Ag doped Co3O4 nanoparticles for high-performance supercapacitor application

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.

Dual Applications of Cobalt-Oxide-Grafted Carbon Quantum Dot Nanocomposite for Two Electrode Asymmetric Supercapacitors and Photocatalytic Behavior

Carbon materials, such as graphene, carbon nanotubes, and quantum-dot-doped metal oxides, are highly attractive for energy storage and environmental applications. This is due to their large surface area and efficient optical and electrochemical activity. In this particular study, a composite material of cobalt oxide and carbon quantum dots (Co3O4-CQD) was prepared using cobalt nitrate and ascorbic acid (carbon source) through a simple one-pot hydrothermal method. The properties of the composite material, including the functional groups, composition, surface area, and surface morphology, were evaluated by using various methods such as ultraviolet, Fourier transform infrared, X-ray diffraction, Raman, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller, scanning electron microscopy, and transmission electron microscopy analysis. The electrochemical performance of the Co3O4-CQD composite has been studied using a three-electrode system. The results show that at 1 A g-1, the composite delivers a higher capacitance of 1209 F g-1. The asymmetric supercapacitor (Co3O4-CQD//AC) provided 13.88 W h kg-1 energy and 684.65 W kg-1 power density with a 96% capacitance retention. The Co3O4-CQD composite also demonstrated excellent photocatalytic activity (90% in 60 min) for the degradation of methylene blue dye under UV irradiation, which is higher than that of pristine Co3O4 and CQD. This demonstrates that the Co3O4-CQD composite is a promising material for commercial energy storage and environmental applications.

Boosting the Electrochemical Storage Properties of Co3O4 Nanowires by the Mn Doping Strategy with Appropriate Mn Doping Concentrations

High specific capacitance, high energy density, and high power density have always been important directions for the improvement of electrode materials for supercapacitors. In this paper, Co3O4 nanowire arrays with various Mn doping concentrations (Mn:Co molar ratio = 1:11, 1:5, 1:2) directly grown on nickel foam (NF) were prepared by a simple hydrothermal method and annealing process. The influence of Mn doping on the morphology, structure, and electrochemical behaviors of Co3O4 was investigated. The results show that partial substitution of Co ions with Mn ions in the spinel structure does not change the nanowire morphology of pure Co3O4 but increases the lattice parameter and decreases the crystallinity of cobalt oxide. Electrochemical measurements showed that Mn doping in Co3O4 could effectively enhance the redox activity, especially Co3O4 with a Mn doping ratio of 1:5, which exhibits the most excellent electrochemical performance, with the maximum specific capacitance of 1210.8 F·g-1 at 1 A·g-1 and a rate capability of 33.0% at 30 A·g-1. The asymmetric supercapacitor (ASC) device assembled with the optimal Mn-Co3O4 (1:5) and activated carbon (AC) electrode performs a high specific capacitance of 105.8 F·g-1, a high energy density of 33 Wh·kg-1 at a power density of 748.1 W·kg-1, and a capacitance retention of 60.2% after 5000 cycles. This work indicates that an appropriate Mn doping concentration in the Co3O4 lattice structure will have great potential in rationalizing the design of spinel oxides for efficient electrochemical performance.

An experimental and computational study of graphene oxide functionalized with tris(hydroxymethyl)aminomethane as an electrode material for supercapacitors

In this research, graphene oxide (GO) functionalized with tris(hydroxymethyl)aminomethane (T) was synthesized with a simple one-pot method, and applied as an electrode material for supercapacitors. Electrochemical measurements on the synthesized tris(hydroxymethyl)aminomethane-functionalized graphene oxide (GO@T) indicated a specific capacitance of 549.8 F g- 1 at a specific current of 2.5 A g- 1 and a specific capacitance of 358 F g-1 at a specific current of 7 A g- 1 in the potential range of - 0.5-0.5 V versus Ag/AgCl. It also showed a high cyclic stability. According to the results, 80 and 68% of the initial capacitance was retained after 5500 and 9300 cycles, respectively. Density functional theory calculations were used to investigate the quantum capacitance, free energy change during functionalization reaction, and the layer distance of GO and GO@T.

Enhancing pseudocapacitive properties of cobalt oxide hierarchical nanostructures via iron doping

Through co-precipitation and post-heat processing, nanostructured Fe-doped Co₃O₄ nanoparticles (NPs) were developed. Using the SEM, XRD, BET, FTIR, TGA/DTA, UV-Vis, and techniques were examined. The XRD analysis presented that Co₃O₄ and Co₃O₄ nanoparticles that had been doped with 0.25 M Fe formed single cubic phase Co₃O₄ NPs with average crystallite sizes of 19.37 nm and 14.09 nm, respectively. The as prepared NPs have porous architectures via SEM analyses. The BET surface areas of Co₃O₄ and 0.25 M Fe-doped Co₃O₄ NPs were 53.06 m²/g and 351.56 m²/g, respectively. Co₃O₄ NPs have a band gap energy of 2.96 eV and an extra sub-band gap energy of 1.95 eV. Fe-doped Co₃O₄ NPs were also found to have band gap energies between 2.54 and 1.46 eV. FTIR spectroscopy was used to determine whether M-O bonds (M = Co, Fe) were present. The doping impact of iron results in the doped Co₃O₄ samples having better thermal characteristics. The highest specific capacitance was achieved using 0.25 M Fe-doped Co₃O₄ NPs at 5 mV/s, which corresponding to 588.5 F/g via CV analysis. Additionally, 0.25 M Fe-doped Co₃O₄ NPs had energy and power densities of 9.17 W h/kg and 472.1 W/kg, correspondingly.