Ultrasound assisted synthesis of Mn3O4 nanoparticles anchored graphene nanosheets for supercapacitor applications

Mn3O4 nano-octahedrons embedded in nitrogen-doped graphene oxide as potent anode material for lithium-ion batteries

Mn3O4 nano-octahedrons embedded in N-doped graphene oxide (MNGO) nanosheets were synthesized using a simple, energy-efficient, and rapid microwave-digested hydrothermal route in a single step. The structural and morphological aspects of synthesized materials were evaluated by XRD, IR, Raman, FE-SEM, and HR-TEM techniques. Then, the composite MNGO was tested for its Li-ion storage properties and compared with reduced graphene oxide (rGO) and Mn3O4 materials. The MNGO composite exhibited superior reversible specific capacity, excellent cyclic stability, and outstanding structural integrity throughout the electrochemical studies. The MNGO composite showed a reversible capacity of 898 mA h g-1 after 100 cycles at 100 mA g-1 and Coulombic efficiency of 97.8%. Even at a higher current density of 500 mA g-1, it exhibits a higher specific capacity of 532 mA h g-1 (~1.5 times higher than commercial graphite anode). These results demonstrate that Mn3O4 nano-octahedrons embedded on N-doped GO are a highly durable and potent anode material for LIBs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11581-023-05035-6.

Augmenting the electrochemical performance of NiMn2O4 by doping of transition metal ions and compositing with rGO

The transition metal ions (TMIs) such as Co²⁺ and Zn²⁺ doped NiMn₂O₄ (NMO)/rGO nanocomposite synthesized by facile sol-gel method was used for the fabrication of supercapacitor. The presence of metal ions in the nanocomposite was confirmed by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscope (HR-TEM) mapping techniques. The fabricated electrode showed high specific capacitance of 710 F/g which was 3-fold higher than NMO (254 F/g). The addition of RGO in the nanocomposite increased the cycle stability of TMIs doped NMO significantly from 51 to 91%. In addition, the symmetric supercapacitor (SSC) fabricated using TMIs doped NMO/rGO nanocomposite with 3.5 M KOH as an electrolyte delivered a maximum energy density of 43 Wh/kg and power density of 10 kW/kg. Furthermore, the SSC device retained 90% of capacitance retention over 10,000 cycles with coulombic efficiency of 99% at 5 A/g. These result suggested that the TMIs doped NMO/rGO nanocomposite electrode is a promising material for high-energy supercapacitors.

Synthesis of Cu-Doped Mn3O4@Mn-Doped CuO Nanostructured Electrode Materials by a Solution Process for High-Performance Electrochemical Pseudocapacitors

Cu-doped Mn3O4 and Mn-doped CuO (CMO@MCO) mixed oxides with isolated phases together with pristine Mn3O4 (MO) and CuO (CO) have been synthesized by a simple solution process for applications in electrochemical supercapacitors. The crystallographic, spectroscopic, and morphological analyses revealed the formation of all of the materials with good crystallinity and purity with the creation of rhombohedral-shaped MO and CMO and a mixture of spherical and rod-shaped CO and MCO nanostructures. The ratio of CMO and MCO in the optimized CMO@MCO was 2:1 with the Cu and Mn dopants percentages of 12 and 15%, respectively. The MO-, CO-, and CMO@MCO-modified carbon cloth (CC) electrodes delivered the specific capacitance (C s) values of 541.1, 706.7, and 997.2 F/g at 5 mV/s and 413.4, 480.5, and 561.1 F/g at 1.3 A/g, respectively. This enhanced C s value of CMO@MCO with an energy density and a power density of 78.0 Wh/kg and 650.0 W/kg, respectively, could be attributed to the improvement of electrical conductivity induced by the dopants and the high percentage of oxygen vacancies. This corroborated to a decrease in the optical band gap and charge-transfer resistance (R ct) of CMO@MCO at the electrode/electrolyte interface compared to those of MO and CO. The net enhancement of the Faradaic contribution induced by the redox reaction of the dopant and improved surface area was also responsible for the better electrochemical performance of CMO@MCO. The CMO@MCO/CC electrode showed high electrochemical stability with a C s loss of only ca. 4.7%. This research could open up new possibilities for the development of doped mixed oxides for high-performance supercapacitors.

