Multifunctional Architectures Constructing of PANI Nanoneedle Arrays on MoS2 Thin Nanosheets for High-Energy Supercapacitors

Coal Tar Pitch-Based Porous Carbon Loaded MoS2 and Its Application in Supercapacitors

In this paper, with coal tar pitch as the carbon source, porous carbon (PC) was prepared by one-step carbonization. To improve the energy density of coal tar pitch-based porous carbon, MoS2@PC was prepared by a hydrothermal method on a PC substrate. The effect of MoS2 loading on the structure and electrochemical properties of the sample was studied. The results show that the specific surface area of the MoS2@PC-0.3 synthesized is 3053 m2 g-1, and the large specific surface area provides sufficient attachment sites for the storage of electrolyte ions. In the three-electrode system, the specific capacitance of MoS2@PC-0.3 at 0.5 A g-1 is 422.5 F g-1, and the magnification performance is 57.3% at 20 A g-1. After 10,000 charge/discharge cycles, the capacitance retention rate of the sample is 76.73%, with the Coulombic efficiency being 100%. In the two-electrode test system, the specific capacitance of MoS2@PC-0.3 at 0.5 A g-1 is 321.4 F g-1, with the power density and energy density being 500 W kg-1 and 44.6 Wh kg-1, respectively. At a current density of 20 A g-1, the capacitance retention rate is 87.69% after 10,000 cycles. This study greatly improves the energy density of PC as the electrode material of supercapacitors.

Molybdenum disulfide (MoS2) along with graphene nanoplatelets (GNPs) utilized to enhance the capacitance of conducting polymers (PANI and PPy)

Hybrid composites of molybdenum disulfide (MoS2), graphene nanoplatelets (GNPs) and polyaniline (PANI)/polypyrrole (PPy) have been synthesized as cost-effective electrode materials for supercapacitors. We have produced MoS2 from molybdenum dithiocarbamate by a melt method in an inert environment and then used a liquid exfoliation method to form its composite with graphene nanoplatelets (GNPs) and polymers (PANI and PPy). The MoS2 melt/GNP ratio in the resultant composites was 1 : 3 and the polymer was 10% by wt. of the original composite. XRD (X-ray diffraction analysis) confirmed the formation of MoS2 and SEM (scanning electron microscopy) revealed the morphology of the synthesized materials. The electrochemical charge storage performance of the synthesized composite materials was assessed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCCD) measurements. Resultant composites showed enhanced electrochemical performances (specific capacitance = 236.23 F g-1, energy density = 64.31 W h kg-1 and power density = 3858.42 W kg-1 for MoS2 melt 5 mPP at a current density of 0.57 A g-1 and had 91.87% capacitance retention after 10 000 charge-discharge cycles) as compared to the produced MoS2; thus, they can be utilized as electrode materials for supercapacitors.

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.

Recent Progress in Phase Regulation, Functionalization, and Biosensing Applications of Polyphase MoS2

The disulfide compounds of molybdenum (MoS₂ ) are layered van der Waals materials that exhibit a rich array of polymorphic structures. MoS₂ can be roughly divided into semiconductive phase and metallic phase according to the difference in electron filling state of the 4d orbital of Mo atom. The two phases show completely different properties, leading to their diverse applications in biosensors. But to some extent, they compensate for each other. This review first introduces the relationship between phase state and the chemical/physical structures and properties of MoS₂ . Furthermore, the synthetic methods are summarized and the preparation strategies for metastable phases are highlighted. In addition, examples of electronic and chemical property designs of MoS₂ by means of doping and surface modification are outlined. Finally, studies on biosensors based on MoS₂ in recent years are presented and classified, and the roles of MoS₂ with different phases are highlighted. This review offers references for the selection of materials to construct different types of biosensors based on MoS₂ , and provides inspiration for sensing performance enhancement.

