Surface‐Modification‐Assisted Construction of Hierarchical Double‐Walled MnO₂ Hollow Nanofibers for High‐Performance Supercapacitor Electrode

Abstract

To achieve effective energy conversion and storage device, a new type of electrode material with stable structure and large surface area is highly desirable. In this paper, a facile route was reported to synthesize hierarchical double-walled MnO 2 hollow nanofibers (MHNFs). Amine-functionalized SiO 2 hollow nanofibers were prepared as a template to adsorb the anionic MnO 4 À . After hydrothermal treatment, NH 2 -SiO 2 @MnO 2 hollow nanofibers were formed. Then by etching SiO 2 with HF, the MHNFs were obtained. The as-synthesized MHNFs were directly used as supercapacitor electrode, which achieved a specific capacitance value of 222.4 F g À 1 , as well as superior cycling capability (94% after 5000 cycles). The MHNFs and activated carborn were employed to assemble an asymmetric supercapacitor (ASC) in 1 M Na 2 SO 4 solution. The device showed the highest energy density of 29.3 W h kg -1 at 90 W kg -1 and the highest power density of 7200 W kg -1 at 7.2 W h kg -1 within the voltage window of 0-1.8 V. These results make the asfabricated MHNFs a suitable electrode material for high efficient electrochemical supercapacitor.[a] W.infiltration. This work suggests the viability and the potential of this efficient approach to design hierarchical MnO 2 electrodes with enhanced supercapacitive properties. Supporting Information SummaryExperimental details, XRD pattern, HRTEM image, TEM image, SEM image FT-IR spectrum and electrochemical analysis (CV and GCD curves) of samples and the comparison of electrochemical performances of MHNFs in this work with literature can be found in the Supporting Information.

Construction of Hierarchical Mn2O3@MnO2 Core–Shell Nanofibers for Enhanced Performance Supercapacitor Electrodes

“…The growth mechanism of Mn 2 O 3 @MnO 2 involves two steps. First, Mn 2 O 3 nanofibers and KMnO 4 act as the reducing and oxidant agents, respectively, and the redox reaction between two reactants occurs under hydrothermal condition, leading to the in situ nucleation of MnO 2 on the surface of the Mn 2 O 3 nanofibers uniformly . With MnO 2 serving as nucleation sites, the interconnected MnO 2 nanosheets are generated with the self-decomposition of KMnO 4 and the redox reaction between the Mn 2 O 3 and KMnO 4 , resulting in the final Mn 2 O 3 @MnO 2 core–shell structure.…”

Construction of Novel Hierarchical Honeycomb-Like Mn3O4 MnO2 Core-Shell Architecture with High Voltage for Advanced Aqueous Zinc-Ion Batteries

“…The formation mechanism of Mn 3 O 4 @MnO 2 composite involves two reaction steps: To start with, the redox reaction between Mn 3 O 4 and KMnO 4 occurs during the hydrothermal process, then the MnO 2 is in situ nucleation onto the surface of Mn 3 O 4 nanoparticles uniformly. 35 Subsequently, with the MnO 2 acting as the nucleation sites, the interconnected MnO 2 nanosheets are further formed via the self-decomposition of KMnO 4 and the redox reaction between Mn 3 O 4 and KMnO 4 , 36,37 resulting in the hierarchical core-shell honeycomb-like Mn 3 O 4 @MnO 2 . Figure 1b shows the FESEM image of Mn 3 O 4 , the Mn 3 O 4 consisting of many nanoparticles with the size of 100 ∼ 200 nm.…”

Fabrication of Three-Dimensional Porous NiO/Amorphous Ni(OH)2 Composites for Supercapacitors

“…8,9 The latter shows higher capacitance and energy density than the former. 10 At present, supercapacitors are extensively used in hybrid electric automobiles, renewable energy systems, and other domains. 11,12 NiO has gained much attention due to easy preparation, low toxicity, excellent theoretical capacitance, and redox reversibility.…”

“…Therefore, several new energy devices have been explored, including fuel cells, secondary batteries, and supercapacitors . Supercapacitors have attracted widespread concern on various advantages, , which are primarily divided into double layer capacitors (EDLC, ion adsorption mechanism in surface) and pseudo-capacitors (PC, redox reaction mechanism in surface) on the basis of charge storage mechanisms. , The latter shows higher capacitance and energy density than the former . At present, supercapacitors are extensively used in hybrid electric automobiles, renewable energy systems, and other domains. , …”