High electrochemical performance asymmetric supercapacitor based on La 2 O 3 //Co 3 O 4 electrodes

Engineering of Co3O4 electrode via Ni and Cu-doping for supercapacitor application

Although cobalt oxides show great promise as supercapacitor electrode materials, their slow kinetics and low conductivity make them unsuitable for widespread application. We developed Ni and Cu-doped Co3O4 nanoparticles (NPs) via a simple chemical co-precipitation method without the aid of a surfactant. The samples were analyzed for their composition, function group, band gap, structure/morphology, thermal property, surface area and electrochemical property using X-ray diffraction (XRD), ICP-OES, Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV-Vis), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and/or Differential thermal analysis (DTA), Brunauer-Emmett-Teller (BET), and Impedance Spectroscopy (EIS), Cyclic voltammetry (CV), respectively. Notably, for the prepared sample, the addition of Cu to Co3O4 NPs results in a 11.5-fold increase in specific surface area (573.78 m2 g-1) and a decrease in charge transfer resistance. As a result, the Ni doped Co3O4 electrode exhibits a high specific capacitance of 749 F g-1, 1.75 times greater than the pristine Co3O4 electrode's 426 F g-1. The electrode's enhanced surface area and electronic conductivity are credited with the significant improvement in electrochemical performance. The produced Ni doped Co3O4 electrode has the potential to be employed in supercapacitor systems, as the obtained findings amply demonstrated.

Fabrication of fullerene-supported La2O3-C60 nanocomposites: dual-functional materials for photocatalysis and supercapacitor electrodes

Nowadays, water pollution and energy crises worldwide force researchers to develop multi-functional and highly efficient nanomaterials. In this scenario, the present work reports a dual-functional La₂O₃-C₆₀ nanocomposite fabricated by a simple solution method. The grown nanomaterial worked as an efficient photocatalyst and proficient electrode material for supercapacitors. The physical and electrochemical properties were studied by state-of-the-art techniques. XRD, Raman spectroscopy, and FTIR spectroscopy confirmed the formation of the La₂O₃-C₆₀ nanocomposite with TEM nano-graphs, and EDX mapping exhibits the loading of C₆₀ on La₂O₃ particles. XPS confirmed the presence of varying oxidation states of La³⁺/La²⁺. The electrochemical capacitive properties were tested by CV, EIS, GCD, ECSA, and LSV, which indicated that the La₂O₃-C₆₀ nanocomposite can be effectively used as an electrode material for durable and efficient supercapacitors. The photocatalytic test using methylene blue (MB) dye revealed the complete photodegradation of the MB dye under UV light irradiation after 30 min by a La₂O₃-C₆₀ catalyst with a reusability up to 7 cycles. The lower energy bandgap, presence of deep-level emissions, and lower recombination rate of photoinduced charge carriers in the La₂O₃-C₆₀ nanocomposite than those of bare La₂O₃ are responsible for enhanced photocatalytic activity with low-power UV irradiation. The fabrication of multi-functional and highly efficient electrode materials and photocatalysts such as La₂O₃-C₆₀ nanocomposites is beneficial for the energy industry and environmental remediation applications.

Ag doped Co3O4 nanoparticles for high-performance supercapacitor application

Ag doped Co₃O₄ nanoparticles (NPs) were synthesized via a co-precipitation method changing the concentration of Ag. The crystal structure, morphology, surface area, functional group, optical band gap, and thermal property were investigated by XRD, SEM, BET, FTIR, UV-Vis, and TGA/DTA techniques. The XRD results showed the formation of single-cubic Co₃O₄ nanostructured materials with an average crystal size of 19.37 nm and 12.98 nm for pristine Co₃O₄ and 0.25 M Ag-doped Co₃O₄ NPs. Morphological studies showed that pristine Co₃O₄ and 0.25 M Ag-doped Co₃O₄ NPs having a porous structure with small spherical grains, porous structures with sponge-like structures, and loosely packed porous structures, respectively. The pristine and 0.25 M Ag-doped Co₃O₄ NPs showed BET surface areas of 53.06 m²/g, and 407.33 m²/g, respectively. The band gap energy of Co₃O₄ NPs were 2.96 eV, with additional sub-bandgap energy of 1.95 eV. Additionally, it was discovered that the band gap energies of 0.25 M Ag-doped Co₃O₄ NPs ranged from 2.2 to 2.75 eV, with an extra sub-band with energies ranging from 1.43 to 1.94 eV for all as-prepared samples. The Ag-doped Co₃O₄ as prepared samples show improved thermal properties due to the doping effect of silver. The CV test confirmed that the 0.25 M Ag-doped Co₃O₄ NPs exhibited the highest specific capacitance value of 992.7 F/g at 5 mV/s in a 0.1 M KOH electrolyte solution. The energy density and power density of 0.25 M Ag-doped Co₃O₄ NPs were 27.9 W h/kg and 3816.1 W/kg, respectively.

