Sedgelike Porous Co₃O₄ Nanoarrays as a Novel Positive Electrode Material for Co₃O₄ || Bi₂O₃ Asymmetric Supercapacitors

Abstract

Tuning crystallinity and surface functionality are supreme for extracting maximum charge storage efficiency from electrode materials for energy storage devices. Contextually, suitable organic additives with sluggish precipitants are known to significantly regulate the kinetics of reactions and dimensionality of crystals leading to structures with tuned crystallinity and surface functionality. Accordingly, herein, extremely uniform sedgelike highly porous Co3O4 nanoarrays were synthesized by homogeneous precipitation method using sodium dodecyl sulfate as the organic additive and urea as the sluggish precipitant, under hydrothermal condition. The distinctive physicochemical properties of Co3O4 were identified by powder X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer–Emmett−Teller surface area, and UV–vis diffuse reflectance spectroscopy analyses, which show ∼2 nm crystallinity, uniform sedgelike structure, presence of model micro- and mesopores, and signatures of quantum confinement. Thorough electrochemical studies show that the Co3O4 nanoarrays sample possess lower electrochemical series resistance of 0.4 Ω, and it offers a very high rate-specific capacitance of 2510 F g–1 at an applied current density of 4 A g–1, and retains ∼42% of capacitance at eightfold higher applied current density, when measured in a three-electrode assembly. The sedgelike Co3O4 was used as a positive electrode material, and its compatibility was assessed with microbelt-like two-dimensional (2D) Bi2O3 as the negative electrode material, in a redox ensuing Co3O4 || Bi2O3 asymmetric supercapacitor (ASC) device with a wide operating potential window of 1.4 V. The ASC device offers very high areal and mass-specific capacitance of 479 mF cm–2 & 71 F g–1, respectively, at an applied current density of 6 mA cm–2 and exhibits an excellent rate capacitance of ∼50% at an extremely high current density of 48 mA cm–2. The ASC device also retains ∼95% of the areal capacitance after 5000 galvanostatic charge–discharge cycles at an applied current density of 10 mA cm–2. The Co3O4 || Bi2O3 ASC device also offers high energy density of ∼38.5 Wh kg–1 at a power density of ∼1225 W kg–1 and retains ∼47% of the energy density at a very high power density of ∼9473 W kg–1. Factually, the present study manifests that ideal porosity and surface properties of sedgelike Co3O4 nanoarrays allow unimpeded OH– ion diffusion, and the bundled structure provides flake-off resistance/mechanical stability during harmonious redox reactions with 2D Bi2O3 during high rate operation of the ASC device. It is proposed that the all-new Co3O4 || Bi2O3 asymmetric assimilation will open new avenues in the designing of high rate ASCs for power grid applications.

High-Performance All-Solid-State Flexible Asymmetric Supercapacitor Device Based on a Ag–Ni Nanoparticle-Decorated Reduced Graphene Oxide Nanocomposite as an Advanced Cathode Material

“…A remarkable high energy density of 49 W h kg –1 was attained at a power density of 1700 W kg –1 with an aqueous electrolyte system. These results are analogous and surpassing the substantive findings in the literature − along with the existing commercialized supercapacitors (Table S1).…”

Co3O4/NiCo2O4 Perforated Nanosheets for High-Energy-Density All-Solid-State Asymmetric Supercapacitors with Extended Cyclic Stability

“…The peaks (cathodic and anodic) in the CV profiles are attributed to the following faradic reactions In the CV profiles, the characteristics peaks due to oxidation (anodic) and reduction (cathodic) reactions are almost identical, which implies kinetic reversibility during the faradic reactions . The kinetic reversibility can also be manifested from the significant linearity ( R 2 = 0.98) in the ( E O – E R ) vs (ν) 1/2 plot, which is shown as inset I in Figure A.…”

Facile Synthesis of Manganese‐Cobalt‐Sulfur/Reduced Rraphene Oxide Composite as High Performing Faradaic Electrode

“…Figure 5a shows the CV curve of MCS/rGO composite electrode at various scan rates. Based on the CV profile, the characteristic peaks induced by the oxidation (anode) and reduction (cathode) reactions are almost similar, which implies its good kinetic reversibility during the faradaic reaction [28] . As shown in Figure 5a, as the scan rate increases from 1 mV s −1 to 10 mV s −1 , there is a gradual increase in the enclosed area of the CV curve.…”

“…Based on the CV profile, the characteristic peaks induced by the oxidation (anode) and reduction (cathode) reactions are almost similar, which implies its good kinetic reversibility during the faradaic reaction. [28] As shown in Figure 5a, as the scan rate increases from 1 mV s À 1 to 10 mV s À 1 , there is a gradual increase in the enclosed area of the CV curve. However, it is noted that even though the shape of the redox peak for all CV curves remain relatively unchanged, the positions of the reduction peak and the oxidation peak have shifted to the low and high potentials, respectively.…”