Fabrication of one-dimensional M (Co, Ni)@polyaniline nanochains with adjustable thickness for excellent microwave absorption properties

The development of microwave absorbing materials with strong absorption capacity, wide bandwidth and light weight has always been a topic of concern. Herein, one-dimensional (1D) M (Co, Ni)@polyaniline (PANI) nanochains (NCs) with adjustable thickness have been successfully synthesized by reducing the mental ions under a parallel magnetic field, pretreating metal nanochains with KH550 and pre-oxidization of aniline monomer. It is found that Co has a more favorable absorption width for electromagnetic waves (EMW) and Ni aims at the absorption intensity. Furthermore, the effect of metal elements on adjusting impedance matching is more significant than their magnetic loss for composites. The minimum reflection loss (RLmin) of CoP2 can be up to -73.16 dB at 4.63 mm and the effective absorption bandwidth (EAB) is 4.98 GHz at 2.17 mm, while those of NiP2 are -65.06 dB at 3.88 mm and 5.02 GHz at 2.05 mm. The increase of PANI content can significantly reduce the matching thickness. And the RLmin of CoP3 and NiP3 can reach -58.72 dB at 2.32 mm and -65.96 dB at 1.59 mm, respectively. The absorption mechanism reveals that the matching thickness of the quarter-wavelength determines frequency location. And high absorption intensity is attributed to the synergistic effects of impedance matching, conduction loss, polarization loss, and magnetic loss. This work provides a theoretical basis for designing PANI or other conducting polymers coating magnetic nanochains for electromagnetic absorbing materials with strong absorption capacity, wide bandwidth and light weight.

Au-assisted polymerization of conductive poly(N-phenylglycine) as high-performance positive electrodes for asymmetric supercapacitors

Herein, a novel conductive poly(N-phenylglycine) (PNPG) polymer was successfully prepared, byin situelectrochemical polymerization method (+0.75 VversusAg/AgCl) for 10 min, on flexible stainless-steel plate coated with a thin Au film (Au/SS) to serve as a binder-free pseudocapacitive PNPG/Au/SS electrode for energy storage devices. Compared to the electrode without Au coating, PNPG/Au/SS electrode exhibited better electrochemical performance with larger specific capacitance (495 F g^-1at a current density of 2 A g^-1), higher rate performance and lower resistance, which are good indications to act as a positive electrode for asymmetric supercapacitor devices. Combined with activated carbon as a negative electrode, an asymmetric supercapacitor device was constructed. It displayed a specific capacitance of 38 F g^-1at a current density of 0.5 A g^-1and an energy density of 5.3 Wh kg^-1at a power density of 250 W kg^-1. Experimentally, two asymmetric supercapacitor devices were connected in series to power a home-made windmill continuously for 8 s, revealing the high potential of this novel conductive polymer material for energy storage application.

Nanoarchitectured Porous Conducting Polymers: From Controlled Synthesis to Advanced Applications

Conductive polymers (CPs) integrate the inherent characteristics of conventional polymers and the unique electrical properties of metals. They have aroused tremendous interest over the last decade owing to their high conductivity, robust and flexible properties, facile fabrication, and cost-effectiveness. Compared to bulk CPs, porous CPs with well-defined nano- or microstructures possess open porous architectures, high specific surface areas, more exposed reactive sites, and remarkably enhanced activities. These attractive features have led to their applications in sensors, energy storage and conversion devices, biomedical devices, and so on. In this review article, the different strategies for synthesizing porous CPs, including template-free and template-based methods, are summarized, and the importance of tuning the morphology and pore structure of porous CPs to optimize their functional performance is highlighted. Moreover, their representative applications (energy storage devices, sensors, biomedical devices, etc.) are also discussed. The review is concluded by discussing the current challenges and future development trend in this field.

Surface and Interface Engineering of Nanoarrays toward Advanced Electrodes and Electrochemical Energy Storage Devices

The overall performance of electrochemical energy storage devices (EESDs) is intrinsically correlated with surfaces and interfaces. As a promising electrode architecture, 3D nanoarrays (3D-NAs) possess relatively ordered, continuous, and fully exposed active surfaces of individual nanostructures, facilitating mass and electron transport within the electrode and charge transfer across interfaces and providing an ideal platform for engineering. Herein, a critical overview of the surface and interface engineering of 3D-NAs, from electrode and interface designs to device integration, is presented. The general merits of 3D-NAs and surface/interface engineering principles of 3D-NA hybrid electrodes are highlighted. The focus is on the use of 3D-NAs as a superior platform to regulate the interface nature and unveiling new mechanism/materials without the interference of binders. The engineering and utilization of the surface of 3D-NAs to develop flexible/solid-state EESDs with 3D integrated electrode/electrolyte interfaces, or 3D triphase interfaces involving other active species, which are characteristic of (quasi-)solid-state electrolyte infiltration into the entire device, are also considered. Finally, the challenges and future directions of surface/interface engineering of 3D-NAs are outlined. In particular, potential strategies to obtain electrode charge balance, optimize the multiphase solid-state interface, and attain 3D solid electrolyte infiltration are proposed.

