In Situ Growth of Polypyrrole onto Three-Dimensional Tubular MoS2 as an Advanced Negative Electrode Material for Supercapacitor

One-Pot Effective Approach to 2,5-Diformylfuran From Carbohydrates Using MoS2-Decorated Carbonaceous Sugarcane Bagasse

Exploring the transformation of carbohydrates into valuable chemicals offers a promising and eco-friendly method for utilizing renewable biomass resources. Developing a bi-functional, sustainable heterogeneous catalyst is of utmost importance to attain a high level of selectivity for the desired product, 2,5-diformylfuran (DFF), in this direct conversion process. In this study, we developed a highly effective catalytic system to convert diverse carbohydrates into DFF. Our approach involved utilizing a MoS2 catalyst supported by amorphous carbon derived from sulfonated sugarcane biomass. The MoS2@SBG-SO3H composite was successfully synthesized using a facile and highly efficient method. The transformation of fructose into DFF achieved a significant yield of 70 % for 5 h at 160 °C using a one-step and one-pot reaction through dehydration and oxidation with oxygen. The oxidation of 5-hydroxymethylfurfural (HMF) into DFF using MoS2@SBG-SO3H was obtained at 94 % DFF within 5 h; the activation energy was 38.3 kJ . mol-1. The catalyst displayed convenient recovery and reusability. The direct synthesis of DFF from various carbohydrates, such as sucrose, glucose, maltose, and lactose, resulted in favorable yields. Our research provides a quick, green, and efficient process for preparing carbon-based solid acid catalysts and DFF.

Strategies for Advanced Supercapacitors Based on 2D Transition Metal Dichalcogenides: From Material Design to Device Setup

Recently, the development of new materials and devices has become the main research focus in the field of energy. Supercapacitors (SCs) have attracted significant attention due to their high power density, fast charge/discharge rate, and excellent cycling stability. With a lamellar structure, 2D transition metal dichalcogenides (2D TMDs) emerge as electrode materials for SCs. Although many 2D TMDs with excellent energy storage capability have been reported, further optimization of electrode materials and devices is still needed for competitive electrochemical performance. Previous reviews have focused on the performance of 2D TMDs as electrode materials in SCs, especially on their modification. Herein, the effects of element doping, morphology, structure and phase, composite, hybrid configuration, and electrolyte are emphatically discussed on the overall performance of 2D TMDs-based SCs from the perspective of device optimization. Finally, the opportunities and challenges of 2D TMDs-based SCs in the field are highlighted, and personal perspectives on methods and ideas for high-performance energy storage devices are provided.

High-Performance Flexible Energy Storage Devices Based on Graphene Decorated with Flower-Shaped MoS2 Heterostructures

MoS₂, owing to its advantages of having a sheet-like structure, high electrical conductivity, and benign environmental nature, has emerged as a candidate of choice for electrodes of next-generation supercapacitors. Its widespread use is offset, however, by its low energy density and poor durability. In this study, to overcome these limitations, flower-shaped MoS₂/graphene heterostructures have been deployed as electrode materials on flexible substrates. Three-electrode measurements yielded an exceptional capacitance of 853 F g^-1 at 1.0 A g^-1, while device measurements on an asymmetric supercapacitor yielded 208 F g^-1 at 0.5 A g^-1 and long-term cyclic durability. Nearly 86.5% of the electrochemical capacitance was retained after 10,000 cycles at 0.5 A g^-1. Moreover, a remarkable energy density of 65 Wh kg^-1 at a power density of 0.33 kW kg^-1 was obtained. Our MoS₂/Gr heterostructure composites have great potential for the development of advanced energy storage devices.

Polypyrrole Modified MoS2 Nanorod Composites as Durable Pseudocapacitive Anode Materials for Sodium-Ion Batteries

As a typical two-dimensional layered metal sulfide, MoS₂ has a high theoretical capacity and large layer spacing, which is beneficial for ion transport. Herein, a facile polymerization method is employed to synthesize polypyrrole (PPy) nanotubes, followed by a hydrothermal method to obtain flower-rod-shaped MoS₂/PPy (FR-MoS₂/PPy) composites. The FR-MoS₂/PPy achieves outstanding electrochemical performance as a sodium-ion battery anode. After 60 cycles under 100 mA g⁻¹, the FR-MoS₂/PPy can maintain a capacity of 431.9 mAh g⁻¹. As for rate performance, when the current densities range from 0.1 to 2 A g⁻¹, the capacities only reduce from 489.7 to 363.2 mAh g⁻¹. The excellent performance comes from a high specific surface area provided by the unique structure and the synergistic effect between the components. Additionally, the introduction of conductive PPy improves the conductivity of the material and the internal hollow structure relieves the volume expansion. In addition, kinetic calculations show that the composite material has a high sodium-ion transmission rate, and the external pseudocapacitance behavior can also significantly improve its electrochemical performance. This method provides a new idea for the development of advanced high-capacity anode materials for sodium-ion batteries.

