Flower-like N-doped MoS2 for photocatalytic degradation of RhB by visible light irradiation

How can heteroatoms boost the performance of photoactive nanomaterials for wastewater purification?

Photocatalysis, as an alternative for treating persistent water pollutants, holds immense promise. However, limitations hinder sustained treatment and recycling under varying light conditions. This comprehensive review delves into the novel paradigm of metal and non-metal doping to overcome these challenges. It begins by discussing the fundamental principles of photocatalysis and its inherent limitations. Understanding these constraints is crucial for developing effective strategies. Band gap narrowing by metal and non-metal doping modifies the band gap, enabling visible-light absorption. Impurity energy levels and oxygen vacancies influenced the doping energy levels and surface defects. Interfacial electron transfer and charge carrier recombination are the most important factors that impact overall efficiency. The comparative analysis of nanomaterials are reviewed on various, including nanometal oxides, nanocarbon materials, and advanced two-dimensional structures. The synthesis process are narratively presented, emphasizing production yields, selectivity, and efficiency. The review has potential applications in the environment for efficient pollutant removal and water purification, economic cost-effective and scalable production and technological advancement catalyst design, in spite of its challenges in material stability, synthesis methods and optimizing band gaps. The novelty of the review paper is on the proposal of a new paradigm of heterojunctions of doped metal and non-metal photocatalysts to promise highly efficient water treatment. This review bridges the gap between fundamental research and practical applications, offering insights into tailored nano photocatalysts.

Efficient rhodamine B dye degradation by red mud-grapefruit peel biochar catalysts activated persulfate in water

The continuous and rapid development of textile industry intensifies rhodamine B dye (RhB) wastewater pollution. Meanwhile, massive red mud (RM) solid waste generated by the industrial alumina production process poses detrimental effects to the environment after leaching. For resource utilization and to reduce the expansion of RhB pollution, RM and peel red mud-biochar composite (RMBC) catalyst were synthesized in activating peroxydisulfate (PDS) for RhB degradation. Firstly, characterization results showed that compared to RM, RMBC had a higher content of catalytically active metals (Fe, Al, Ti) (higher than 0.92-4.18%), smaller pore size, and larger specific surface area (10 times), which verified RMBC had more potential catalytic oxidation activity. Secondly, under optimal dosage (catalyst, PDS), pH 4.6, and 20 mg L-1 RhB, it was found that the RhB degradation ratio of RM was 76.70%, which was reduced to 41% after three cycles, while that of RMBC was 89.98% and 67%, respectively. The results indicated that the performance of RMBC was significantly superior to that of RM. Furthermore, the quenching experiments, electron paramagnetic resonance spectroscopy tests, FTIR, and XPS analysis showed the function of O-H, C=O, C-O, Fe-O, and Fe-OH functional groups, which converted the PDS to the active state and hydrolyzed it to produce free radicals ([Formula: see text], 1O2, [Formula: see text]) for RhB degradation. And, Q Exactive Plus MS test obtained that RhB was degraded to CO2, H2O, and intermediate products. This study aimed to raise a new insight to the resource utilization of RM and the control of dye pollution.

Analysis of Photocatalytic Properties of NS-CQDs/g-C3N4 Composites

N- and S-doped CQDs were prepared using L-cysteine as a precursor. Different NS-CQDs/g-C3N4 composite photocatalysts were formed by modifying graphite-phase carbon nitride with different contents of NS-CQDs using a hydrothermal method. The morphology, constituent elements and functional groups of the composite photocatalysts were analyzed by SEM, EDS, TEM, Mapping, XRD and FT-IR as a proof of its successful preparation. Meanwhile, it was characterized by PL, UV-Vis DRS and electrochemical impedance, which proved that the CQDs could be used as an electronic memory in the composite system to accelerate the electron transfer induced by the photo-excitation of g-C3N4 and effectively inhibit the recombination of e--h+ improvement of the photocatalytic activity of g-C3N4. The stability of the composite photocatalysts under different conditions and the photodegradation activity of Rh B under visible light were investigated. It was found that the photocatalytic degradation efficiency of rhodamine B by NS-CQDS-modified g-C3N4 was significantly higher than that of pure g-C3N4, which could reach 90.82%, and its degradation rate was 3.5 times higher than that of pure g-C3N4. It was demonstrated by free radical trapping experiments that ·OH and ·O2- were the main active species in the photocatalytic degradation process, in which ·O2- played a guiding role.

