Rhombohedrally stacked layered transition metal dichalcogenides and their electrocatalytic applications

Layered transition metal dichalcogenides (TMDCs) are extensively investigated as catalyst materials for a wide range of electrochemical applications due to their high surface area and versatile electronic and chemical properties. Bulk TMDCs are van der Waals solids that possess strong in-plane bonding and weak inter-layer interactions. In the few-layer 2D TMDCs, several polymorphic structures have been reported as each individual layer can either retain octahedral or trigonal prismatic coordination. Among them, 1T (tetragonal), 2H (hexagonal) and 3R (rhombohedral) phases are very common. These polymorphs can display discrepancies in their catalytic activity as their electronic structure diverges due to different d orbital filling states. The broken inversion symmetry and large exposed edge sites of some of the 3R-phase TMDCS such as MoS2, NbS2 and TaS2 appear to be advantageous for electrocatalytic water reduction and battery applications. We describe recent studies in phase engineering of 2D TMDCs, particularly aiming at the 3R polytype and their electrocatalytic properties. Redox ability primarily depends on a distinct polymorphic phase in which TMDCs are isolated, and hence, with rich polymorphic structures being reported, numerous new catalytic applications can be realized. Phase conversion from 2H to 3R phase in some TMDCs enhances structural integrity and establishes robustness under harsh chemical conditions.

Synergistic interaction between molybdenum disulfide nanosheet and metal organic framework for high performance supercapacitor.. [DOI: 10.21203/rs.3.rs-3263864/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Zeolitic imidazolate framework-67 crystals (ZIF-67) anchored molybdenum disulfide nanosheets (MS) have been synthesized via a hydrothermal approach followed by a simple chemical method. MS concentration has been varied to investigate its impact on the electrochemical efficiency within the electrode nanocomposite. The shiny spot of this composite is the combination of two desirable properties, the conductive path created by MS, and the structural framework support provided by Zeolitic imidazolate framework-67 intercalated with nickel (Z67.Ni). The reason behind this choice of this specific nanocomposite is the framework of the Z67.Ni that prevents MS nanosheets from restacking during the repeated charge and discharge cycles. Superior electrochemical behavior of Z67.Ni with 70% weight percent of MS (Z67.Ni/MS7) demonstrated the excellent synergistic effect between Z67.Ni crystals and MS nanosheets. It has a specific capacitance of 308.5 F g− 1 at 1 A g− 1 and delivers an excellent energy density (Ed) of 83.98 W h kg− 1 with a power density (Pd) of 2.78 kW kg− 1. These excellent results demonstrate the high efficiency of this nanocomposite material in supercapacitor applications.

In Situ Synthesis of Crystalline MoS2@ZIF-67 Nanocomposite for the Efficient Removal of Methyl Orange Dye from Aqueous Media

The zeolitic imidazolate framework-67 (ZIF-67) adsorbent and its composites are known to effectively remove organic dyes from aqueous environments. Here, we report a unique crystalline MoS2@ZIF-67 nanocomposite adsorbent for the efficient removal of methyl orange (MO) dye from an aqueous medium. In situ synthetic techniques were used to fabricate a well-crystalline MoS2@ZIF-67 nanocomposite, which was then discovered to be a superior adsorbent to its constituents. The successful synthesis of the nanocomposite was confirmed using XRD, EDX, FTIR, and SEM. The MoS2@ZIF-67 nanocomposite exhibited faster adsorption kinetics and higher dye removal efficiency compared with its constituents. The adsorption kinetic data matched well with the pseudo-second-order model, which signifies that the MO adsorption on the nanocomposite is a chemically driven process. The Langmuir model successfully illustrated the MO dye adsorption on the nanocomposite through comparing the real data with adsorption isotherm models. However, it appears that the Freundlich adsorption isotherm model was also in competition with the Langmuir model. According to the acquired thermodynamics parameters, the adsorption of MO on the MoS2@ZIF-67 nanocomposite surface was determined to be spontaneous and exothermic. The findings of this research open an avenue for using the MoS2@ZIF-67 nanocomposite to efficiently remove organic dyes from wastewater efflux.

