Nano “Koosh Balls” of Mesoporous MnO₂: Improved Supercapacitor Performance through Superior Ion Transport

Abstract

Manganese dioxide nanomaterials with "Koosh-ball"-like morphology (MnO -KBs) as well as worm-like nanotubes (MnO -NWs) are obtained by employing Tween 20 as the reducing and structure-directing agent, and KMnO as a MnO precursor. Whereas the MnO -KBs are interconnected through tubular extensions, the MnO -NWs are largely disconnected. Both MnO -KBs and MnO -NWs have large BET surface areas (>200 m g ), and are thermally robust up to 300 °C. Electrochemical studies reveal that the highest specific capacitance (C ) obtained for MnO -KBs (272 F g ) is significantly higher than that of MnO -NWs (129 F g ). The C values correlate well with the electroactive surface areas of the materials: MnO -KBs have a significantly higher electrolyte-accessible surface area. Electrochemical impedance spectroscopy (EIS) reveals a higher electron-transfer rate at the electrode/electrolyte interface for MnO -KBs than for MnO -NWs. The multiple tubular interconnections between individual MnO -KBs allow improved ion penetration and act as conduits for their propagation, shortening the diffusion distances of the ions from external electrolytes to the interior of the MnO framework. Thus, this work exemplifies the importance of interconnections for enhancing the electrochemical performance of nanomaterials employed for energy storage.

Tween 20‐Assisted Synthesis of Uniform Mesoporous Silica Nanospheres with Wormhole Porosity for Efficient Intracellular Curcumin Delivery

“…Utilizing these unique features of non‐ionic surfactants, Prouzet and coworkers reported synthesis of mesoporous silica materials using PEO and Tween surfactants as structure‐directing agents, albeit without any definite demonstration of size‐ and shape‐control of the resulting materials . We have recently shown the synthesis of uniform spheroidal nanoassemblies of magnetite and mesoporous nano “Koosh balls” of MnO 2 using Tween surfactants as structure‐directing agents ,. In this work, we have extended the utility of Tween 20 for mesoporous nanomaterial synthesis by preparing uniform MSNs with wormhole‐like framework‐confined porosity.…”

Importance of Electrode Preparation Methodologies in Supercapacitor Applications

“…On the other hand, in the cases of PTFE and Nafion, phase angles slightly decrease after reaching a maximum value in the low-frequency region which could be due to the dissolution of the electrolyte ions or the unfavorable diffusion of ions (Figure 7d). 13 This observation is also reflected by a decrease in R des for Nafion and PTFE presumably due to the fact that lesser number of ions were adsorbed at the porous interface as the resistance for the desorption of ions was lowered (Table 4). As a consequence, the capacitance values also declined for PTFE and Nafion (Table 3).…”

Supercapacitive performance of C-axis preferentially oriented TiO2 nanotube arrays decorated with MnO2 nanoparticles

“…So there were two effective methods to increase performance: (1) MnO 2 nanoparticles were synthesized to increase the surface area, while adding a thin layer in electrochemical reactive redox process. (2) Conductive materials were used to improve electrical conductivity [9].…”