Aerosol-Assisted Chemical Vapor Deposition of MoS2 with a Thiourea Sulfur Source: Single-Source Precursors vs Coreactant Mixtures

Aerosol-assisted chemical vapor deposition of MoS2 from solutions containing the single-source precursors cis-Mo(CO)4(TMTU)2 and Mo(CO)5(TMTU) in toluene was compared to depositions from the coreactant solution containing Mo(CO)6 and uncoordinated TMTU in toluene. The results were used to assess the significance of ligand precoordination on the properties of the deposited films. Raman spectra and GI-XRD patterns of the films show that the single-source precursors produced more intense and sharper signals for 2H-MoS2 as compared to the coreactant system of Mo(CO)6 and TMTU, which is indicative of improved crystallinity. SEM and XPS were also used to assess morphology and film composition. Thermolysis of cis-Mo(CO)4(TMTU)2 and analysis of the pyrolysis products by GC-MS and 1H NMR suggested a decomposition mechanism of the TMTU ligand where a terminal sulfido is generated on the molybdenum center with loss of a heteroatom stabilized carbene.

The association between oral and gut microbiota in male patients with alcohol dependence

Introduction

The relationship between oral and gut microbiota in alcohol dependence (AD) is not well understood, particularly the effects of oral microbiota on the intestinal microbiota. The current study aimed to explore the association between oral and gut microbiota in AD to clarify whether oral microbiota could ectopically colonize into the gut.

Methods

16S rRNA sequence libraries were used to compare oral and gut microbial profiles in persons with AD and healthy controls (HC). Source Tracker and NetShift were used to identify bacteria responsible for ectopic colonization and indicate the driver function of ectopic colonization bacteria.

Results

The α-diversity of oral microbiota and intestinal microbiota was significantly decreased in persons with AD (all p < 0.05). Principal coordinate analysis indicated greater similarity between oral and gut microbiota in persons with AD than that in HC, and oral-gut overlaps in microbiota were found for 9 genera in persons with AD relative to only 3 genera in HC. The contribution ratio of oral microbiota to intestinal microbiota composition in AD is 5.26% based on Source Tracker，and the AD with ectopic colonization showed the daily maximum standard drinks, red blood cell counts, hemoglobin content, and PACS scores decreasing (all p < 0.05).

Discussion

Results highlight the connection between oral-gut microbiota in AD and suggest novel potential mechanistic possibilities.

Cost-Effective and Highly Efficient Manganese-Doped MoS2 Nanosheets as Visible-Light-Driven Photocatalysts for Wastewater Treatment

One of the main objectives in wastewater treatment and sustainable energy production is to find photocatalysts that are favorably efficient and cost-effective. Transition-metal dichalcogenides (TMDs) are promising photocatalytic materials; out of all, MoS₂ is extensively studied as a cocatalyst in the TMD library due to its exceptional photocatalytic activity for the degradation of organic dyes due to its distinctive morphology, adequate optical absorption, and rich active sites. However, sulfur ions on the active edges facilitate the catalytic activity of MoS₂. On the basal planes, sulfur ions are catalytically inactive. Injecting metal atoms into the MoS₂ lattice is a handy approach for triggering the surface of the basal planes and enriching catalytically active sites. Effective band gap engineering, sulfur edges, and improved optical absorption of Mn-doped MoS₂ nanostructures are promising for improving their charge separation and photostimulated dye degradation activity. The percentage of dye degradation of MB under visible-light irradiations was found to be 89.87 and 100% for pristine and 20% Mn-doped MoS₂ in 150 and 90 min, respectively. However, the degradation of MB dye was increased when the doping concentration in MoS₂ increased from 5 to 20%. The kinetic study showed that the first-order kinetic model described the photodegradation mechanism well. After four cycles, the 20% Mn-doped MoS₂ catalysts maintained comparable catalytic efficacy, indicating its excellent stability. The results demonstrated that the Mn-doped MoS₂ nanostructures exhibit exceptional visible-light-driven photocatalytic activity and could perform well as a catalyst for industrial wastewater treatment.