Enhanced Photocatalytic Degradation Activity Using the V2O5/RGO Composite

Semiconductor-based photocatalyst materials played an important role in the degradation of organic compounds in recent years. Photocatalysis is a simple, cost-effective, and environmentally friendly process for degrading organic compounds. In this work, vanadium pentoxide (V₂O₅) and V₂O₅/RGO (reduced graphene oxide) composite were synthesized by a hydrothermal method. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman spectroscopy, and UV-Vis spectroscopic analysis, etc. Raman analysis shows the occurrence of RGO characteristic peaks in the composite and different vibrational modes of V₂O₅. The band gap of flake-shaped V₂O₅ is reduced and its light absorption capacity is enhanced by making its composite with RGO. The photocatalytic degradation of methylene blue (MB) was studied using both V₂O₅ and V₂O₅/RGO composite photocatalyst materials. The V₂O₅/RGO composite exhibits a superior photocatalytic performance to V₂O₅. Both catalyst and light play an important role in the degradation process.

Rare Earth-Based Nanomaterials for Supercapacitors: Preparation, Structure Engineering and Application

Supercapacitors (SCs) can effectively alleviate problems such as energy shortage and serious greenhouse effect. The properties of electrode materials directly affect the performance of SCs. Rare earth (RE) is known as "modern industrial vitamins", and their functional materials have been listed as key strategic materials. In the past few years, the number of scientific reports on RE-based nanomaterials for SCs has increased rapidly, confirming that adding RE elements or compounds to the host electrode materials with various nanostructured morphologies can greatly enhance their electrochemical performance. Although RE-based nanomaterials have made rapid progress in SCs, there are very few works providing a comprehensive survey of this field. In view of this, a comprehensive overview of RE-based nanomaterials for SCs is provided here, including the preparation methods, nanostructure engineering, compounds, and composites, along with their capacitance performances. The structure-activity relationships are discussed and highlighted. Meanwhile, the future challenges and perspectives are also pointed out. This Review can not only provide guidance for the further development of SCs but also arouse great interest in RE-based nanomaterials in other research fields such as electrocatalysis, photovoltaic cells, and lithium batteries.

The electrochemical kinetics of cerium selenide nano-pebbles: the design of a device-grade symmetric configured wide-potential flexible solid-state supercapacitor

Next-generation portable flexible electronic appliances require liquid-free energy storage supercapacitor devices to eliminate leakage and to support mechanical bending that is compatible with roll-to-roll technologies. Hence, a state-of-the-art process is presented to design a solid-state, wide-potential and flexible supercapacitor through the use of nano-pebbles of cerium selenide via a simple successive ionic layer adsorption and reaction (SILAR) method that could allow an industry scalable route. We strongly believe that this is the first approach amongst physical and chemical routes not only for synthesizing cerium selenide in thin-film form but also using it for device-grade supercapacitor applications. The designed solid-state symmetric supercapacitor assembled from cerium selenide electrodes sandwiched by PVA-LiClO₄ gel electrolyte attains a wide potential window of 1.8 V with capacitance of 48.8 F g^-1 at 2 mV s^-1 and reveals excellent power density of 4.89 kW kg^-1 at an energy density of 11.63 W h kg^-1. The formed device is capable of 87% capacitive retention even at a mechanical bending angle of 175°. Lighting up a strip of 21 parallel connected red LEDs clearly demonstrates the practical use of the designed symmetric solid-state supercapacitor, aiming towards the commercialization of the product in the future.

Synthesis of multifunctional FeCo2O4 electrode using ultrasonic treatment for photocatalysis and energy storage applications

To overcome problem of energy crises, and water pollution, multifunctional nanoflower-like FeCo₂O₄ is synthesized for energy storage and photocatalysis applications. The nanoflower-like FeCo₂O₄ possesses charge transportation ability. The nanoflower-like morphology of FeCo₂O₄ is designed by simple hydrothermal synthesis with use of probe sonicator. The systematic analysis is performed for verify relevance of surface characteristics with electrochemical and photocatalytic properties of FeCo₂O₄ electrode. FeCo₂O₄ exhibits hierarchical flower-like nanostructure with high surface area and appropriate pore volume, which increases specific capacitance (Cs) up to 1230 F g^-1 with stability up to 5000 cycles. Degradation efficiency of crystal violet using FeCo₂O₄ photocatalyst is reached up to 94.19% under sunlight irradiation for 160 min.

Ultrasound assisted growth of NiCo2O4@carbon cloth for high energy storage device application

The nanostructure of metal oxides attracts great attention in the field of supercapacitors because of fast charge transport process. The hydrothermal method is used for development of NiCo₂O₄nanostructure on carbon cloth as current collector backbone. The stepwise study of various structural, morphological and electrochemical properties of NiCo₂O₄electrode is studied. The ultrasonic treatment is used to obtain nanowire-like morphology of NiCo₂O₄ which exhibits hierarchical nanostructure, which provides surface properties such as high surface area and appropriate pore capacity. NiCo₂O₄ nanostructure with specific capacitance of 1460 F g^-1 with high electrochemical stability of 84% after 3000 cycles in 3 M KOH aqueous electrolyte at 100 mV s^-1. The electrochemical property shows NiCo₂O₄is one of the potential candidates for energy storage application. The specific capacitance and energy density for NiCo₂O₄@CC//NiCo₂O₄@CC symmetric supercapacitor device is of 124 F g^-1 and 16.18 Wh.kg^-1, respectively at current density of 5 mA.