Designing Hybrid Mesoporous Pr/Tannate-Inbuilt ZIF8-Decorated MoS2 as Novel Nanoreservoirs toward Smart pH-Triggered Anti-corrosion/Robust Thermomechanical Epoxy Nanocoatings

For the first time, organic tannic acid (TA) molecules and then inorganic praseodymium (Pr) cations as corrosion inhibitors were successfully loaded into a zeolitic imidazolate framework (ZIF8)-type porous coordination polymer (PCP) decorated on molybdenum disulfide, MoS₂, (MS)-based transition metal dichalcogenides (TMDs) to create novel hybrid mesoporous Pr/TA-ZIF8@MS nanoreservoirs. Thereafter, the hybrid nanoreservoirs were embedded into the epoxy matrix for the preparation of smart pH-triggered nanocoatings. Characterizations of the Pr/TA-ZIF8@MS nanoreservoirs via Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric (TG), Brunauer-Emmett-Teller (BET), and field emission-scanning electron microscopy (FE-SEM)/energy-dispersive X-ray spectroscopy (EDS) experiments confirmed the fabrication of mesoporous structures comprising Pr/TA interfacial interactions with ZIF8-decorated MS nanoplatelets possessing high thermal stability and compact/dense configuration features with a framework reorientation. A remarkable smart release of the inhibited cations (Pr³⁺ and Zn²⁺) in the presence of inbuilt TA at both acidic and alkaline media was achieved under inductively coupled plasma (ICP) examination. The superior pH-triggered self-healing inhibition through the smart controlled-release of Pr, tannate, Zn, and imidazole inhibited species/complexes from EP/Pr-TA-ZIF8@MS via ligand exchange was obtained from electrochemical impedance spectroscopy (EIS) assessments of the scratched coatings during 72 h of saline immersion. In addition, the long-term barrier-induced corrosion prevention (log |Z|_10 mHz = 10.49 Ω·cm² after 63 days) of the EP/Pr-TA-ZIF8@MS was actualized. Moreover, efficient increments of the coating cross-link density (56.45%), tensile strength (63.6%), and toughness value (56.5%) compared to the Neat epoxy coating revealed noticeable thermomechanical properties of the EP/Pr-TA-ZIF8@MS.

Coordination-Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

2D materials have received tremendous scientific and engineering interests due to their remarkable properties and broad-ranging applications such as energy storage and conversion, catalysis, biomedicine, electronics, and so forth. To further enhance their performance and endow them with new functions, 2D materials are proposed to hybridize with other nanostructured building blocks, resulting in hybrid nanostructures with various morphologies and structures. The properties and functions of these hybrid nanostructures depend strongly on the interfacial interactions between 2D materials and other building blocks. Covalent and coordination bonds are two strong interactions that hold high potential in constructing these robust hybrid nanostructures based on 2D materials. However, most 2D materials are chemically inert, posing problems for the covalent assembly with other building blocks. There are usually coordination atoms in most of 2D materials and their derivatives, thus coordination interaction as a strong interfacial interaction has attracted much attention. In this review, recent progress on the coordination-driven hierarchical assembly based on 2D materials is summarized, focusing on the synthesis approaches, various architectures, and structure-property relationship. Furthermore, insights into the present challenges and future research directions are also presented.

Challenges and recent advancements of functionalization of two-dimensional nanostructured molybdenum trioxide and dichalcogenides

Atomically thin two-dimensional (2D) semiconductors are the thinnest functional semiconducting materials available today. Among them, both molybdenum trioxide and chalcogenides (MT&Ds) represent key components within the family of different 2D semiconductors for various electronic, optoelectronic and electrochemical applications due to their unique electronic, optical, mechanical and electrochemical properties. However, despite great progress in research dedicated to the development and fabrication of 2D MT&Ds observed within the last decade, there are significant challenges that affected their charge transport behavior and fabrication on a large scale as well as there is high dependence of the carrier mobility on the thickness. In this article, we review the recent progress in the carrier mobility engineering of 2D MT&Ds and elaborate devised strategies dedicated to the optimization of MT&D properties. Specifically, the latest physical and chemical methods towards the surface functionalization and optimization of the major factors influencing the extrinsic transport at the electrode-2D semiconductor interface are discussed.

Polyoxometalate@MIL-101/MoS2: a composite material based on the MIL-101 platform with enhanced performances

MIL-101 was used as a platform to integrate two functional materials for achieving enhanced dye adsorption and separation performances.

A covalently conjugated MoS2/Fe3O4 magnetic nanocomposite as an efficient & reusable catalyst for H2 production

Quick and easy recovery without the loss of the photocatalytic activity of the catalysing agent is an effective way to meet the challenges associated with the high cost of hazard-free hydrogen production. A '2D/0D' covalently conjugated nanocomposite of MoS₂/Fe₃O₄ has shown efficient catalyzing ability for five cycles of dye-sensitized H₂ evolution.

The synthesis of ZnS@MoS2 hollow polyhedrons for enhanced lithium storage performance

ZnS@MoS₂ hollow polyhedrons display outstanding cycling performance and high reversible specific capacity in LIB anodes.