In situ synthesis of polyaniline/carbon nanotube composites in a carbonized wood scaffold for high performance supercapacitors

Carbonized and activated wood scraps are appealing scaffolds upon which to host active materials for supercapacitors, realizing the transformation of waste into a valuable device. However, the active material when loaded on the inner walls of the wood tracheids can be easily peeled off, resulting in poor cycling stability of the capacitor and low energy density. Here, we designed a novel composite electrode material for high-performance supercapacitors based on a polyaniline/carbon nanotube composite material with a core-shell structure synthesized in situ in a carbonized wood scaffold. Carbon nanotubes with excellent conductivity were first synthesized in situ on the inner walls of the tracheids via chemical vapor deposition, which were stably embedded in the wood tracheids to increase the specific surface area and active material loading active sites. Then, a layer of polyaniline was deposited on the outer surface of each carbon nanotube via electrochemical deposition to form a core-shell nanostructure. The composite material as a single electrode has high specific capacitances of 240.0 F cm^-3 and 1019.5 F g^-1 at 10 mA cm^-2. Finally, the asymmetric supercapacitor based on the carbon nanotubes/carbonized wood scaffold as the anode and polyaniline/carbon nanotubes/carbonized wood scaffold as the cathode exhibited a high energy density of 40.5 W h kg^-1 at 162.5 W kg^-1 and a high capacity retention rate of 93.74% after 10 000 charge and discharge cycles at a current density of 20 mA cm^-2.

A covalently linked dual network structure achieved by rapid grafting of poly(p-phenylenediamine)-phosphomolybdic acid on reduced graphene oxide aerogel for improving the performance of supercapacitors

Covalent grafting of poly(p-phenylenediamine) (PPD)-phosphomolybdic acid (PMo₁₂) on rGO (PPD-PMo₁₂@rGO) has been realized within 1 minute. PPD-PMo₁₂@rGO shows a characteristic covalently linked dual network structure that can significantly enhance its specific capacitance and cycling stability for supercapacitor applications.

Layered Transition Metal Dichalcogenide-Based Nanomaterials for Electrochemical Energy Storage

The rapid development of electrochemical energy storage (EES) systems requires novel electrode materials with high performance. A typical 2D nanomaterial, layered transition metal dichalcogenides (TMDs) are regarded as promising materials used for EES systems due to their large specific surface areas and layer structures benefiting fast ion transport. The typical methods for the preparation of TMDs and TMD-based nanohybrids are first summarized. Then, in order to improve the electrochemical performance of various kinds of rechargeable batteries, such as lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, and other types of emerging batteries, the strategies for the design and fabrication of layered TMD-based electrode materials are discussed. Furthermore, the applications of layered TMD-based nanomaterials in supercapacitors, especially in untraditional supercapacitors, are presented. Finally, the existing challenges and promising future research directions in this field are proposed.

A binder-free Ni2P2O7/Co2P2O7 nanograss array as an efficient cathode for supercapacitors

Binder-free Ni₂P₂O₇/Co₂P₂O₇ cathode of nanograss morphology, delivered an energy and power density of 33.2 W h kg⁻¹ and 257.8 W kg⁻¹ respectively. Through power law, the contribution of each type of mechanism in charge storage process was calculated.

Few-Layer MoS2 Nanosheets Encapsulated in N-Doped Carbon Hollow Spheres as Long-Life Anode Materials for Lithium-Ion Batteries

Two-dimensional molybdenum disulfide (MoS₂ ) has been recognized as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity, but its rapid capacity decay owing to poor conductivity, structure pulverization, and polysulfide dissolution presents significant challenges in practical applications. Herein, triple-layered hollow spheres in which MoS₂ nanosheets are fully encapsulated between inner carbon and outer nitrogen-doped carbon (NC) were fabricated. Such an architecture provides high conductivity and efficient lithium-ion transfer. Moreover, the NC shell prevents aggregation and exfoliation of MoS₂ nanosheets and thus maintains the integrity of the nanostructure during the charge/discharge process. As anode materials for LIBs, the C@MoS₂ @NC hollow spheres deliver a high reversible capacity (747 mA h g^-1 after 100 cycles at 100 mA g^-1 ) and excellent long-cycle performance (650 mA h g^-1 after 1000 cycles at 1.0 A g^-1 ), which confirm its potential for high-performance LIBs.

