Enhanced supercapacitive performance of reduced graphene oxide by incorporating NiCo2O4 quantum dots using aqueous electrolyte

Facile Synthesis of 3D NC-rGO@Ni-Foam Nanonetwork as a Binder-Free Hybrid Electrode Material for Ultrahigh Capacitance Applications

In this study, a three-dimensional (3D) structured nanomaterial has been developed to enhance the electrochemical properties of supercapacitors. The nanomaterial's structure was engineered by incorporating divalent metal ions (M2+: Ni2+ and Co2+) into reduced graphene oxide (rGO) layers supported on nickel foam (3D NC-rGO@Ni-foam), forming a binder-free hybrid electrode. This was accomplished through a combination of in situ wet-chemistry and hydrothermal techniques. This binder-free electrode material has stacked layers of rGO, which improve conductivity, while the M2+ ions intercalated between these layers function as redox couples, thereby significantly improving the specific capacitance. Furthermore, the Ni-foam substrate offers a porous configuration and works as the current collector. In contrast to traditional slurry coating methods, the in situ growth of nanostructures on Ni-foam is expected to enhance strong adhesion, high conductivity, and effective ion transport. The structural morphology, chemical composition, and electrochemical behavior of the 3D NC-rGO@Ni-foam electrode were comprehensively investigated using techniques such as scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and other analytical methods. This binder-free 3D hybrid electrode material demonstrated a specific capacitance (C s) of 2612 F/g at 1 A/g. The symmetric device fabricated also demonstrated a substantial energy density (E) of 55 W·h/kg and a power density (P) of 155 W/kg across a wide potential window of 2.5 V. The electrochemical characteristics and mechanical stability of 3D NC-rGO@Ni-foam indicate its potential as a high-performance electrode material for scalable energy storage systems.

High electrochemical performance of nickel cobaltite@biomass carbon composite (NiCoO@BC) derived from the bark of Anacardium occidentale for supercapacitor application

Biomass carbon-based materials are highly promising for supercapacitor (SC) electrodes due to their availability, environment-friendliness, and low cost. Herein, an easy energy-saving hydrothermal process was used to produce NiCo2O4/NiOOH (NiCoO) composites with biomass carbon (BC) derived from the bark of Anacardium occidentale (AO) at different synthesis time durations (2 h, 4 h, 8 h, 16 h). The structural and morphological properties of the samples were analysed using XRD, Raman spectroscopy, XPS, SEM, TEM and BET, and the results exhibit the presence of carbon inserted into the nickel-cobalt hydroxide matrix. The NiCoO@BC composite synthesized in 4 h (NiCoO@BC(4 h)) displays a good specific capacitance of 475 F g-1 at 0.5 A g-1 and a low equivalent series resistance (ESR) value of 0.36 Ω. It shows a good coulombic efficiency of 98% and retains 86% of the capacitance after 4000 cycles. The asymmetric supercapacitor (ASC) device (NiCoO@BC(4 h)//AC) assembled using activated carbon (AC) as a negative electrode displays 20 W h kg-1 energy density and 900 W kg-1 power density at 1 A g-1. The stability test shows a good coulombic efficiency of 99% and 78% capacitance retention after 15 000 cycles. These findings imply that NiCoO@BC composites have outstanding electrochemical properties, making them suitable as SC electrode materials.

The first structural, morphological and magnetic property studies on spinel nickel cobaltite nanoparticles synthesized from non-standard reagents

In this paper, using a molten salt process, nickel cobaltite nanoparticles were successfully synthesized for the first time from non-standard reagents.

In-situ growth of cobalt manganate spinel nanodots on carbon black toward high-performance zinc-air battery: Dual functions of 3-aminopropyltriethoxysilane

Developing cost-effective and stable non-noble electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is now the critical issue for large-scale application of zinc-air batteries. Here, we presented a simple method to synthesize highly dispersed cobalt manganate spinel nanodots in-situ embedded in amine-functionalized carbon black. Silane coupling agent 3-aminopropyltriethoxysilane (APTES) played dual roles in the preparation: (1) to achieve amine-functionalization of carbon support; (2) as weak alkali to precipitate metal hydroxides which were then converted to spinel nanodots after mild calcination. The hydrophilicity of the carbon substrate was enhanced by amine modification from APTES to disperse metal oxide evenly, and the electrochemical activity was promoted through the strong interface interaction between embedded spinel nanodots and carbon substrate during the calcination process. As expected, the CoMn₂O₄/C-NH₂-300 catalyst exhibited satisfactory bifunctional catalytic performance for both ORR and OER with an ΔE (E_1/2-E_j10) = 0.75 V, which was lower than most state-of-the-art catalysts. In addition, CoMn₂O₄/C-NH₂-300 as a cathode also exhibited remarkable zinc-air battery performance in alkaline solution. This strategy of APTES as a bifunctional coupling agent provided a novel way to design and explore highly active, durable, and cost-effective catalysts for renewable energy conversion and storage.