Ultrasound-assisted synthesis of unzipped multiwalled carbon nanotubes/titanium dioxide nanocomposite as a promising next-generation energy storage material

Carbon-based systems have been discussed as prospective alternatives for conventional metal-based catalysts over the past decade. These studies were motivated by the abundance, low cost, lightweight and diversity of structural allotropes of carbon. We reported here the synthesis of a new type of unzipped multiwalled carbon nanotubes/titanium dioxide (UzMWCNT/TiO₂) nanocomposite by the two-stage procedure. By the modified Hummers method, multiwalled carbon nanotubes (MWCNTs) were converted to oxidized multi-walled carbon nanotubes (O-MWCNT). Then, through a facile ultrasound-assisted route prepared UzMWCNT/TiO₂ nanocomposite. For this, the oxidized multiwalled carbon nanotubes are treated with TiCl₄ under an ultrasonic probe for 3 h to generate UzMWCNT/TiO₂ and then explored its environmental friendliness and energy applications as a supercapacitor. This novel UzMWCNT/TiO₂ nanocomposite was characterized using XRD, TGA, FT-IR, Raman, TEM and EDX analysis. The electrochemical performance can be evaluated by using cyclic voltammetry (CV) and galvanostatic charging-discharging (GCD) study. Finally, the electrodes prepared using UzMWCNT/TiO₂ nanocomposite have been analyzed through electrochemical impedance spectroscopy (EIS) to probe the charge transfer characteristics and the results are consistent with other electrochemical measurements.

Producing "Symbiotic" Reduced Graphene Oxide/Mn3O4 Nanocomposites Directly from Converting Graphite for High-Performance Supercapacitor Electrodes

Almost all existing methods for preparing reduced graphene oxide/Mn₃O₄ (RGO/Mn₃O₄) composites are based on the synthetized graphene or graphene oxides (GO), which make them complicated and high-cost processes. Here, we reported a new method, which is able to convert graphite directly to RGO/Mn₃O₄ composites. Thus, it is simpler, more economical, and productive. The structure of RGO/Mn₃O₄ inheriting intermediate product GO/MnO₂ composites that are formed by the present method is a novel three-dimensional "multilayer steamed bread" nanostructure, which constitutes mutually beneficial "symbiosis". The nano-Mn₃O₄ supports the space between RGO layers and further to the combination of RGO to self-assemble into large-sized (>40 μm) nanocomposites. Meanwhile, the formed Mn₃O₄ particles were small (60 × 10 nm²) in diameter and distributed homogeneously without the use of any template and surfactant. Because the structure and nanosize of composite cause the excellent electrochemical properties, RGO/Mn₃O₄ electrodes deliver an enhanced specific capacitance of 438.7 F/g at 0.3 A/g and outstanding cyclic stability (77.5% of its initial capacitance is retained after 1000 cycles).

Greatly Enhanced Faradic Capacities of 3D Porous Mn3O4/G Composites as Lithium-Ion Anodes and Supercapacitors by C-O-Mn Bonding