A Lamellar Yolk-Shell Lithium-Sulfur Battery Cathode Displaying Ultralong Cycling Life, High Rate Performance, and Temperature Tolerance

The shuttling behavior and slow conversion kinetics of the intermediate lithium polysulfides are the severe obstacles for the application of lithium-sulfur (Li-S) batteries over a wide temperature range. Here, an engineered lamellar yolk-shell structure of In2 O3 @void@carbon for the Li-S battery cathode is developed for the first time to construct a powerful barrier that effectively inhibits the shuttling of polysulfides. On the basis of the unique nanochannel-containing morphology, the continuous kinetic transformation of sulfur and polysulfides is confined in a stable framework, which is demonstrated by using X-ray nanotomography. The constructed Li-S battery exhibits a high cycling capability over 1000 cycles at 1.0 C with a capacity decay rate as low as 0.038% per cycle, good rate performance, and temperature tolerance at -10, 25, and 50 °C. A nondestructive in situ monitoring method of the interfacial reaction resistance in different cycling stages is proposed, which provides a new analysis perspective for the development of emerging electrochemical energy-storage systems.

MoS2/PPy Nanocomposite as a Transducer for Electrochemical Aptasensor of Ampicillin in River Water

We report the design of an electrochemical aptasensor for ampicillin detection, which is an antibiotic widely used in agriculture and considered to be a water contaminant. We studied the transducing potential of nanostructure composed of MoS2 nanosheets and conductive polypyrrole nanoparticles (PPyNPs) cast on a screen-printed electrode. Fine chemistry is developed to build the biosensors entirely based on robust covalent immobilizations of naphthoquinone as a redox marker and the aptamer. The structural and morphological properties of the nanocomposite were studied by SEM, AFM, and FT-IR. High-resolution XPS measurements demonstrated the formation of a binding between the two nanomaterials and energy transfer affording the formation of heterostructure. Cyclic voltammetry and electrochemical impedance spectroscopy were used to analyze their electrocatalytic properties. We demonstrated that the nanocomposite formed with PPyNPs and MoS2 nanosheets has electro-catalytic properties and conductivity leading to a synergetic effect on the electrochemical redox process of the redox marker. Thus, a highly sensitive redox process was obtained that could follow the recognition process between the apatamer and the target. An amperometric variation of the naphthoquinone response was obtained regarding the ampicillin concentration with a limit of detection (LOD) of 10 pg/L (0.28 pM). A high selectivity towards other contaminants was demonstrated with this biosensor and the analysis of real river water samples without any treatment showed good recovery results thanks to the antifouling properties. This biosensor can be considered a promising device for the detection of antibiotics in the environment as a point-of-use system.

Polypyrrole-Based Metal Nanocomposite Electrode Materials for High-Performance Supercapacitors

Metallic nanostructures (MNs) and metal-organic frameworks (MOFs) play a pivotal role by articulating their significance in high-performance supercapacitors along with conducting polymers (CPs). The interaction and synergistic pseudocapacitive effect of MNs with CPs have contributed to enhance the specific capacitance and cyclic stability. Among various conjugated heterocyclic CPs, polypyrrole (PPy) (prevalently knows as “synthetic metal”) is exclusively studied because of its excellent physicochemical properties, ease of preparation, flexibility in surface modifications, and unique molecular structure–property relationships. Numerous researchers attempted to improve the low electronic conductivity of MNs and MOFs, by incorporating conducting PPy and/or used decoration strategy. This was succeeded by fine-tuning this objective, which managed to get outstanding supercapacitive performances. This brief technical note epitomizes various PPy-based metallic hybrid materials with different nano-architectures, emphasizing its technical implications in fabricating high-performance electrode material for supercapacitor applications.