2D Molybdenum Sulfide-Based Materials for Photo-Excited Antibacterial Application

Bacterial infections have seriously threatened human health and the abuse of natural or artificial antibiotics leads to bacterial resistance, so development of a new generation of antibacterial agents and treatment methods is urgent. 2D molybdenum sulfide (MoS₂ ) has good biocompatibility, high specific surface area to facilitate surface modification and drug loading, adjustable energy bandgap, and high near-infrared photothermal conversion efficiency (PCE), so it is often used for antibacterial application through its photothermal or photodynamic effects. This review comprehensively summarizes and discusses the fabrication processes, structural characteristics, antibacterial performance, and the corresponding mechanisms of MoS₂ -based materials as well as their representative antibacterial applications. In addition, the outlooks on the remaining challenges that should be addressed in the field of MoS₂ are also proposed.

High-Responsivity Gate-Tunable Ultraviolet-Visible Broadband Phototransistor Based on Graphene-WS2 Mixed-Dimensional (2D-0D) Heterostructure

Recent progress in the synthesis of highly stable, eco-friendly, cost-effective transition-metal dichalcogenide (TMDC) quantum dots (QDs) with their broadband absorption spectra and wavelength selectivity features have led to their increasing use in broadband photodetectors. With the solution-based processing, we demonstrate a superlarge (∼0.75 mm²), ultraviolet-visible (UV-vis) broadband (365-633 nm) phototransistor made of WS₂ QDs-decorated chemical vapor deposited (CVD) graphene as the active channel with extraordinary stability and durability under ambient conditions (without any degradation of photocurrent until 4 months after fabrication). Here, colloidal zero-dimensional (0D) WS₂ QDs are used as the photoabsorbing material, and graphene acts as the conducting channel. A high photoresponsivity (3.1 × 10² A/W), moderately high detectivity (∼8.9 × 10⁸ Jones), and low noise equivalent power (∼9.7 × 10^-11 W/Hz^0.5) are obtained at a low bias voltage (V_ds = 1 V) at an illumination of 365 nm with optical power as low as ∼0.8 μW/cm², which can be further tuned by modulating the gate bias. While comparing the photocurrent between two different morphologies of WS₂ [QDs and two-dimensional (2D) nanosheets], a significant enhancement of photocurrent is observed in the case of QD-based devices. Ab initio density functional theory (DFT)-based calculations further support our observation, revealing the role of quantum confinement in enhanced photoresponse. Our work reveals a strategy toward developing a scalable, cost-effective, high-performance hybrid mixed-dimensional (2D-0D) photodetector with graphene-WS₂ QDs for next-generation optoelectronic applications.

Advanced Strategies to Improve Performances of Molybdenum-Based Gas Sensors

Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications. Particularly, molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunable structural and physicochemical properties that meet sensor requirements. These materials have good durability, are naturally abundant, low cost, and have facile preparation, allowing scalable fabrication to fulfill the growing demand of susceptible sensor devices. Significant advances have been made in recent decades to design and fabricate various molybdenum oxides- and dichalcogenides-based sensing materials, though it is still challenging to achieve high performances. Therefore, many experimental and theoretical investigations have been devoted to exploring suitable approaches which can significantly enhance their gas sensing properties. This review comprehensively examines recent advanced strategies to improve the nanostructured molybdenum-based material performance for detecting harmful pollutants, dangerous gases, or even exhaled breath monitoring. The summary and future challenges to advance their gas sensing performances will also be presented.