Through C-O-Mn bonding, graphene nanosheets are homogeneously dispersed in porous Mn₃O₄ to take full advantages of porous Mn₃O₄ and graphene nanosheets, making the as-formed three-dimensional porous Mn₃O₄/reduced graphene oxide (rGO) composite exhibit good electrochemical performance. Besides, C-O-Mn bonding is demonstrated to greatly promote the Faradic reactions of the composite, resulting in the enhancement of its real capacity in supercapacitor (SC) electrodes as well as lithium-ion battery (LIB) anodes. By simply fine-tuning the content of graphene (<7 wt %), the composite with 2.8 wt % of rGO delivers a high capacitance of 315 F g^-1 at 0.5 A g^-1 with a high rate capability of 64.7% at 30 A g^-1 and an excellent cycling stability of 105% (5 A g^-1, 5000 cycles) as an SC electrode. Also, the one with 6.9 wt % rGO can present a reversible capacity of more than 1500 mAh g^-1 at 0.05 A g^-1 as the LIB anode, the highest value reported to date, which remains 561 mAh g^-1 at 1 A g^-1.

In situ mass change and gas analysis of 3D manganese oxide/graphene aerogel for supercapacitors

Manganese oxide nanoparticles decorated on 3D reduced graphene oxide aerogels (3D MnO_x/rGO_ae) for neutral electrochemical capacitors were successfully produced by a rapid microwave reduction process within 20 s.

Sonochemical synthesis of Co2SnO4 nanocubes for supercapacitor applications

In this work, a simple sonochemical route was followed to synthesize cobalt stannate (Co₂SnO₄) nanocubes using stannous and cobalt chlorides as the precursors in alkaline medium at room temperature. The structure, composition and surface morphology of synthesized Co₂SnO₄ nanocubes have been characterized by using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) indicates that the Co₂SnO₄ nanocubes are crystalline, single-phase without any impurity phase; the sizes of nanocubes are ∼100 nm. The cyclic voltammetry, galvanostatic charge-discharge cycling test, and electrochemical impedance spectroscopy (EIS) measurements are carried out for the Co₂SnO₄ nanocubes shows a specific capacitance 237 F g^-1 at 0.5 mA cm^-2 current density and in 1 M Na₂SO₄ electrolyte. Co₂SnO₄ nanocubes exhibit long cycling life with 80% retention of initial capacitance after 2000 cycles and the excellent rate capability at 15 mA cm^-2 as much as 70% of that at 0.5 mA cm^-2 suggest its potential use for supercapacitor applications.

Performance enhancement of asymmetric supercapacitors with bud-like Cu-doped Mn3O4 hollow and porous structures on nickel foam as positive electrodes

Cu-doped Mn₃O₄ hollow nanostructures supported on Ni foams as high-performance electrode materials for supercapacitors were successfully synthesized through a facile hydrothermal method and subsequent calcination. The morphology, structure, and electrochemical performance of the as-prepared Mn₃O₄ nanostructures can be tuned just by varying the Cu doping content. Benefiting from the unique bud-like hollow structure, the 1.5 at% Cu-doped Mn₃O₄ sample has a high specific capacitance of 257.6 F g⁻¹ at 1 A g⁻¹ and remarkable stability (about 90.6% retention of its initial capacitance after 6000 electrochemical cycles). Besides, an asymmetric supercapacitor (ASC) cell based on the 1.5 at% Cu-doped Mn₃O₄ exhibits a high specific capacitance of 305.6 F g⁻¹ at 1 A g⁻¹ and an energy density of 108.6 W h kg⁻¹ at a power density of 799.9 W kg⁻¹. More importantly, the ASC shows good long-term stability with 86.9% capacity retention after charging/discharging for 6000 cycles at a high current density of 5 A g⁻¹.

The effect of Cu doping on the electrochemical performance of bud-like Mn₃O₄ nanostructures for supercapacitor application was comparatively investigated.

Synthesis of coaxial carbon@NiMoO4 composite nanofibers for supercapacitor electrodes

This work reports the synthesis of coaxial carbon@NiMoO₄ nanofibers for supercapacitor electrode applications. Thin NiMoO₄ nanosheets are uniformly coated on the conductive electrospun carbon nanofibers by a microwave assisted hydrothermal method to form a hierarchical structure, which increases the porosity as well as the conductivity of the electrode. The thickness of the NiMoO₄ can be easily adjusted by varying the precursor concentrations. The high specific surface area (over 280 m² g⁻¹) and conductive carbon nanofiber backbone increase the utilization of the active pseudocapacitive NiMoO₄ phase, resulting a high specific capacitance of 1840 F g⁻¹.

