One-Step Controllable Synthesis of Mesoporous MgCo2 O4 Nanosheet Arrays with Ethanol on Nickel Foam as an Advanced Electrode Material for High-Performance Supercapacitors

Synergistic Charge Storage Enhancement in Supercapacitors via Ti3C2Tx MXene and CoMoO4 Nanoparticles

MXene has emerged as a highly promising two-dimensional (2D) layered material with inherent advantages as an electrode material, such as a high electrical conductivity and spacious layer distances conducive to efficient ion transport. Despite these merits, the practical implementation faces challenges due to MXene's low theoretical capacitance and issues related to restacking. In order to overcome these limitations, we undertook a strategic approach by integrating Ti3C2Tx MXene with cobalt molybdate (CoMoO4) nanoparticles. The CoMoO4 nanoparticles bring to the table rich redox activity, high theoretical capacitance, and exceptional catalytic properties. Employing a facile hydrothermal method, we synthesized CoMoO4/Ti3C2Tx heterostructures, leveraging urea as a size-controlling agent for the CoMoO4 precursors. This innovative heterostructure design utilizes Ti3C2Tx MXene as a spacer, effectively mitigating excessive agglomeration, while CoMoO4 contributes its enhanced redox reaction capabilities. The resulting CoMoO4/Ti3C2Tx MXene hybrid material exhibited 698 F g-1 at a scan rate of 5 mV s-1, surpassing that of the individual pristine Ti3C2Tx MXene (1.7 F g-1) and CoMoO4 materials (501 F g-1). This integration presents a promising avenue for optimizing MXene-based electrode materials, addressing challenges and unlocking their full potential in various applications.

Facile hydrothermal synthesis of porous MgCo2O4 nanoflakes as an electrode material for high-performance asymmetric supercapacitors

In this work, porous MgCo₂O₄ nanoflakes (MgCo₂O₄ NFs) and MgCo₂O₄ nanocubes (MgCo₂O₄ NCs) have been successfully synthesized through a simple hydrothermal method combined with a post calcination process of the precursor in air. The morphology of the MgCo₂O₄ samples can be easily tuned by changing the hydrothermal temperature and reaction time, respectively. The porous MgCo₂O₄ NFs with an average pore size of 12.5 nm had a BET specific surface area up to 64.9 m² g^-1, which was larger than that of MgCo₂O₄ NCs (19.8 m² g^-1). The MgCo₂O₄ NFs delivered a specific capacitance of 734.1 F g^-1 at 1 A g^-1 and exhibited a considerable rate performance with 74.0% capacitance retention at 12 A g^-1. About 94.2% of its original capacitance could be retained after 5000 charge-discharge cycles at a constant current density of 5 A g^-1. An asymmetric supercapacitor (ASC) was assembled by using MgCo₂O₄ NFs as the positive electrode and AC as the negative electrode, and the ASC had a wide operation voltage of 1.7 V and a high energy density of 33.0 W h kg^-1 at a power density of 859.6 W kg^-1. Such outstanding electrochemical performances make the MgCo₂O₄ NFs a promising candidate for supercapacitor applications. In addition, the simple and scalable synthesis method can be extended to the preparation of other metal oxide-based electrode materials.

Facile preparation of hierarchical MgCo2O4/MgCo2O4 nanochain array composites on Ni foam as advanced electrode materials for supercapacitors

Schematic illustration of the two-step synthesis of MgCo₂O₄/MgCo₂O₄ directly grown on Ni foam.

Fluoride ion assisted growth of hierarchical flowerlike nanostructures of Co/Ni ferrites and their magnetoresistive response

One-dimensional nanorod arrays exhibiting hierarchical flowerlike morphologies, of Co and Ni based ferrites were synthesized by hydrothermal treatment and using ammonium fluoride (NH₄F) as a mineralizing agent. The effects of NH₄F concentration and synthesis temperature were probed to control the morphology of these nanorods that were formed as a result of crystal nucleation. It was observed that a higher concentration of NH₄F leads to several other nucleation sites above these nanorods while controlled concentration of precursors and NH₄F results in the synthesis of floral patterns. The specific geometries of these nanorods leads to a shape anisotropy effect resulting in increased magnetic coercive fields. To study the effect of magnetic field on the resistance and current density, impedance spectroscopy and I–V–R characteristics, respectively, were performed. Nanorods show enhanced values for resistance with the increase in magnetic field confirming the effect of magnetoresistive coupling while a decrease in current densities with increasing magnetic field highlights the potential of these structures for magnetoresistive applications.

One-dimensional nanorod arrays of Co/Ni ferrites emerging into hierarchical flowerlike morphologies, prepared by hydrothermal treatment, using ammonium fluoride (NH₄F) as a mineralizing agent.

Construction of NiCo2O4 nanosheet-decorated leaf-like Co3O4 nanoarrays from metal–organic framework for high-performance hybrid supercapacitors

Leaf-like Co₃O₄@NiCo₂O₄ nanoarrays with an excellent energy storage performance was designed by a MOF-guided strategy.