Hydrothermal synthesis, characterization and photocatalytic activity of Mg doped MoS2

In this research work nanoparticles of Mg (0, 1, 2 and 3%) doped MoS2 are prepared by Hydrothermal method at 200 °C for 9 h. Scanning Electron Microscope (SEM) for surface morphology, Fourier Transform Infrared Spectroscopy (FTIR) for structural and chemical bonding and UV-visible spectroscopy for optical properties are used. SEM showed that sheet-like structure has changed into stone-like shaped when Mg has doped into MoS2. From FTIR, Mo–O, Mo=S, and H–O bond peaks are becoming dim and new chemical bonds S=O, Mo=O, Mg–O, CH and OH are forming with the increase of Mg doping. UV-visible spectroscopy showed that MoS2 has an indirect bandgap 2.21 eV. Band gap decreased from 1.84 to 1.82 eV when the Mg doping was increased from 1 to 2%, respectively. As Mg concentration was increased i.e. 3% then band gap increased to 1.88 eV. Photocatalytic activity (PCA) of undoped and Mg doped MoS2 is appraised by degrading rhodamine blue (RhB) and methylene blue (MB) dyes. The results showed that PCA (in presence of visible light) Mg doped MoS2 is greater than pure MoS2 which significantly increased the photocatalytic properties.

Hierarchical ultrathin layered MoS2@NiFe2O4 nanohybrids as a bifunctional catalyst for highly efficient oxygen evolution and organic pollutant degradation

Rational design and highly efficient dual-functional catalyst are still difficult to develop for electrocatalytic oxygen evolution reaction and degradation of RhB dye pollutant. Herein, we report a highly efficient "bandgap matching and interfacial coupling" strategy to synthesize nano-assembled ultrathin layered MoS₂@NiFe₂O₄ (MS@NiFeO) bifunctional catalyst constructed by the hydrothermal route and subsequently amine-hydrolysis. The OER performance of the prepared MS@NiFeO catalyst delivers a low overpotential of 290 mV at 10 mA/cm² and Tafel slope is 69.2 mV dec^-1 in an alkaline solution. In addition, the nano-assembled ultrathin layered structure of MS@NiFeO showed a highly efficient (96.37%) RhB dye degradation performance than that of MoS₂ nanosheets and NiFe₂O₄ nanostructures. Unique nanostructure of ultrathin layered MS@NiFeO with suitable band matching, interfacial charge transfer, high surface area and more active sites favored for the enhancement of the catalytic activity. This work presents an unpretentious construction and low-cost production strategy to synthesize bifunctional hybrid catalyst for oxygen evolution reaction as well as degradation of organic pollutant with superior efficiency and longer stability.

Interface enriched highly interlaced layered MoS2/NiS2 nanocomposites for the photocatalytic degradation of rhodamine B dye

In the past few decades, air and water pollution by organic dyes has become a serious concern due to their high toxicity. Removal of these organic dyes from polluted water bodies is a serious environmental concern and the development of new advanced photocatalytic materials for decomposing organic dyes can be a good solution. In this work, layered molybdenum disulfide/nickel disulfide (MoS2/NiS2) nanocomposites with various NiS2 content was synthesized by a one-step hydrothermal method using citric acid as a reducing agent. The X-ray diffraction pattern shows the hexagonal and cubical crystal structure of MoS2 and NiS2, respectively. Morphological analysis confirms the formation of MoS2/NiS2 nanosheets. The elemental composition of the samples was carried out by XPS, which shows a significant interaction between NiS2 and MoS2. The photocatalytic performance of MoS2/NiS2 nanocomposites was studied by the degradation of rhodamine B (RhB). Ni-4 sample shows higher photocatalytic activity with a maximum degradation of 90.61% under visible light irradiation for 32 min.

