Hydrothermal green synthesis of MoS2 nanosheets for pollution abatement and antifungal applications

In this study, we report a green synthesis of MoS₂ nanosheets (NSs) using a facile hydrothermal technique in the presence of l-cysteine. l-Cysteine can serve as a greener source of sulfur as well as a capping agent to help the growth of MoS₂ nanosheets. The prepared materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), electron transmission microscopy (TEM), X-ray photoelectron microscopy (XPS), and Brunauer, Emmett, and Teller (BET) analysis. The results showed that MoS₂ NSs are of high crystallinity with a lattice spacing of 0.61 nm. The optical bandgap of MoS₂ NSs nanosheets prepared using l-cysteine as a source of sulfur was found to be 1.79 eV. The photocatalytic degradation of MoS₂ NSs towards methylene orange (MO) and rhodamine blue (RB) dyes under sunlight was found to be promising for practical applications. The fast kinetics of degradation of MO and RhB was observed over a wide range of pH range. Moreover, MoS₂ NSs showed excellent antifungal activities against Trichophyton mentagrophytes and Penicillium chrysogenum fungus.

In this study, we report a green synthesis of MoS₂ nanosheets (NSs) using a facile hydrothermal technique in the presence of l-cysteine.     

The synthesis of two-dimensional MoS2 nanosheets with enhanced tribological properties as oil additives

The use of MoS₂ nanosheets as oil additives has been proved effective to reduce friction and wear. Furthermore, it has been suggested that the synthesis of MoS₂ nanosheets with an ultrathin structure could benefit the friction and wear reduction, as they would penetrate into the contact area easily. In this paper, two-dimensional MoS₂ nanosheets were successfully fabricated by a solvothermal method with the aid of oleylamine. Meanwhile, the synthesized MoS₂ nanosheets exhibited perfect dispersing stability in paraffin oil, due to the surface modification by oleylamine molecules. The friction and wear properties of the synthesized MoS₂ nanosheets as oil additives were investigated using a ball-on-disk tribotester. The results showed that the two-dimensional MoS₂ nanosheets exhibited enhanced friction-reducing and antiwear behaviors as compared to the multilayered MoS₂ nanosheets. The prominent tribological performance of the two-dimensional MoS₂ nanosheets was attributed to the formation of a thick tribofilm inside the wear tracks, which was confirmed by XPS analyses of the rubbing interfaces.

Two-dimensional MoS₂ nansheets (2D MoS₂) with enhanced tribological properties were successfully fabricated with the aid of oleylamine.     

Morphology-controlled synthesis of MoS2 using citric acid as a complexing agent and self-assembly inducer for high electrochemical performance

Two-dimensional MoS₂ with a controllable morphology was prepared via a simple one-step hydrothermal method. Citric acid was used as a complexing agent and self-assembly inducer. The morphology of MoS₂ changed from clusters to nanosheets, and, eventually, to stacked nanorods. A formation mechanism is proposed for the observed evolution of the morphology. The nanosheet structure presents a relatively large specific surface area, more exposed active sites and greater 1T phase content compared to the other morphologies. The electrochemical performance tests show that the MoS₂ nanosheets exhibit excellent electrochemical behavior. Their specific capacitance is 320.5 F g⁻¹, and their capacitance retention is up to 95% after 5000 cycles at 5 mA cm⁻². This work provides a feasible approach for changing the morphology of MoS₂ for high efficiency electrode materials for supercapacitors.

Two-dimensional MoS₂ with a controllable morphology was prepared via a simple one-step hydrothermal method.     

Preparation of a MoS2/carbon nanotube composite as an electrode material for high-performance supercapacitors

MoS₂ and MoS₂/carbon allotrope (MoS₂/C) composites for use as anodes in supercapacitors were prepared via a facile hydrothermal method. In this study, we report the effects of various carbon-based materials (2D graphene nanosheet (GNS), 1D carbon nanotube (CNT), and 0D nano carbon (NC)) on the electrochemical performances. Among all nanocomposites studied, MoS₂/CNT exhibited the best electrochemical performance. Specifically, the MoS₂/CNT composite exhibits remarkable performances with a high specific capacitance of 402 F g⁻¹ at a current density of 1 A g⁻¹ and an outstanding cycling stability with 81.9% capacitance retention after 10 000 continuous charge–discharge cycles at a high current density of 1 A g⁻¹, making it adaptive for high-performance supercapacitors. The superiority of MoS₂/CNT was investigated by field emission scanning electron microscopy and transmission electron microscopy, which showed that MoS₂ nanosheets were uniformly loaded into the three-dimensional interconnected network of nanotubes, providing an excellent three dimensional charge transfer network and electrolyte diffusion channels while effectively buffering the collapse and aggregation of active materials during charge–discharge processes. Overall, the MoS₂/CNT nanocomposite synthesized by a simple hydrothermal process presents a new and promising candidate for high-performance anodes for supercapacitors.

