Pseudocapacitive Contributions to Charge Storage in Highly Ordered Mesoporous Group V Transition Metal Oxides with Iso-Oriented Layered Nanocrystalline Domains

Abstract

Amphiphilic block copolymers are very attractive as templates to produce inorganic architectures with nanoscale periodicity because of their ability to form soft superstructures and to interact with inorganic materials. In this paper, we report the synthesis and electrochemical properties of highly ordered mesoporous T-Nb(2)O(5), L-Ta(2)O(5), and TaNbO(5) solid solution thin films with iso-oriented layered nanocrystalline domains. These oxide materials were fabricated by coassembly of inorganic sol-gel reagents with a poly(ethylene-co-butylene)-b-poly(ethylene oxide) diblock copolymer, referred to as KLE. We establish that all materials employed here are highly crystalline and have an ordered cubic pore-solid architecture after thermal treatment. We also demonstrate that these group V transition metal oxides can be readily produced with a high degree of crystallographic alignment on virtually any substrate in contrast to classical solution-phase epitaxy which requires the use of a single-crystalline substrate to achieve oriented crystal growth. Moreover, we show the benefits of producing a material with both a mesoporous morphology and crystallographically oriented domains. Mesoporous T-Nb(2)O(5) films exhibit high levels of pseudocapacitive charge storage and much higher capacities than mesoporous amorphous films of the same initial Nb(2)O(5) composition. Part of this high capacity stems from very facile intercalation pseudocapacitance. This process occurs at rates comparable to traditional redox pseudocapacitance in high surface area Nb(2)O(5) because of the periodic nanoscale porosity, the iso-orientation of the layered nanocrystalline pore walls, and the mechanical flexibility of periodic porous materials.

Electrochemical Energy Storage Applications of CVD Grown Niobium Oxide Thin Films

“…37 However, prior research does not indicate whether one particular phase of Nb2O5 is better than another. While the pseudohexagonal phase of Nb2O5 (TT-Nb2O5) is preferred in electrochromic applications, the tetragonal phase (MNb2O5) has shown the best performance when integrated in the electrode materials for lithium ion batteries.…”

Electrochemical Transport Phenomena in Hybrid Pseudocapacitors under Galvanostatic Cycling

“…It is interesting to note that the synthesis of Nb 2 O 5 described in Ref. 13 resulted in Nb 2 O 5 electrodes with no initial Li and minimal contaminants, based on X-ray photoelectron spectroscopy data. 13 Pseudocapacitance has also been demonstrated with MnO 2 involved in reversible redox reactions with H + , K + , and Li + .…”

Synthesis of porous NiO nanocrystals with controllable surface area and their application as supercapacitor electrodes

“…It has been shown that the electrochemical performance of NiO nanocrystals largely depends on its microstructure, surface area, and the presence of dopants [30][31][32][33][34][35], suggesting that the development of controlled syntheses of NiO nanostructures with the desired features, e.g., high electronic conductivity, low diffusion resistance to protons/cations, and high electroactive area is of paramount importance. Although several other techniques-such as surfactanttemplate [36], sol-gel [37][38][39], anodization [40], and hard template [41][42][43] methods-have been reported for synthesizing porous nanocrystals, solvothermal/ hydrothermal techniques [3,30] are of particular interest as they are flexible and can be readily adapted to large scale production. Herein, we report a facile way to synthesize porous NiO nanoslices, nanoplates, and nanocolumns with adjustable surface area, and that these NiO nanostructures show a structure-dependent specific charge capacitance.…”