Engineering of Amorphous Structures and Sulfur Defects into Ultrathin FeS Nanosheets to Achieve Superior Electrocatalytic Alkaline Oxygen Evolution

Integration of amorphous structures and anion defects into ultrathin 2D materials has been identified as an effective strategy for boosting the electrocatalytic performance. However, the in-depth understanding of the relationship among the amorphous structure, vacancy defect, and catalytic activity is still obscure. Herein, a facile strategy was proposed to prepare ultrathin and amorphous Mo-FeS nanosheets (NSs) with abundant sulfur defects. Benefited from the ultrathin, amorphous nanostructure, and synergy effect of Mo-doping and sulfur defect, the Mo-FeS NSs manifested excellent electrocatalytic activity toward oxygen evolution reaction (OER) in alkaline medium, as shown by an ultralow overpotential of 210 mV at 10 mA cm^-2, a Tafel slope of 50 mV dec^-1, and retaining such good catalytic stability over 30 h. The efficient catalytic performance for Mo-FeS NSs is superior to the commercial IrO₂ and most reported top-performing electrocatalysts. Density functional theory calculations revealed that the accelerated electron/mass transfer over the oxygen-containing intermediates can be attributed to the amorphous structure and sulfur-rich defects caused by structural reconfiguration. Furthermore, the S vacancies could enhance the activity of its neighboring Fe-active sites, which was also beneficial to their OER kinetics. This work integrated both amorphous structures and sulfur vacancies into ultrathin 2D NSs and further systematically evaluated the OER performance, providing new insights for the design of amorphous-layered electrocatalysts.

A two-step gas/liquid strategy for the production of N-doped defect-rich transition metal dichalcogenide nanosheets and their antibacterial applications

Herein, we developed a general two-step gas expansion and exfoliation strategy based on a urea-assisted hydrothermal process combined with sonication exfoliation for the production of nitrogen (N)-doped plus defect-rich transition metal dichalcogenide (TMD) nanosheets (NSs) such as N-MoS₂ and N-WS₂ NSs. The interlayers of bulk MoS₂ (or WS₂) were expanded with urea molecules dissolved in distilled water, which were decomposed to NH₃ during the hydrothermal process. Simultaneously, sulfur atoms were partly replaced by N atoms to achieve N doping. Subsequently, sonication exfoliation of the urea-treated bulk MoS₂ (or WS₂) promoted the production of defect-rich NSs. Importantly, the defect-rich N-MoS₂ and N-WS₂ NSs exhibit enhanced peroxidase-like catalytic activity after being captured by bacteria, and can catalyze hydrogen peroxide (H₂O₂) to produce more toxic hydroxyl radicals (˙OH) than non-N-doped MoS₂ or WS₂ NSs. As a result, the N-MoS₂ or N-WS₂ NSs were capable of effectively killing Gram-negative ampicillin resistant Escherichia coli (Amp^rE. coli) and Gram-positive endospore-forming Bacillus subtilis (B. subtilis) and promoting bacteria-infected wound healing. This work not only provides a simple, universal exfoliation strategy for producing defect-rich N-doped TMD NSs but also provides a promising catalytic antibacterial option and has potential for many other catalytic applications.

A computational evaluation of MoS2-based materials for the electrocatalytic oxygen reduction reaction

The potential of modified MoS₂-based materials in oxygen reduction reaction (ORR) was evaluated by DFT calculations.

Nickel oxide decorated MoS2nanosheet-based non-enzymatic sensor for the selective detection of glucose

Understanding blood glucose levels in our body can be a key part in identifying and diagnosing prediabetes. Herein, nickel oxide (NiO) decorated molybdenum disulfide (MoS₂) nanosheets have been synthesized via a hydrothermal process to develop a non-enzymatic sensor for the detection of glucose. The surface morphology of the NiO/MoS₂ nanocomposite was comprehensively investigated by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analysis. The electro-catalytic activity of the as-prepared NiO/MoS₂ nanocomposite towards glucose oxidation was investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and amperometry in 0.1 M NaOH. The NiO/MoS₂ nanocomposite-based sensor showed outstanding electrocatalytic activity for the direct electro-oxidation of glucose due to it having more catalytic active sites, good conductivity, excellent electron transport and high specific surface area. Meanwhile, the NiO/MoS₂ modified glassy carbon electrode (GCE) showed a linear range of glucose detection from 0.01 to 10 mM by amperometry at 0.55 V. The effect of other common interferent molecules on the electrode response was also tested using alanine, l-cysteine, fructose, hydrogen peroxide, lactose, uric acid, dopamine and ascorbic acid. These molecules did not interfere in the detection of glucose. Moreover, this NiO/MoS₂/GCE sensor offered rapid response (2 s) and a wide linear range with a detection limit of 1.62 μM for glucose. The reproducibility, repeatability and stability of the sensor were also evaluated. The real application of the sensor was tested in a blood serum sample in the absence and presence of spiked glucose and its recovery values (96.1 to 99.8%) indicated that this method can be successfully applied to detect glucose in real samples.