Preparation of a polymer nanocomposite via the polymerization of pyrrole : biphenyldisulfonic acid : pyrrole as a two-monomer-connected precursor on MoS2 for electrochemical energy storage

We prepared a poly(pyrrole : biphenyldisulfonic acid : pyrrole (Py:BPDSA:Py)) nanocomposite of molybdenum disulfide (MoS₂), P(Py:BPDSA:Py)-MoS₂, with high crystallinity. The composite is synthesized by oxidative polymerization of Py:BPDSA:Py as a two-monomer-connected precursor (TMCP) linked by ionic bonding on a molybdenum disulfide (MoS₂) monolayer. The chemical, structural and morphological characterization of this composite is confirmed by Raman spectroscopy, FT-IR, X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and scanning electron microscopy (SEM). The crystal structure is analysed by X-ray diffraction (XRD) and high-voltage electron microscopy (HVEM), which shows a face-centered cubic (FCC) crystal structure for the composite. Nitrogen adsorption-desorption isotherms show an improved specific surface area (91.3 m² g^-1). The electrochemical properties of the composite with a unique crystal structure and a large specific surface area are analysed through cyclic voltammetry (CV), which shows a specific capacitance of 681 F g^-1 demonstrating that the composite can be used as an efficient electrode active material for electrochemical energy storage systems.

Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

Electrochemical properties of anthraquinone-containing polymer nanocomposite by nano-level molecular ordering

We prepared a novel redox polymer nanocomposite containing anthraquinione via polymerization of TMCP.

Two-dimensional β-MoO3@C nanosheets as high-performance negative materials for supercapacitors with excellent cycling stability

MoO₃ has gained a great deal of attention as a promising electrode material in energy storage devices. In particular, the low dimensional MoO₃ nanosheets coated with carbon layers are desirable electrode materials in supercapacitors. However, the fabrication or construction of β-MoO₃ with a special morphology is difficult. Here, we report a simple solvothermal treatment method to synthesize two-dimensional β-MoO₃@C (2D β-MoO₃@C) nanosheets. When used as electrode materials for supercapacitors, the as-prepared material displays an ultra-long lifespan with a 94% retention ratio after 50 000 cycles at 2 A g^-1. The excellent cycling stability is mainly attributed to the unique 2D nanosheet structure and the presence of the carbon layer on the surface of the nanosheet. Specifically, the presence of the carbon layer increases the electric conductivity of MoO₃, which facilitates a good access point for electrolyte ions and short ion diffusion paths. In addition, MoO₃ that has been coated with a carbon layer can maintain a good structural stability due to the carbon layer restricting the volume expansion of MoO₃ during the charge procedure. We believe that the present work opens a new way for designing the 2D layered materials with unique architectures for supercapacitor applications.

A low-cost paper-based flexible energy storage device using a conducting polymer nanocomposite

Herein, a simple approach is demonstrated for the fabrication of a paper-based flexible symmetrical supercapacitor as an energy saving device with composite functional materials of nickel nanoparticles (Ni NPs) and polypyrrole (PPy).

A polypyrrole-adorned, self-supported, pseudocapacitive zinc vanadium oxide nanoflower and nitrogen-doped reduced graphene oxide-based asymmetric supercapacitor device for power density applications

Herein, a distinctive approach has been implemented for exploiting a typical battery material zinc vanadium oxide (ZV) as a supercapacitor electrode material.

Hierarchical CoP@Ni2P core–shell nanosheets for ultrahigh energy density asymmetric supercapacitors

A Ni₂P nanosheet-modified ZIF-67-derived hierarchical CoP electrode was successfully fabricated on carbon paper with high electrochemical capacitance.

Synthesis of Double-Layer Nitrogen-Doped Microporous Hollow Carbon@MoS2/MoO2 Nanospheres for Supercapacitors

In this work, a double-layer nitrogen-doped microporous hollow carbon@MoS₂/MoO₂ nanosphere (NCs@MoS₂/MoO₂) is prepared via a facile method utilizing Mo-mediated in situ growth on polyaniline-coated polystyrene spheres and carbonization process. Because of its unique structure, the as-obtained NCs@MoS₂/MoO₂ exhibits a high specific capacitance (569 F g^-1 at 1 A g^-1) and excellent rate performance (54.8% capacitance retention) from 1 A g^-1 (569 F g^-1) to 20 A g^-1 (312 F g^-1) when directly used as a supercapacitor electrode. In a two-electrode system, it exhibits 81% capacitance retention and 91.4% Coulombic efficiency even after 5000 cycles at 5 A g^-1. Therefore, the prepared NCs@MoS₂/MoO₂ shows to be an outstanding material for supercapacitor electrodes.

A review of recent progress in molybdenum disulfide-based supercapacitors and batteries

This article reviews the recent progress in molybdenum disulfide-based supercapacitors and batteries.