Synthesis of novel Co3O4 nanocubes-NiO octahedral hybrids for electrochemical energy storage supercapacitors

Ternary g-C3N4/Co3O4/CeO2 nanostructured composites for electrochemical energy storage supercapacitors

Extensive use of fossil fuels causes heavy discharge of carbon dioxide, depleting energy resources and this requires environmentally friendly and effective energy storage materials. Hybrid supercapacitors (HSCs) are recently developed as effective energy storage materials enabling high capacitance retention rate and quick charging. Herein, synthesis of two-dimensional g-C3N4 nanosheets supported onto three-dimensional flower-like Co3O4/CeO2 (CoCe) ternary synergistic heterostructures are developed as effective electrodes for hybrid supercapacitor applications. Addition of g-C3N4 produces substantial surface active sites, enabling its synergistic effect with CoCe to enhance electrochemical performance having exceptional conductivity. The CoCe/g-C3N4 ternary composite electrode exhibits a higher specific capacitance of 1088.3 F g-1 at 1 A g-1 with 96 % of recycling stability over 5000 cycles, which is ∼5.5 and ∼5 folds higher specific capacitance than the pristine g-C3N4 and CoCe electrodes. EIS analysis revealed that CoCe/g-C3N4 electrode offered reduced charge transfer resistance compared to pristine electrodes. The fabricated two-electrode HSC device displays outstanding retention after 10,000 cycles with an ultra-high specific capacitance of 119.8 F g-1, excellent energy density 37.4 Wh kg-1 and power density of 749.9 W kg-1. This research showcases the perspectives of CoCe/g-C3N4 ternary electrodes in hybrid supercapacitors and other renewable energy storage devices.

Multifunctional hybrid films made from CoT3OTx4 and CoFeT2OT4 nanoparticles inside a poly 3-hydroxybutyrate matrix and study of their impact in methyl orange photodegradation

This work aims to produce hybrid materials with potential applications in dye photodegradation. Therefore, hybrid films were obtained by incorporating cobalt (II, III) oxide (Co3O4) or cobalt ferrite (CoFe2O4) nanoparticles (NPs) with 18 ± 1.6 nm and 26 ± 1.3 nm, respectively, into a poly 3-hydroxybutyrate (P3HB) polymeric matrix. The Co3O4@P3HB and CoFe2O4@P3HB hybrid films were fabricated by solvent casting in a ratio of 85 mg to 15 mg (P3HB-NPs). Different spectroscopic and microscopy techniques characterized the Co3O4 and CoFe2O4 NPs and the P3HB, Co3O4@P3HB and CoFe2O4@P3HB films. The optical band gap for Co3O4 and CoFe2O4 NPs was estimated from their diffuse reflectance spectra (DRS) around 2.5 eV. X-ray diffraction (XRD) of the hybrid films revealed that the nanometric sizes of the Co3O4 and CoFe2O4 nanoparticles incorporated into the P3HB are preserved. The magnetic hysteresis curve of CoFe2O4 nanoparticles and CoFe2O4@P3HB film showed a ferromagnetic behaviour at 300 K. Transmission electron microscopy (TEM) confirmed the formation of nanocrystals, and scanning electron microscopy (SEM) provided evidence for the successful incorporation of the NPs into the P3HB matrix. The surface roughness and hydrophilicity of the hybrid films are increased compared to the P3HB film. The impact of the nanoparticles and the hybrid films on the photodegradation of methyl orange (MO) in its acidic form was studied. The photodegradation tests were carried out by direct sunlight exposure. The CoFe2O4@P3HB hybrid film achieved 85% photodegradation efficiency of a methyl orange solution of 20 ppm after 15 minutes of exposure to sunlight. After 30 minutes of exposure to sunlight, the nanoparticles and the hybrid films reached about 90% of the MO degradation. The results suggest that combining nanoparticles with the polymer significantly enhances photodegradation compared to isolated nanoparticles.