This study reported that NiO/MoS₂ based nanocomposite can be used as an electrocatalytic material to detect glucose with high selectivity in a blood serum.

Photogalvanic Effect in Nitrogen-Doped Monolayer MoS2 from First Principles

We investigate the photogalvanic effect in nitrogen-doped monolayer molybdenum disulfide (MoS₂) under the perpendicular irradiation, using first-principles calculations combined with non-equilibrium Green function formalism. We provide a detailed analysis on the behavior of photoresponse based on the band structure and in particular the joint density of states. We thereby identify different mechanisms leading to the existence of zero points, where the photocurrent vanishes. In particular, while the zero point in the linear photovoltaic effect is due to forbidden transition, their appearance in the circular photovoltaic effect results from the identical intensity splitting of the valance band and the conduction band in the presence of Rashba and Dresslhaus spin-orbit coupling. Furthermore, our results reveal a strong circular photogalvanic effect of nitrogen-doped monolayer MoS₂, which is two orders of magnitude larger than that induced by the linearly polarized light.

3D Carbon Foam Supported Edge-Rich N-Doped MoS2 Nanoflakes for Enhanced Electrocatalytic Hydrogen Evolution

Molybdenum disulfide (MoS₂ ) is one of the most promising alternatives to the Pt-based electrocatalysts for the hydrogen evolution reaction (HER). However, its performance is currently limited by insufficient active edge sites and poor electron transport. Hence, enormous efforts have been devoted to constructing more active edge sites and improving conductivity to obtain enhanced electrocatalytic performance. Herein, the 3D carbon foam (denoted as CF) supported edge-rich N-doped MoS₂ nanoflakes were successfully fabricated by using the commercially available polyurethane foam (PU) as the 3D substrate and PMo₁₂ O₄₀ ^3- clusters (denoted as PMo₁₂ ) as the Mo source through redox polymerization, followed by sulfurization. Owing to the uniform distribution of nanoscale Mo sources and 3D carbon foam substrate, the as-prepared MoS₂ -CF composite possessed well-exposed active edge sites and enhanced electrical conductivity. Systematic investigation demonstrated that the MoS₂ -CF composite showed high HER performance with a low overpotential of 92 mV in 1.0 m KOH and 155 mV in 0.5 m H₂ SO₄ at a current density of 10 mA cm^-2 . This work offers a new pathway for the rational design of MoS₂ -based HER electrocatalysts.

Recent Progress on Irradiation-Induced Defect Engineering of Two-Dimensional 2H-MoS2 Few Layers

Atom-thick two-dimensional materials usually possess unique properties compared to their bulk counterparts. Their properties are significantly affected by defects, which could be uncontrollably introduced by irradiation. The effects of electromagnetic irradiation and particle irradiation on 2H MoS 2 two-dimensional nanolayers are reviewed in this paper, covering heavy ions, protons, electrons, gamma rays, X-rays, ultraviolet light, terahertz, and infrared irradiation. Various defects in MoS 2 layers were created by the defect engineering. Here we focus on their influence on the structural, electronic, catalytic, and magnetic performance of the 2D materials. Additionally, irradiation-induced doping is discussed and involved.

