
The mass loading of MnO2 in lignin-based carbon fibers (LCFs) mats were calculated using the following equations: M = (m2 − m1)/s where M is the mass loading of MnO2 in LCF mats, m1 is the mass of LCF mats before reaction, m2 is the mass of LCF mats after reaction, s is the area of mats(cm2)
Nano MnO2 flakes radially grown on LCF to obtain MnO2-LCF mats, which can be used as freestanding binder-free supercapacitor electrodes
Summary
With the rapid depletion of energy and the deterioration of the environment, the development of the energy conversion and energy storage technologies has become imperative. Compared to double-layer capacitors, pseudocapacitors show high energy and power densities This is because fast and reversible redox reactions occur at or near the electrode surface of pseudocapacitors [9]. Pseudocapacitive charge storage in MnO2 occurs through the redox reaction of Mn (+4 and +3 oxidation states) at the surface. Hong et al [20] fabricated a MnO2-anchored carbon fiber cloth composite through a simple hydrothermal reaction and used it as a supercapacitor electrode. The composite electrode showed a high specific capacitance of 194 mF·cm−2 at a charge-discharge current density of 2 mA·cm−2 and a high energy density of 0.108 mW·cm−2 at a power density of 2 mW·cm−2. The MnO2/carbon fiber composite showed excellent specific capacitance, energy density, and power density at a specific current. The MnO2-loaded LCF composites showed great potential to be used as supercapacitor electrodes
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