Synthesis and Electrochemical Energy Storage Applications of Micro/Nanostructured Spherical Materials

Micro/nanostructured spherical materials have been widely explored for electrochemical energy storage due to their exceptional properties, which have also been summarized based on electrode type and material composition. The increased complexity of spherical structures has increased the feasibility of modulating their properties, thereby improving their performance compared with simple spherical structures. This paper comprehensively reviews the synthesis and electrochemical energy storage applications of micro/nanostructured spherical materials. After a brief classification, the concepts and syntheses of micro/nanostructured spherical materials are described in detail, which include hollow, core-shelled, yolk-shelled, double-shelled, and multi-shelled spheres. We then introduce strategies classified into hard-, soft-, and self-templating methods for synthesis of these spherical structures, and also include the concepts of synthetic methodologies. Thereafter, we discuss their applications as electrode materials for lithium-ion batteries and supercapacitors, and sulfur hosts for lithium–sulfur batteries. The superiority of multi-shelled hollow micro/nanospheres for electrochemical energy storage applications is particularly summarized. Subsequently, we conclude this review by presenting the challenges, development, highlights, and future directions of the micro/nanostructured spherical materials for electrochemical energy storage.

Iron oxide-based nanomaterials for supercapacitors

As highly efficient and clean electrochemical energy storage devices, supercapacitors (SCs) have drawn widespread attention as promising alternatives to batteries in recent years. Among various electrode materials, iron oxide materials have been widely studied as negative SC electrode materials due to their broad working window in negative potential, ideal theoretical specific capacitance, good redox activity, abundant availability, and eco-friendliness. However, iron oxides still suffer from the problems of low stability and poor conductivity. In this review, recent progress in iron oxide-based nanomaterials, including Fe₂O₃, Fe₃O₄, Fe_xO_y, and FeOOH, as electrode materials of SCs, is discussed. The nanostructure design and various synergistic effects of nanocomposites for improving the electrochemical performance of iron oxides are emphasized. Research on iron oxide-based symmetric/asymmetric SCs is also discussed. Future outlooks regarding iron oxides for SCs are likewise proposed.

Application of Polyaniline for Li-Ion Batteries, Lithium-Sulfur Batteries, and Supercapacitors

Conducting polyaniline (PANI) exhibits interesting properties, such as high conductivity, reversible convertibility between redox states, and advantageous structural feature. It therefore receives ever-increasing attention for various applications. This Minireview evaluates recent studies on application of PANI for Li-ion batteries (LIBs), Li-S batteries (LSBs) and supercapacitors (SCPs). The flexible PANI is crucial for cyclability, especially for buffering the volumetric changes of electrode materials, in addition to enhancing the electron/ion transport. Furthermore, PANI can be directly used as an electroactive component in electrode materials for LIBs or SCPs and can be widely applied in LSBs due to its physically and chemically strong affinity for S and polysulfides. The evaluation of studies herein reveals significant improvements of electrochemical performance by physical/chemical modification and incorporation of PANI.

Phosphorus-Mediated MoS2 Nanowires as a High-Performance Electrode Material for Quasi-Solid-State Sodium-Ion Intercalation Supercapacitors

Molybdenum disulfide (MoS₂ ) is a promising electrode material for electrochemical energy storage owing to its high theoretical specific capacity and fascinating 2D layered structure. However, its sluggish kinetics for ionic diffusion and charge transfer limits its practical applications. Here, a promising strategy is reported for enhancing the Na⁺ -ion charge storage kinetics of MoS₂ for supercapacitors. In this strategy, electrical conductivity is enhanced and the diffusion barrier of Na⁺ ion is lowered by a facile phosphorus-doping treatment. Density functional theory results reveal that the lowest energy barrier of dilute Na-vacancy diffusion on P-doped MoS₂ (0.11 eV) is considerably lower than that on pure MoS₂ (0.19 eV), thereby signifying a prominent rate performance at high Na intercalation stages upon P-doping. Moreover, the Na-vacancy diffusion coefficient of the P-doped MoS₂ at room temperatures can be enhanced substantially by approximately two orders of magnitude (10^-6 -10^-4 cm² s^-1 ) compared with pure MoS₂ . Finally, the quasi-solid-state asymmetrical supercapacitor assembled with P-doped MoS₂ and MnO₂ , as the positive and negative electrode materials, respectively, exhibits an ultrahigh energy density of 67.4 W h kg^-1 at 850 W kg^-1 and excellent cycling stability with 93.4% capacitance retention after 5000 cycles at 8 A g^-1 .