Phase Modulation of (1T-2H)-MoSe2/TiC-C Shell/Core Arrays via Nitrogen Doping for Highly Efficient Hydrogen Evolution Reaction

Tailoring molybdenum selenide electrocatalysts with tunable phase and morphology is of great importance for advancement of hydrogen evolution reaction (HER). In this work, phase- and morphology-modulated N-doped MoSe2 /TiC-C shell/core arrays through a facile hydrothermal and postannealing treatment strategy are reported. Highly conductive TiC-C nanorod arrays serve as the backbone for MoSe2 nanosheets to form high-quality MoSe2 /TiC-C shell/core arrays. Impressively, continuous phase modulation of MoSe2 is realized on the MoSe2 /TiC-C arrays. Except for the pure 1T-MoSe2 and 2H-MoSe2 , mixed (1T-2H)-MoSe2 nanosheets are achieved in the N-MoSe2 by N doping and demonstrated by spherical aberration electron microscope. Plausible mechanism of phase transformation and different doping sites of N atom are proposed via theoretical calculation. The much smaller energy barrier, longer HSe bond length, and diminished bandgap endow N-MoSe2 /TiC-C arrays with substantially superior HER performance compared to 1T and 2H phase counterparts. Impressively, the designed N-MoSe2 /TiC-C arrays exhibit a low overpotential of 137 mV at a large current density of 100 mA cm-2 , and a small Tafel slope of 32 mV dec-1 . Our results pave the way to unravel the enhancement mechanism of HER on 2D transition metal dichalcogenides by N doping.

Facile and Cost-Efficient Synthesis of Quasi-0D/2D ZnO/MoS2 Nanocomposites for Highly Enhanced Visible-Light-Driven Photocatalytic Degradation of Organic Pollutants and Antibiotics

Nanoscale transition-metal dichalcogenide materials showed promising potential for visible-light responsive photocatalysis. Here, we report our investigations on the synthesis of heterodimensional nanostructures of two-dimensional (2D) ultrathin MoS₂ nanosheets interspersed with ZnO nanoparticles by using a facile two-step method consisting of sonication-aided exfoliation technique followed by a wet chemical process. The photocatalytic activity of the nanocomposites was examined by studying the degradation of different organic dye pollutants and tetracycline, a common antibiotic, under visible-light irradiation. It is found that within 30 min more than 90 % of the model organic dye was photodegraded by the optimized quasi-0D/2D hybrid nanomaterial. The reaction rate of pollutant degradation is about five and eight times higher than those of the pristine MoS₂ naonosheets and P25 photocatalysts, respectively. The outstanding photocatalytic activity of the heterodimensional hybrids can be attributed to a few beneficial features from the synergetic effects. Most importantly, the intimate junction between ZnO and MoS₂ facilitates the separation of photogenerated carriers, leading to the enhancement of photocatalytic efficiency. A tentative photocatalytic degradation mechanism was proposed and tested. Overall, the present work provides valuable insights for the exploration of cost-effective nanoscale heterodimensional hybrids constructed from atomically thin layered materials.

Green synthesis of MoS2 nanoflowers for efficient degradation of methylene blue and crystal violet dyes under natural sun light conditions

Hydrothermally synthesized MoS₂ NFs have been employed as an efficient photocatalyst for the degradation of MB and CV dyes under sunlight.

Two-Dimensional Transition Metal Oxide and Chalcogenide-Based Photocatalysts

Two-dimensional (2D) transition metal oxide and chalcogenide (TMO&C)-based photocatalysts have recently attracted significant attention for addressing the current worldwide challenges of energy shortage and environmental pollution. The ultrahigh surface area and unconventional physiochemical, electronic and optical properties of 2D TMO&Cs have been demonstrated to facilitate photocatalytic applications. This review provides a concise overview of properties, synthesis methods and applications of 2D TMO&C-based photocatalysts. Particular attention is paid on the emerging strategies to improve the abilities of light harvesting and photoinduced charge separation for enhancing photocatalytic performances, which include elemental doping, surface functionalization as well as heterojunctions with semiconducting and conductive materials. The future opportunities regarding the research pathways of 2D TMO&C-based photocatalysts are also presented.