The effect of carbon supports on the electrochemical performance of MoS₂ nanosheets for supercapacitor applications was investigated.     

Shape controllable MoS2 nanocrystals prepared by the single precursor route for electrocatalytic hydrogen evolution

MoS₂ has attracted great attention as a prospective electrocatalyst for generating hydrogen via water electrolysis due to its abundant and inexpensive sources. However, bulk MoS₂ has weak electrocatalytic activity because of its low electrical conductivity and few edge-active sites. Controllable synthesis of MoS₂ with ultrasmall size or complex morphology may be an available strategy to boost its conductivity and edge-active sites. Herein, a facile single-precursor strategy was developed to prepare nanoscale MoS₂ with various morphologies, including quantum dots, nanorods, nanoribbons, and nanosheets. In-depth studies show that the formation of MoS₂ with various shapes is determined by both kinetic and thermodynamic factors such as reaction time and temperature. Electrocatalytic tests reveal that MoS₂ quantum dots have high electrocatalytic performance with a low overpotential of 255 mV and a small Tafel slope of 66 mV dec⁻¹ due to the abundant exposed active edges and excellent intrinsic conductivity.

A facile single-precursor route was designed for the synthesis of shape- and size-controllable MoS₂ nanocrystals, including MoS₂ QDs, nanorods, nanoribbons, and nanosheets. Among them, MoS₂ QDs exhibit higher electrocatalytic activity in HRE.     

Controllable growth of MoS2 nanosheets on TiO2 burst nanotubes and their photocatalytic activity

MoS₂ nanosheets were grown on TiO₂ nanotubes by the simple hydrothermal method for the first time. The layer-by-layer growth of MoS₂ nanosheets led to a significant increase in the specific surface area of TiO₂/MoS₂ burst tube composites compared with TiO₂ burst tubes, a significantly enhanced ability to separate photo-induced carriers, and synergistic adsorption and visible light catalytic activity of dye molecules. The maximum adsorption (q_max) of MB was 72.46 mg g⁻¹. In addition, 94.1% of MB could be degraded after 30 minutes of visible light irradiation. The microsurface morphology, structure, chemical composition, element valence and band width of TiO₂/MoS₂ nanocomposites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The mechanism of photocatalytic reaction was studied via free radical capture experiments.

MoS₂ nanosheets were grown on TiO₂ nanotubes by the simple hydrothermal method for the first time.     

Ultrathin 2D metal–organic framework nanosheets prepared via sonication exfoliation of membranes from interfacial growth and exhibition of enhanced catalytic activity by their gold nanocomposites

Ultrathin two-dimensional (2D) metal–organic framework (MOF) nanosheets were prepared by a facile sonication exfoliation of MOF membranes from interfacial growth. The stacked form of nanosheets constituting the MOF membranes was significantly different to that of its layered MOF counterparts. This led to decreased interaction between nanosheets, so they could exfoliate readily from the MOF membranes. Moreover, Au nanoparticles were introduced to form nanocomposites. Enhanced catalytic activity and long-term stability of these nanocomposites were observed by a model reaction of the reduction of 4-nitrophenol to 4-aminophenol. This preparation method could be extended to other 2D MOF nanosheets and their nanocomposites.

Cu-MOF nanosheets were prepared by sonication exfoliation and the Au/Cu-MOF nanocomposites exhibited higher catalytic activity than pure Au NPs.     