Synthesis, characterization, surface properties and energy device characterstics of 2D borocarbonitrides, (BN)xC1−x, covalently cross-linked with sheets of other 2D materials

Covalent cross-linking of 2D structures such as graphene, MoS₂ and C₃N₄ using coupling reactions affords the generation of novel materials with new or improved properties. These covalently cross-linked structures provide the counter point to the van der Waals heterostructures, with an entirely different set of features and potential applications. In this article, we describe the materials obtained by bonding borocarbonitride (BCN) layers with BCN layers as well as with other layered structures such as MoS₂ and C₃N₄. While cross-linking BCN layers with other 2D sheets, we have exploited the existence of different surface functional groups on the graphene (COOH) and BN(NH₂) domains of the borocarbonitrides as quantitatively determined by FLOSS. Hence, we have thus obtained two different BCN–BCN assemblies differing in the location of the cross-linking and these are designated as GG/BCN–BCN and GBN/BCN–BCN, depending on which domains of the BCN are involved in cross-linking. In this study, we have determined the surface areas and CO₂ and H₂ adsorption properties of the cross-linked structures of two borocarbonitride compositions, (BN)_0.75C_0.25 and (BN)_0.3C_0.7. We have also studied their supercapacitor characteristics and photochemical catalytic activity for hydrogen generation. The study reveals that the covalently cross-linked BCN–BCN and BCN–MoS₂ assemblies exhibit increased surface areas and superior supercapacitor performance. The BCN composite with MoS₂ also shows high photochemical HER activity besides electrochemical HER activity comparable to Pt. This observation is significant since MoS₂ in the nanocomposite is in the 2H form. The present study demonstrates the novelty of this new class of materials generated by cross-linking of 2D sheets of inorganic graphene analogues and their potential applications.

Covalent cross-linking of 2D structures such as graphene, MoS₂ and C₃N₄ using coupling reactions affords the generation of novel materials with new or improved properties.

Preparation of MoS2-based polydopamine-modified core–shell nanocomposites with elevated adsorption performances

New molybdenum disulfide (MoS₂)-based core–shell nanocomposite materials were successfully prepared through the self-assembly of mussel-inspired chemistry. Characterization by Fourier transform infrared, thermogravimetric analysis, scanning electron microscope and transmission electron microscopy revealed that the surface of the flaked MoS₂ was homogeneously coated with a thin layer of polydopamine (PDA). Dye adsorption performances of the synthesized MoS₂–PDA nanocomposites were investigated at different pH values and reaction times. Compared with pure MoS₂ nanosheets, the obtained core–shell nanocomposites showed elevated adsorption performances and high stability, indicating their potential applications in wastewater treatment and composite materials.

New core–shell MoS₂–PDA nanocomposites are prepared via mussel-inspired chemistry and a simple interfacial self-assembly process, demonstrating potential applications in wastewater treatment and self-assembled core–shell composite materials.

Nanocomposites of C3N4 with Layers of MoS2 and Nitrogenated RGO, Obtained by Covalent Cross-Linking: Synthesis, Characterization, and HER Activity

Generation of hydrogen by photochemical, electrochemical, and other means is a vital area of research today, and a variety of materials have been explored as catalysts for this purpose. C₃N₄, MoS₂, and nitrogenated RGO (NRGO) are some of the important catalytic materials investigated for the hydrogen evolution reaction (HER) reaction, but the observed catalytic activities are somewhat marginal. Prompted by preliminary reports that covalent cross-linking of 2D materials to generate heteroassemblies or nanocomposites may have beneficial effect on the catalytic activity, we have synthesized nanocomposites wherein C₃N₄ is covalently bonded to MoS₂ or NRGO nanosheets. The photochemical HER activity of the C₃N₄-MoS₂ nanocomposite is found to be remarkable with an activity of 12778 μmol h^-1 g^-1 and a turnover frequency of 2.35 h^-1. The physical mixture of C₃N₄ and MoS₂, on the other hand, does not exhibit notable catalytic activity. Encouraged by this result, we have studied electrochemical HER activity of these composites as well. C₃N₄-MoS₂ shows superior activity relative to a physical mixture of MoS₂ and C₃N₄. Density functional theory calculations have been carried out to understand the HER activity of the nanocomposites. Charge-transfer between the components and greater planarity of cross-linked layers are important causes of the superior catalytic activity of the nanocomposites. Covalent linking of such 2D materials appears to be a worthwhile strategy for catalysis and other applications.

Covalent cross-linking as a strategy to generate novel materials based on layered (2D) and other low D structures

Covalent linking of 2D structures such as graphene, MoS₂and C₃N₄by employing coupling reactions provides a strategy to generate a variety of materials with new or improved properties.