First-principles study of nonmetal doped monolayer MoSe2 for tunable electronic and photocatalytic properties

Recently, two dimensional transition metal dichalcogenides become popular research topics because of their unique crystal and electronic structure. In this work, the geometrical structure, electronic, electrical transport, redox potentials and photocatalytic properties of nonmetal (H, B, C, Si, N, P, As, O, S, Te, F, Cl, Br and I) doped monolayer MoSe₂ were investigated by first principle calculations. The binding energy indicates that nonmetal doped MoSe₂ are energetically favorable compared to Se vacancies, except B- and C-doped. We have found that nonmetal dopants with an even number of valence electrons doped MoSe₂ have p-type conductivity. On the contrary, nonmetal dopants with an odd number of valence electrons doped MoSe₂ have p-type or n-type conductivity; and they have better photocatalytic performance.

Directional Construction of Vertical Nitrogen-Doped 1T-2H MoSe2 /Graphene Shell/Core Nanoflake Arrays for Efficient Hydrogen Evolution Reaction

The low utilization of active sites and sluggish reaction kinetics of MoSe₂ severely impede its commercial application as electrocatalyst for hydrogen evolution reaction (HER). To address these two issues, the first example of introducing 1T MoSe₂ and N dopant into vertical 2H MoSe₂ /graphene shell/core nanoflake arrays that remarkably boost their HER activity is herein described. By means of the improved conductivity, rich catalytic active sites and highly accessible surface area as a result of the introduction of 1T MoSe₂ and N doping as well as the unique structural features, the N-doped 1T-2H MoSe₂ /graphene (N-MoSe₂ /VG) shell/core nanoflake arrays show substantially enhanced HER activity. Remarkably, the N-MoSe₂ /VG nanoflakes exhibit a relatively low onset potential of 45 mV and overpotential of 98 mV (vs RHE) at 10 mA cm^-2 with excellent long-term stability (no decay after 20 000 cycles), outperforming most of the recently reported Mo-based electrocatalysts. The success of improving the electrochemical performance via the introduction of 1T phase and N dopant offers new opportunities in the development of high-performance MoSe₂ -based electrodes for other energy-related applications.

Simple and Large Scale Construction of MoS2-g-C3N4 Heterostructures Using Mechanochemistry for High Performance Electrochemical Supercapacitor and Visible Light Photocatalytic Applications

The design of heterojunctions for efficient electrochemical energy storage and environmental remediation are promising for future energy and environment applications. In this study, a molybdenum disulfide-graphitic carbon nitride (MoS₂-g-C₃N₄) heterojunction was designed by applying simple mechanochemistry, which can be scaled up for mass production. The physical-chemical and photophysical properties of the as-prepared MoS₂-g-C₃N₄ heterojunction were analyzed using a range of characterization techniques. The supercapacitance performance was determined by electrochemical half-cell measurements, and visible light-induced photoelectrochemical and photocatalytic performance was studied using photocurrent and model organic pollutant degradation experiments. The resulting MoS₂-g-C₃N₄ under the optimized experimental conditions showed significantly higher photocatalytic activity and photoelectrochemical performance under similar visible photoirradiation conditions compared to the bare materials. The resulting heterostructure electrode delivered a higher capacitance of 240.85 F/g than the bare material (48.77 F/g) with good capacitance retention. The superior performance was attributed mainly to the robust light harvesting ability, improved charge separation, high surface area, increased mass transfer, and capacitive and conductive behavior. The convenient and mass production of heterojunctions using a simple and cost-effective method will provide a good example for the efficient design of visible light active photocatalysts and capacitor electrode materials for environmental remediation and energy storage device applications.

Highly efficient visible-light photocatalytic activity of MoS2–TiO2 mixtures hybrid photocatalyst and functional properties

2D-layered molybdenum disulfide (MoS₂) and MoS₂/TiO₂ nanocomposite were synthesized by a hydrothermal method.

Enhanced lubrication and photocatalytic degradation of liquid paraffin by coral-like MoS2

Coral-like MoS₂ obtained by hydrothermal method can serve as both lubricating additive and photo-catalyst at different working stages in the full life cycle of LP, which exhibits great potential in developing environment-friendly lubricating systems.