This work reports the synthesis of coaxial carbon@NiMoO₄ nanofibers for supercapacitor electrode applications.

Self-assembled Mn3O4 nano-clusters over carbon nanotube threads with enhanced supercapacitor performance

Self-assembled Mn₃O₄@CNT nano-clusters with improved capacitance and cyclic stability designed for supercapacitor application.

Reduced graphene oxide-mediated synthesis of Mn3O4 nanomaterials for an asymmetric supercapacitor cell

Herein, Mn₃O₄/reduced graphene oxide composites are prepared via a facile solution-phase method for supercapacitor application. Transmission electron microscopy results reveal the uniform distribution of Mn₃O₄ nanoparticles on graphene layers. The morphology of the Mn₃O₄ nanomaterial is changed by introducing the reduced graphene oxide during the preparation process. An asymmetric supercapacitor cell based on the Mn₃O₄/reduced graphene oxide composite with the weight ratio of 1 : 1 exhibits relatively superior charge storage properties with higher specific capacitance and larger energy density compared with those of pure reduced graphene oxide or Mn₃O₄. More importantly, the long-term stability of the composite with more than 90.3% capacitance retention after 10 000 cycles can ensure that the product is widely applied in energy storage devices.

The existence presence of rGO can affect the morphology of an Mn₃O₄/rGO composite, and the asymmetric supercapacitor cell created with this composite exhibits good capacitive performance.

Charge storage mechanisms of electrospun Mn3O4 nanofibres for high-performance supercapacitors

Mixed oxidation states of manganese oxides are widely used as the electrodes in supercapacitors due to their high theoretical pseudocapacitances.

Nitrogen doping in the carbon matrix for Li-ion hybrid supercapacitors: state of the art, challenges and future prospective

Li ion hybrid supercapacitors are summarized with an emphasis on the use of nitrogen doped graphene and activated carbons.

Boron–manganese–carbon nanocomposites synthesized from CO2 for electrode applications in both supercapacitors and fuel cells

Boron–manganese–carbon nanocomposites were synthesized from CO₂ for electrode materials in supercapacitor and fuel cell.

Hybrid SnO2–Co3O4 nanocubes prepared via a CoSn(OH)6 intermediate through a sonochemical route for energy storage applications

A cubic-like nanostructured SnO₂–Co₃O₄ hybrid was sonochemically synthesized via CoSn(OH)₆ nanocubes as an intermediate for supercapacitor application.

Synthesis of morphology-controlled bismutite for selective applications

Bismutite (Bi₂O₂CO₃) possessing diverse morphologies, namely, nanosheets, nanodiscs and nanoplatelets, was synthesized by a simple controllable method shows excellent materials as adsorbents and photocatalysts for wastewater treatment with supercapacitor activities for energy applications.

Microwave-assisted in situ synthesis of reduced graphene oxide/Mn3O4 composites for supercapacitor applications

Rationally designed reduced graphene oxide/Mn₃O₄ (GM) was achieved and GM showed long-stability capacitance after 5000 cycles at 1 A g⁻¹.

One step hydrothermal synthesis of Mn3O4/graphene composites with great electrochemical properties for lithium-ion batteries

Mn₃O₄/graphene electrodes exhibit a high capacity of ca. 500 mA h g⁻¹ at 60 mA g⁻¹ even after 100 cycles.

Low temperature self-assembled synthesis of hexagonal plate-shape Mn3O4 3D hierarchical architectures and their application in electrochemical capacitors

Low temperature self-assembled synthesis of hexagonal plate-shape Mn₃O₄ 3D hierarchical architectures and their application in electrochemical capacitors.