Relationship between the structure and catalytic performance of MoS2 with different surfactant-assisted syntheses in the hydrodesulfurization reaction of 4,6-DMDBT

Surfactants are important factors in the hydrothermal synthesis of MoS₂ with different morphologies. Herein, we report the synthesis of MoS₂via the hydrothermal method combined with a single-source precursor with the assistance of different surfactants (CTAB/SDS/SDBS). The synthesis mechanisms of MoS₂ with different morphologies and their effects on 4,6-DMDBT in hydrodesulfurization (HDS) have been systematically studied. MoS₂-CTAB was prepared by the adsorption of molybdate radicals, nucleation and formation. MoS₂-SDS and MoS₂-SDBS were synthesized via four steps, namely, adsorption, insertion, exfoliation and assembly, and the relationship between the morphology-structure-performance of MoS₂ in the hydrodesulfurization of 4,6-DMDBT was investigated. It was established that the desulfurization rate of MoS₂, HYD ratio and selectivity of the MoS₂ increased in the order: MoS₂-SDBS > MoS₂-CTAB > MoS₂-SDS, which exhibited a positive correlation with the average number of layers and dispersion, and a negative correlation with the average slab length and the ratio of the Mo edge/corner sites of MoS₂. Among all the MoS₂, MoS₂-SDBS exhibited the best HDS performance.

Surfactants are important factors in the hydrothermal synthesis of MoS₂ with different morphologies.     

Mixed-solvent liquid exfoliated MoS2 NPs as peroxidase mimetics for colorimetric detection of H2O2 and glucose

Ultra-small molybdenum disulfide nanoparticles (MoS₂ NPs) were prepared by a facile liquid exfoliation method with ethanol/water as the solvent. The produced MoS₂ NPs were of high purity due to the easily removable ethanol/water solution. The prepared MoS₂ NPs exhibited an intrinsic peroxidase-like activity in analogy to that of horseradish peroxidase (HRP). A custom-made spectrometer was employed to investigate the peroxidase-like activity of MoS₂ NPs in the presence of H₂O₂ and glucose. The change in absorption detected from MoS₂ NPs is proportional to the amount of target. The calibration curve of H₂O₂ and glucose shows a good relationship between the concentration of target and the change in the absorption of MoS₂ NPs. The limit of detection of H₂O₂ and glucose achieved by this method could approach 1.25 μM and 7 μM respectively. This method has been applied for the detection of glucose in serum from humans. Therefore, these produced MoS₂ NPs offer an alternative high-efficiency and economic way to detect diabetes.

Ultra-small molybdenum disulfide nanoparticles (MoS₂ NPs) prepared by a facile liquid exfoliation method is capable of detecting the presence of H₂O₂ and glucose. This novel colorimetric method offers an alternative way to detect diabetes.     

Facile synthesis of highly conductive MoS2/graphene nanohybrids with hetero-structures as excellent microwave absorbers

Two-dimensional (2D) MoS₂/graphene nanosheet (MoS₂/GN) hybrids have been demonstrated to be promising microwave absorption (MA) materials due to their unique chemical and physical properties as well as rich impedance matching. However, the reported strategies for preparing MoS₂/GN hybrids have limited their application potential due to the complex, high-cost and inefficient preparation processes. On the other hand, it is of note that the main source of graphene is based on converting insulating graphene oxides (GO) back to conductive reduced graphene oxides (RGO). Thus, the MA performance of obtained MoS₂/RGO nanohybrids is greatly affected by the conversion process of GO. In this work, we prepared the MoS₂/GN hybrids by a facile hydrothermal method with directly introducing highly pure and electroconductive GNs. It is found that the highest reflection loss value of the sample-wax containing 40% MoS₂/GN is −57.31 dB at a thickness of 2.58 mm, and the bandwidth of RL values less than −10 dB can reach up to 12.28 GHz (from 5.72 to 18 GHz) when an appropriate absorber thickness between 1.5 and 4 mm is chosen. The excellent MA performances emanate from effective conjugation of MoS₂ with GN (Mo–C bond between the interfaces), which provides the dielectric loss caused by multi-relaxation, conductance, and polarization. Taking into account the facile synthesis route and their excellent MA performance, the MoS₂/GNs hybrid nanosheets and those composite materials with similar isomorphic hetero-structures are very promising for a wide range of MA applications.

Two-dimensional (2D) MoS₂/graphene nanosheet (MoS₂/GN) hybrids have been demonstrated to be promising microwave absorption (MA) materials due to their unique chemical and physical properties as well as rich impedance matching.     