Biogenic synthesis of nickel cobaltite nanoparticles via a green route for enhancing the photocatalytic and electrochemical performances

Green synthesis aligns with the global demand for eco-friendly and sustainable technologies, reducing the dependency on harmful chemicals and high-energy processes typically used in conventional synthesis techniques. This study highlights a novel green synthesis route for nickel cobaltite nanoparticles (NiCO2O4 NPs) utilizing Hyphaene thebaica extract as a natural reducing and stabilizing agent. The synthesized NiCO2O4 NPs, with sizes ranging from 20 to 30 nm, exhibited uniform diamond-like structures as confirmed by SEM and TEM imaging. XRD analysis verified the polycrystalline nature of these nanoparticles, while EDS measurements confirmed the elemental composition of Ni and Co. The presence of functional groups was subsequently verified through FT-IR analysis, and Raman spectroscopy further confirmed phase formation. Electrochemical evaluations revealed significant pseudocapacitive behavior, showing a specific capacitance of 519 F/g, demonstrating their potential for high-performance supercapacitors. To further assess the applicability of the synthesized NiCO2O4 NPs, their photocatalytic activity against methylene blue (MB) dye was investigated, resulting in a 99% degradation rate. This impressive photocatalytic efficiency highlights their potential application in environmental remediation. Overall, this work underscores the significant potential of green synthesis methods in producing high-performance nanomaterials while simultaneously reducing environmental impact and promoting sustainable development.

Novel rhombus Co3O4-nanocapsule CuO heterohybrids for efficient photocatalytic water splitting and electrochemical energy storage applications

The most appealing and prominent approach for improving energy storage and conversion performance is the development of heterojunction interfaces with efficient and unique metal oxide nanostructures. Rhombus Co₃O₄, nanocapsule CuO, and their heterojunction composites were synthesized using a single-step hydrothermal process. The resulting heterojunction Co₃O₄-CuO nanocomposite outperformed the pristine Co₃O₄ and CuO nanostructures for the electrochemical supercapacitor and water splitting performances. The composite showed 2.4 and 1.3 times higher specific capacitance than the associated pristine CuO and Co₃O₄ nanostructures, while its capacitance was 395 F g^-1 at a current density of 0.5 A g^-1. In addition, long-term GCD results with more than 90% stability and significant capacity retention at higher scan rates revealed the unaffected structures interfaced during the electrochemical reactions. The composite photoelectrode demonstrated more than 20% of photocurrent response with light illumination than the dark condition in water splitting. Co₃O₄-CuO heterostructured composite electrode showed a 0.16 mA/cm² photocurrent density, which is 3.2 and 1.7 times higher than the pristine CuO and Co₃O₄ electrodes, respectively. This performance was attributed to its unique structural composition, high reactive sites, strong ion diffusion, and fast electron accessibility. Electron microscopic and spectroscopic techniques confirmed the properties of the electrodes as well as their morphological properties. Overall, the heterojunction interface with novel rhombus and capsule structured architectures showed good electrochemical performance, suggesting their energy storage and conversion applications.

g-C3N4 nanosheets functionalized yttrium-doped ZrO2 nanoparticles for efficient photocatalytic Cr(VI) reduction and energy storage applications

Novel g-C₃N₄ functionalized yttrium-doped ZrO₂ hybrid heterostructured (g-YZr) nanoparticles have been synthesized to investigate photocatalytic Cr(VI) reduction as well as electrochemical energy storage applications. The nanoparticles have been characterized to examine their structural, optical, and photocatalytic properties. XRD confirmed the incorporation of dopant ions and heterostructure development between g-C₃N₄ and doped ZrO₂. When g-C₃N₄ was doped with ZrO_2, the ability of light adsorption was greatly enhanced due to the narrow band gap. The distinctive structure of g-YZr exhibited outstanding photocatalytic Cr(VI) reduction owing to its superior surface area, which greatly prevented the charge carriers' recombination rate and exhibited superior photocatalytic performance within 90 min of solar light irradiation. Furthermore, these catalysts demonstrated similar catalytic Cr(VI) reduction activity following four repeatability tests, indicating the exceptional structural stability of g-YZr catalysts. The electrochemical performance of the electrodes revealed that g-YZr exhibited superior specific capacitance over the other electrodes owing to extra energetic sites and robust synergic effect. Enhanced specific capacitance and long cyclic stability of the hybrid heterostructures displayed their usefulness for energy storage applications.