Core-shell composite of hierarchical MoS2 nanosheets supported on graphitized hollow carbon microspheres for high performance lithium-ion batteries

Ammonium-driven modulation of 1T-MoS2 structure and composite with graphene: A pathway to high-performance lithium-ion battery anodes

The lack of stable anode materials with high capacity and fast redox kinetics has hindered the application of lithium-ion batteries (LIBs) for energy storage. Metal-phase molybdenum disulfide (1T-MoS2) is recognized as a promising energy storage material because of its combination of excellent physical and electrochemical properties. In this paper, we report the insertion of ammonium ions (NH4+) into the MoS2 interlayer and effective complexation with graphene oxide (GO). The MoS2 layer spacing was effectively enlarged from 0.67 nm to 1.1 nm by NH4+ insertion, and this method not only maintains the stability of the 1T phase and reduces the energy barriers for Li+ insertion and de-embedding, but also improves the diffusion kinetics of Li+. The Li+ diffusion coefficients of the prepared 1T-MoS2/G composites were confirmed to be enhanced by three orders of magnitude by constant current intermittent titration technique tests. Compared with the conventional preparation method, the mechanism of action of NH4+ insertion provides a new regulation strategy. In addition, electrochemical studies showed that the specific capacity of the prepared 1T-MoS2/G electrode was 1533 mAh/g for 180 cycles at 0.1 A/g and 1679 mAh/g for 800 cycles at 0.5 A/g. Thus, the strategy of introducing NH4+ intercalation to improve the cycling stability of MoS2 raises the prospect of practical application of layered metal sulfide anodes.

Phase Engineering of Nanomaterials: Transition Metal Dichalcogenides

Crystal phase, a critical structural characteristic beyond the morphology, size, dimension, facet, etc., determines the physicochemical properties of nanomaterials. As a group of layered nanomaterials with polymorphs, transition metal dichalcogenides (TMDs) have attracted intensive research attention due to their phase-dependent properties. Therefore, great efforts have been devoted to the phase engineering of TMDs to synthesize TMDs with controlled phases, especially unconventional/metastable phases, for various applications in electronics, optoelectronics, catalysis, biomedicine, energy storage and conversion, and ferroelectrics. Considering the significant progress in the synthesis and applications of TMDs, we believe that a comprehensive review on the phase engineering of TMDs is critical to promote their fundamental studies and practical applications. This Review aims to provide a comprehensive introduction and discussion on the crystal structures, synthetic strategies, and phase-dependent properties and applications of TMDs. Finally, our perspectives on the challenges and opportunities in phase engineering of TMDs will also be discussed.

Recent progress in MoS2 nanostructures for biomedical applications: Experimental and computational approach

In the category of 2D materials, MoS2 a transition metal dichalcogenide, is a novel and intriguing class of materials with interesting physicochemical properties, explored in applications ranging from cutting-edge optoelectronic to the frontiers of biomedical and biotechnology. MoS2 nanostructures an alternative to heavy toxic metals exhibit biocompatibility, low toxicity and high stability, and high binding affinity to biomolecules. MoS2 nanostructures provide a lot of opportunities for the advancement of novel biosensing, nanodrug delivery system, electrochemical detection, bioimaging, and photothermal therapy. Much efforts have been made in recent years to improve their physiochemical properties by developing a better synthesis approach, surface functionalization, and biocompatibility for their safe use in the advancement of biomedical applications. The understanding of parameters involved during the development of nanostructures for their safe utilization in biomedical applications has been discussed. Computational studies are included in this article to understand better the properties of MoS2 and the mechanism involved in their interaction with biomolecules. As a result, we anticipate that this combined experimental and computational studies of MoS2 will inspire the development of nanostructures with smart drug delivery systems, and add value to the understanding of two-dimensional smart nano-carriers.

One-Pot Hydrothermal Synthesis of Solution-Processable MoS2/PEDOT:PSS Composites for High-Performance Supercapacitors

It is challenging to hydrothermally synthesize solution-processable MoS₂, as the strong van der Waals force between MoS₂ nanosheets induces self-assembly of agglomerates. Here, we introduce poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) into the precursor to impede aggregate formation in the hydrothermal process. A hybrid MoS₂/PEDOT:PSS (MP) hydrogel is formed due to the electrostatic interactions between the negatively charged MoS₂ and positively charged PEDOT chains. This hydrogel can be easily dispersed in water for subsequent solution processing such as vacuum filtration to form free-standing flexible films or extrusion 3D printing to create novel patterns. The MP film with a fracture strength of 18.59 MPa displays excellent electrochemical performance in both aqueous Na₂SO₄ electrolyte (474 mF cm^-2) and solid-state PVA-H₃PO₄ electrolyte (360 mF cm^-2). Flexibility and robustness can be evidenced by high capacitance retention rates of 94 and 89% after being repeatedly bent to 180° for 5000 cycles in aqueous and solid-state electrolytes, respectively.

Highly pseudocapacitive metal-organic framework derived carbon skeleton supported Fe-Ti-O nanotablets as an anode material for efficient lithium storage

A facile and effective method to fabricate highly pseudocapacitive electrodes of Fe-Ti-O@C has been proposed here. In this strategy, FeOOH crystals were firstly grown uniformly on the surface of Ti-based MOF (MIL-125) tablet substrates through a solution immersion method, and then converted to uniform carbon supported Fe-Ti-O composites by calcination under argon. The obtained Fe-Ti-O@C composites were first utilized as an efficient anode for lithium ion batteries with a high reversible capacity of 988 mA h g^-1 after 160 cycles at 200 mA g^-1. Such a superior lithium storage performance may be due to the synergistic effect of the Fe₃O₄ nanoparticles with a high capacity, FeTiO₃ nanocomposites with a nearly stable structure during the Li⁺ insertion/removal process, and the conductive carbon skeleton with a large surface area and porous structure. This work represents an important step forward in the fabrication of MOF-derived hybrids and enables transition metal oxides (TMOs) to have potential applications in energy storage systems.

