Binder‐Free Synthesis of Mesoporous Nickel Tungstate for Aqueous Asymmetric Supercapacitor Applications: Effect of Film Thickness

Abstract

However, the cost and the energy stored by these devices vary with the design, chemistry, and materials used to fabricate. The specific energy for batteries is comparatively more than the SCs and capacitors. [1,2] Due to outstanding cycle stability, greater power density, and rapid charge-discharge rate, SCs are some of the better optimistic contenders. [3,4] A significant drawback of SCs is that they are deficient in specific energy to fulfill the growing energy requirements for new-age energy storage equipment. [5,6] Nowadays, more research activities have been concentrated to enhance the specific energy of SCs without losing their specific power and cyclability. [7,8] The specific energy (E ¼ 0.5CV 2 ) can be raised by improving capacitance (C) and operating potential window (V ). Different electroactive materials with rages of capacitance values have been used to fabricate SCs. [9][10][11] Hence, the preparation of novel electrode materials possessing high specific capacitance and fabrication of asymmetric supercapacitors (ASCs) to overcome the issue of low cell potential can result in enhanced specific energy. [12,13] Metal tungstates have the general formula AWO 4 , where A is a divalent cation (A 2þ ¼ Ni, Fe, Mn, Cu, Co) that acts as a network modifier. The monoclinic crystal structure of metal tungstates (shown in Figure 1a,b) resembles with the crystal structure of metal sulfates. [14] Crystal structure formed by tungstate ion with bivalent metal ion forms tetrahedral coordination. However, due to the smaller radius of bivalent cations like nickel having ionic radius of less than 0.77 Å will perform well for the supercapacitors. In addition to this, the bimetallic nature of the metal tungstates helps to improve the energy storage capacity of materials compared to a single metal compound like NiO and WO 3 . Compared to nickel oxide and hydroxide, NiWO 4 have higher molecular mass, leading to lower theoretical capacitance. Higher cost of preparation due to addition of W in synthesis process can be considered a disadvantage. Metal oxides, including tungsten oxide and metal tungstates, show several advantages over other materials, such as low toxicity, low synthetic cost, high resistance against photocorrosion, and compatibility with up-scale. Normally, metal tungstate materials were tested for SC applications, [15] Li-ion battery, [16] electrocatalysis, [17] gas

Facile Synthesis and Characterization of Novel Carbon Nanofiber-Doped MWO4 (M–Mn, Co, Ni, Mn–Co, Mn–Ni, Ni–Co)-Based Nanostructured Electrode Materials for Application in Electrochemical Supercapacitors and Photoelectrochemical Water Splitting

“…In the high-resolution X-PS spectra of Mn 2p, the binding energies are located at 641.6 and 653.45 eV, which are ascribed to Mn 2p 3/2 and Mn 2p 1/2 , respectively (Figure b), which represent the Mn 2+ state . In the deconvoluted X-PS spectra of Ni 2p shown in Figure c, the Ni 2p two peaks are centered at 855.7 and 873.4 eV, which are attributed to Ni 2p 3/2 and Ni 2p 1/2 , respectively, indicative of the Ni 2+ state. In W 4f spectra (Figure d), the binding energies at 35.2 and 37.4 eV with peak separation of 2.2 eV correspond to W 4f 7/2 and W 4f 5/2 levels of tungsten atoms for the W 6+ state of oxide, respectively.…”

“…7 and 873.4 eV, which are attributed to Ni 2p 3/2 and Ni 2p 1/2 , respectively,52 indicative of the Ni 2+ state. In W 4f spectra (Figure7d), the binding energies at 35.2 and 37.4 eV with peak separation of 2.2 eV correspond to W 4f 7/2 and W 4f 5/2 levels of tungsten atoms for the W 6+ state of oxide, respectively.…”

Efficient Electrochemical Water Splitting Through Self‐Supported Copper Selenide Nanosheets on Cu Foil: Effect of Immersion Time

“…The broad absorption band ( ν 6 ) from –OH stretching vibrations of the absorbed water molecules is observed at around 3115–3550 cm −1 . [ 26 ] The absorptions ( ν 4 and ν 5 ) from bending vibrations of ‐OH bond observed at wavenumbers of 1595 and 1631 cm −1 correspond to structural and adsorbed hydroxyl groups, respectively. Furthermore, absorption bands ( ν 2 and ν 3 ) at wavenumbers of 1357 and 1384 cm −1 correspond to the asymmetric stretching of Cu–OH and Cu–Se bonding, respectively.…”

Fabrication of MnCoS Thin Films Deposited by the SILAR Method with the Assistance of Surfactants and Supercapacitor Properties

“…It does not require a vacuum system, complex equipment, or adhesives. A dense thin film of active materials is vital for the electrochemical performance of a supercapacitor, and the deposition of a dense thin film using the SILAR method on a substrate without a binder is still challenging due to the small surface area and poor wettability of the substrate's surface [28][29][30][31][32][33][34][35][36].…”