Synergistic lubrication of a porous MoS2-POSS nanohybrid

A porous MoS₂-polyhedral oligomeric silsesquioxane (POSS) nanohybrid was prepared from octavinyl-POSS nanoparticles and MoS₂ nanosheets for the first time, the structure and composition of which were confirmed by X-ray powder diffraction (XRD), Fourier-transform infrared spectra (FTIR), scanning electron microscopy (SEM), energy dispersive spectra (EDS) and thermal gravimetric analysis (TGA). As a comparison, MoS₂ nanosheets, octavinyl-POSS and MoS₂-POSS nanohybrid were used as lubricating additives for liquid paraffin (LP), which decreased the friction coefficients of LP by 7.8% (MoS₂), 14.1% (octavinyl-POSS), and 18.8% (MoS₂-POSS). Compared with MoS₂ and octavinyl-POSS, the MoS₂-POSS nanohybrid can be dispersed in organic solvents more homogeneously without adscititious dispersants or surfactants due to its better organic compatibilities. SEM and EDS analyses indicate that a synergistic frictional effect is responsible for the improved friction-reduction and anti-wear behavior.

A porous MoS₂-POSS nanohybrid is used as a lubricating additive, and synergistic lubrication is propitious for reducing the friction coefficient.     

Toward heterostructured transition metal hybrids with highly promoted electrochemical hydrogen evolution

It is essential to precisely develop low-cost and sustainable electrocatalysts for the hydrogen evolution reaction. Herein, we explore a robust and controllable hydrothermal approach to synthesize defect-rich MoS₂ nanoflakes on exfoliated MoS₂ and WS₂. Such well-designed hetero-structural hybrids of MoS₂/exfoliated MoS₂ and MoS₂/exfoliated WS₂ exhibit dramatically promoted electrochemical activity and high stability. The as-grown MoS₂ nanoflakes hybridized on exfoliated MoS₂ and WS₂ generate abundant active edge sites (rich in basal defects) and unsaturated sulfur atoms, resulting in highly enhanced electrocatalytic performance. This is expected to pave the way towards a significant improvement in transition metal dichalcogenide heterostructures as electrocatalysts.

Low-cost and sustainable transition metal dichalcogenide heterostructures are developed via a hydrothermal approach, which could greatly promote their electrochemical properties for HER performance as electrocatalysts.     

An integrated electrode based on nanoflakes of MoS2 on carbon cloth for enhanced lithium storage

Due to its high specific capacity (in theory), molybdenum disulfide (MoS₂) has been recognized as a plausible substitute in lithium-ion batteries (LIBs). However, it suffers from an inferior electric conductivity and a substantial volume change during Li⁺ insertion/extraction. By using a facile hydrothermal method, a flexible free-standing MoS₂ electrode has here been fabricated onto a carbon cloth substrate. The grafting of ultrathin MoS₂ nanoflakes onto the carbon cloth framework (forming CC@MoS₂), was shown to facilitate an improved electron transport, as well as an enhanced Li⁺ transport. As expected, the as-obtained CC@MoS₂ electrode was observed to exhibit an excellent lithium storage performance. It delivers a high discharge specific capacity of 2.42 mA h cm⁻² at 0.7 mA cm⁻² (even after 100 cycles), which is an impressive result.

Integrated carbon cloth@MoS₂ electrode is fabricated via a facile hydrothermal method as a binder-free anode for lithium-ion batteries.     

A reclaimed piezoelectric catalyst of MoS2@TNr composites as high-performance anode materials for supercapacitors

A piezoelectric catalyst of the MoS₂@TNr composite (MoS₂ nanosheets composited with TiO₂ nanorods) was synthesized by a two-step hydrothermal method, and can be recycled and reused as an advanced anode material for supercapacitors. In the dark, the MoS₂@TNr composite exhibited ultra-fast piezoelectric catalytic performance and good cycle stability on dye degradation; within 10 min, nearly all rhodamine B (50 mL, 20 ppm) was removed from the solution with the assistance of magnetic stirring. After the 5 cycle degradation reaction, the catalyst was reclaimed and applied to electrochemical testing, which showed better supercapacitor capacitance properties than the fresh catalyst due to the introduction of oxygen vacancies generated from the piezoelectric degradation process. The reclaimed catalyst demonstrated an excellent specific capacitance of 249 F g⁻¹ at 1 A g⁻¹, and 92% capacitance retention after 10 000 cycles. Furthermore, as the current density increased to 30 A g⁻¹, the capacitance could maintain 58% of the initial value. Thus, it can be concluded that the abandoned catalysts may serve as a potential electrode material for energy storage; simultaneously, the reutilization could eliminate secondary pollution and decrease the energy consumption in efficiency.