Recent progress of TMD nanomaterials: phase transitions and applications

Transition metal dichalcogenides (TMDs) show wide ranges of electronic properties ranging from semiconducting, semi-metallic to metallic due to their remarkable structural differences. To obtain 2D TMDs with specific properties, it is extremely important to develop particular strategies to obtain specific phase structures. Phase engineering is a traditional method to achieve transformation from one phase to another controllably. Control of such transformations enables the control of properties and access to a range of properties, otherwise inaccessible. Then extraordinary structural, electronic and optical properties lead to a broad range of potential applications. In this review, we introduce the various electronic properties of 2D TMDs and their polymorphs, and strategies and mechanisms for phase transitions, and phase transition kinetics. Moreover, the potential applications of 2D TMDs in energy storage and conversion, including electro/photocatalysts, batteries/supercapacitors and electronic devices, are also discussed. Finally, opportunities and challenges are highlighted. This review may further promote the development of TMD phase engineering and shed light on other two-dimensional materials of fundamental interest and with potential ranges of applications.

Design of Ni(OH)2 nanocages@MnO2 nanosheets core-shell architecture to jointly facilitate electrocatalytic dynamic for highly sensitive detection of dopamine

In this work, Ni(OH)₂ nanocages@MnO₂ nanosheets core-shell architecture (Ni(OH)₂ NCs@MnO₂ NSs CSA) was successfully prepared through coordinated etching and precipitation (CEP) route followed by hydrothermal reaction, and then tested as sensitive electrode material for detection of dopamine (DA). The three dimensional (3D) hollow Ni(OH)₂ core effectively prevented the aggregation of MnO₂ NSs, leading to high utilization rate of MnO₂ NSs. Meanwhile, the two dimensional (2D) MnO₂ shell endowed Ni(OH)₂ NCs with larger specific area and abundant diffusion channels, facilitating mass transport. Ni(OH)₂ NCs@MnO₂ NSs CSA modified glassy carbon electrode (GCE) exhibited two satisfying sensitivities of 467.1 and 1249.9 μA mM^-1 cm^-2 within the two linear ranges of 0.02-16.30 μM and 18.30-118.58 μM, respectively. Furthermore, Ni(OH)₂ NCs@MnO₂ NSs CSA/GCE presented low detection limit of 1.75 nM and short response time of 1.14 s. Overall, Ni(OH)₂ NCs@MnO₂ NSs/GCE looks promising for analytical sensing of DA thanks to its prominent electrocatalytic dynamic issued from the 3D hollow structure@2D nanosheets core-shell architecture.

A Composite Photocatalyst Based on Hydrothermally-Synthesized Cu₂ZnSnS₄ Powders

A novel composite photocatalyst based on Cu₂ZnSnS₄ (CZTS) powders was synthesized and investigated for use as a photocatalyst. CZTS powders were first made using a conventional hydrothermal method and were then used to grow silver nanoparticles hybridized onto the CZTS under various conditions through a microwave-assisted hydrothermal process. After the obtained samples were subsequently mixed with 1T-2H MoS₂, the three synthesized component samples were characterized using X-ray diffractometry (XRD), scanning electron microscopy, transmission electron microscopy (FE-SEM, FE-TEM), UV-visible spectroscopy (UV-Vis), Brunauer-Emmet-Teller (BET), photoluminescence spectroscopy (PL), and X-ray photoelectron spectroscopy (XPS). The resulting samples were also used as photocatalysts for the degradation of methylene blue (MB) under a 300 W halogen lamp simulating sunlight with ~5% UV light. The photodegradation ability was greatly enhanced by the addition of Ag and 1T-2H MoS₂. Excellent photodegradation of MB was obtained under visible light. The effects of material characteristics on the photodegradation were investigated and discussed.

Towards thermally stable high performance lithium-ion batteries: the combination of a phosphonium cation ionic liquid and a 3D porous molybdenum disulfide/graphene electrode

A lithium battery with excellent performance and thermal stability is realized by using a nanostructured electrode and an ionic liquid.

Petal-like MoS2 Nanosheets Space-Confined in Hollow Mesoporous Carbon Spheres for Enhanced Lithium Storage Performance

An innovative approach for efficient synthesis of petal-like molybdenum disulfide nanosheets inside hollow mesoporous carbon spheres (HMCSs), the yolk-shell structured MoS₂@C, has been developed. HMCSs effectively control and confine in situ growth of MoS₂ nanosheets and significantly improve the conductivity and structural stability of the hybrid material. The yolk-shell structured MoS₂@C is proven to achieve high reversible capacity (993 mA h g^-1 at 1 A g^-1 after 200 cycles), superior rate capability (595 mA h g^-1 at a current density of 10 A g^-1), and excellent cycle performance (962 mA h g^-1 at 1 A g^-1 after 1000 cycles and 624 mA h g^-1 at 5 A g^-1 after 400 cycles) when evaluated as an anode material for lithium-ion batteries. This superior performance is attributed to the yolk-shell structure with conductive mesoporous carbon as the shell and the stack of two-dimensional MoS₂ nanosheets as the yolk.

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.

Graphene-wrapped CNT@MoS2hierarchical structure: synthesis, characterization and electrochemical application in supercapacitors

A hierarchical, tubular “sandwich” structure composed of graphene-wrapped CNT@MoS₂has been fabricated and applied as an electrode material for supercapacitors.