Graphene-like MoS2 Nanosheets on Carbon Fabrics as High-Performance Binder-free Electrodes for Supercapacitors and Li-Ion Batteries

Two-dimensional layer-structure materials are now of great interest in energy storage devices, owing to their graphene-like structure and high theoretical capacity. Herein, graphene-like molybdenum disulfide (MoS₂) nanosheets were uniformly grown on carbon fabrics by using a hydrothermal method. They were evaluated as binder-free electrodes for Li-ion batteries (LIBs) and supercapacitors. As expected, long cycling life and high capacity/capacitance are achieved. When used as self-standing electrodes for LIBs, they deliver a high area capacity of ∼0.5 mAh/cm² even after 400 cycles and remarkable rate capability in the charge/discharge potential range of 1-3 V. In addition, a three-dimensional integrated electrode of the MoS₂ nanosheet exhibits a high capacitance of 103.5 mF/cm² and long cycling stability up to at least 15 000 cycles at a current density of 3 mA/cm² for supercapacitors. The great cycling stability of MoS₂ in supercapacitors is promising in the enhancement of cycling stability through their integration with other materials as alternatives to graphene in some special fields.

Metallic MoS2 for High Performance Energy Storage and Energy Conversion

Metallic phase 2D molybdenum disulfide (MoS₂ ) is an emerging class of materials with remarkably higher electrical conductivity and catalytic activities. The goal of this study is to review the atomic structures and electrochemistry of metallic MoS₂ , which is essential for a wide range of existing and new enabling technologies. The scope of this paper ranges from the atomic structure, band structure, electrical and optical properties to fabrication methods, and major emerging applications in electrochemical energy storage and energy conversion. This paper also thoroughly covers the atomic structure-properties-application relationships of metallic MoS₂ . Understanding the fundamental properties of these structures is crucial for designing and manufacturing products for emerging applications. Today, a more holistic understanding of the interplay between the structure, chemistry, and performance of metallic MoS₂ is advancing actual applications of this material. This new level of understanding also enables a myriad of new and exciting applications, which motivated this review. There are excellent reviews already on the traditional semiconducting MoS₂ , and this review, for the first time, focuses on the uniqueness of conducting metallic MoS₂ for energy applications and offers brand new materials for clean energy application.

MoS2 /MoOx -Nanostructure-Decorated Activated Carbon Cloth for Enhanced Supercapacitor Performance

MoS₂ /MoO_x nanostructures were grown on activated carbon cloth through a facile one-step microwave-assisted hydrothermal method. The growth of MoS₂ /MoO_x on activated carbon cloth creates a unique structure that favors ion intercalation. The conductive activated carbon cloth, MoO_3-x , and monoclinic MoO₂ provide fast electron transport, whereas the MoS₂ nanosheets/MoO_3-x nanoparticles structure improves the capacitance. As a result, MoS₂ /MoO_x -nanostructure-decorated activated carbon cloth shows a high specific capacitance of 230 F g^-1 at a scan rate of 5 mV s^-1 with a low contact resistance of approximately 1.91 Ω. Moreover, the activated carbon cloth acts as a template for the growth of a perpendicular MoS₂ layer, which gives an excellent utilization rate of the active MoS₂ /MoO_x material. We also demonstrate that the MoS₂ /MoO_x /activated carbon cloth nanocomposite shows excellent electrochemical stability with retention up to 128 % after 1500 cycles. Finally, we show the use of a microwave-assisted hydrothermal method for the synthesis of the MoS₂ /MoO_x /activated carbon cloth nanocomposite as an alternative and clean route to improve the kinetics of the intercalation redox reaction.

Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives

Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS₂, MoSe₂, MoTe₂, WS₂ and WSe₂, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.

Use of a diatomite template to prepare a MoS2/amorphous carbon composite and exploration of its electrochemical properties as a supercapacitor

Amorphous carbon is partially inserted into the interlayer spaces of MoS₂ in the composite prepared using a template method.

1D Nanomaterials: Design, Synthesis, and Applications in Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have received extensive attention as ideal candidates for large-scale energy storage systems (ESSs) owing to the rich resources and low cost of sodium (Na). However, the larger size of Na⁺ and the less negative redox potential of Na⁺ /Na result in low energy densities, short cycling life, and the sluggish kinetics of SIBs. Therefore, it is necessary to develop appropriate Na storage electrode materials with the capability to host larger Na⁺ and fast ion diffusion kinetics. 1D materials such as nanofibers, nanotubes, nanorods, and nanowires, are generally considered to be high-capacity and stable electrode materials, due to their uniform structure, orientated electronic and ionic transport, and strong tolerance to stress change. Here, the synthesis of 1D nanomaterials and their applications in SIBs are reviewed. In addition, the prospects of 1D nanomaterials on energy conversion and storage as well as the development and application orientation of SIBs are presented.

Novel ternary nanocomposites of MWCNTs/PANI/MoS2: preparation, characterization and enhanced electrochemical capacitance

In this work, nanoflower-like MoS₂ grown on the surface of multi-walled carbon nanotubes (MWCNTs)/polyaniline (PANI) nano-stem is synthesized via a facile in situ polymerization and hydrothermal method. Such a novel hierarchical structure commendably promotes the contact of PANI and electrolyte for faradaic energy storage. In the meanwhile, the double-layer capacitance of MoS₂ is effectively used. The morphology and chemical composition of the as-prepared samples are characterized by scanning and transmission electron microscopies, X-ray diffraction and Fourier transform infrared spectra. The electrochemical performance of the samples is evaluated by cyclic voltammogram and galvanostatic charge-discharge measurements. It is found that the specific capacitance of the obtained MWCNTs/PANI/MoS₂ hybrid is 542.56 F g^-1 at a current density of 0.5 A g^-1. Furthermore, the MWCNTs/PANI/MoS₂ hybrid also exhibits good rate capability (62.5% capacity retention at 10 A g^-1) and excellent cycling stability (73.71% capacitance retention) over 3000 cycles.

Growth of 2D Mesoporous Polyaniline with Controlled Pore Structures on Ultrathin MoS2 Nanosheets by Block Copolymer Self-Assembly in Solution

The development of versatile strategies toward two-dimensional (2D) porous nanocomposites with tunable pore structures draws immense scientific attention in view of their attractive physiochemical properties and a wide range of promising applications. This paper describes a self-assembly approach for the directed growth of mesoporous polyaniline (PANi) with tunable pore structures and sizes on ultrathin freestanding MoS₂ nanosheets in solution, which produces 2D mesoporous PANi/MoS₂ nanocomposites. The strategy employs spherical and cylindrical micelles, which are formed by the controlled solution self-assembly of block copolymers, as the soft templates for the construction of well-defined spherical and cylindrical mesopores in the 2D PANi/MoS₂ nanocomposites, respectively. With potential applications as supercapacitor electrode materials, the resultant 2D composites show excellent capacitive performance with a maximum capacitance of 500 F g^-1 at a current density of 0.5 A g^-1, good rate performance, as well as outstanding stability for charge-discharge cycling. Moreover, the 2D mesoporous nanocomposites offer an opportunity for the study on the influence of different pore structures on their capacitive performance, which helps to understand the pore structure-property relationship of 2D porous electrode materials and to achieve their electrochemical performance control.

Stretchable Electronic Sensors of Nanocomposite Network Films for Ultrasensitive Chemical Vapor Sensing

A stretchable, transparent, and body-attachable chemical sensor is assembled from the stretchable nanocomposite network film for ultrasensitive chemical vapor sensing. The stretchable nanocomposite network film is fabricated by in situ preparation of polyaniline/MoS₂ (PANI/MoS₂ ) nanocomposite in MoS₂ suspension and simultaneously nanocomposite deposition onto prestrain elastomeric polydimethylsiloxane substrate. The assembled stretchable electronic sensor demonstrates ultrasensitive sensing performance as low as 50 ppb, robust sensing stability, and reliable stretchability for high-performance chemical vapor sensing. The ultrasensitive sensing performance of the stretchable electronic sensors could be ascribed to the synergistic sensing advantages of MoS₂ and PANI, higher specific surface area, the reliable sensing channels of interconnected network, and the effectively exposed sensing materials. It is expected to hold great promise for assembling various flexible stretchable chemical vapor sensors with ultrasensitive sensing performance, superior sensing stability, reliable stretchability, and robust portability to be potentially integrated into wearable electronics for real-time monitoring of environment safety and human healthcare.