A piezoelectric catalyst of the MoS₂@TNr composite (MoS₂ nanosheets composited with TiO₂ nanorods) was synthesized by a two-step hydrothermal method, and can be recycled and reused as an advanced anode material for supercapacitors.     

Construction of a Au@MoS2 composite nanosheet biosensor for the ultrasensitive detection of a neurotransmitter and understanding of its mechanism based on DFT calculations

MoS₂ nanosheets can be applied as electrochemical biosensors to selectively and sensitively respond to the surrounding environment and detect various biomolecules due to their large specific surface area and unique physicochemical properties. In this paper, single-layer or few-layer MoS₂ nanosheets were prepared by an improved liquid phase stripping method, and then combining the unique material characteristics of MoS₂ and the metallic property of Au nanoparticles (AuNPs), Au@MoS₂ composite nanosheets were synthesized based on MoS₂ nanosheets. Then, the structure and properties of MoS₂ nanosheets and Au@MoS₂ composite nanosheets were comprehensively characterized. The results proved that AuNPs were successfully loaded on MoS₂ nanosheets. At the same time, on the basis of the successful preparation of Au@MoS₂ composite nanosheets, an electrochemical biosensor targeting dopamine was successfully constructed by cyclic voltammetry. The linear detection range was 0.5–350 μM, and the detection limit was 0.2 μM. The high-sensitive electrochemical detection of dopamine has been achieved, which provides a new idea for the application of MoS₂-based nanomaterials in the biosensing of neurotransmitters. In addition, density functional theory (DFT) was used to explore the electrochemical performance of Au@MoS₂ composite nanosheets. The results show that the adsorption of Au atoms on the MoS₂ 2D structure improves the conductivity of MoS₂ nanosheets, which theoretically supports the possibilities of its application as a platform for the ultrasensitive detection of neurotransmitters or other biomolecules in the field of disease diagnosis.

An electrochemical biosensor based on Au@MoS₂ composite nanosheets was successfully prepared for the high-sensitivity detection of dopamine.     

Facile synthesis of aqueous-dispersed luminescent nanosheets from non-layered lanthanum hexaboride

Two-dimensional nanosheets of non-layered materials have been considered as inaccessible through exfoliation techniques, due to their intrinsic three-dimensional lattice structure. Herein we report the successful synthesis of nanosheets from non-layered, lanthanum hexaboride through a facile, solution-assisted, surfactant-free, sonication. The morphological studies clearly show the presence of nanosheets having thickness of a few nanometers, and having lateral dimensions of several hundreds of nanometres. The as-fabricated nanosheets were found to be rich in hydroxyl groups, and hence exhibit excellent dispersion stability in water. The aqueous-dispersed nanosheets demonstrate excitation-wavelength dependent luminescence in the blue-cyan region, when excited with UV-light.

Nanosheets were synthesised by incorporating probe sonication and grinding of an aqueous dispersion of non-layered lanthanam hexaboride.     

Enhanced hydrogen evolution reaction activity of hydrogen-annealed vertical MoS2 nanosheets

Molybdenum disulfide (MoS₂) is a promising electrocatalyst for hydrogen evolution reaction (HER), but only edges and S-vacancies are catalytic active sites for the HER. Therefore, it is crucial to increase edge sites and S-vacancies for enhancing the HER activity of MoS₂. Here, we report an enhanced HER activity of MoS₂ by combing vertical nanosheets and H₂ annealing. Compared to horizontal MoS₂ nanosheets, pristine vertical MoS₂ nanosheets showed better HER activity due to a larger amount of edges. H₂ annealing further enhanced the HER activity of vertical MoS₂ nanosheets remarkably. Scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS) and electrochemical impedance spectroscopy (EIS) were used to elucidate the enhanced HER activity by H₂ annealing. SEM images showed that H₂ annealing roughened the MoS₂ edges, leading to more edge sites. XPS data revealed the smaller S : Mo ratio after H₂ annealing, meaning more S-vacancies. Meanwhile, EIS measurements showed that charge transfer was accelerated by H₂ annealing. These findings elaborated the H₂ annealing induced enhancement of the HER activity, which were further confirmed by the subsequent re-sulfurization experiment.

Vertical configuration and H₂ annealing enhanced the hydrogen evolution reaction activity of MoS₂ nanosheets.     

Facile synthesis of vacancy-induced 2H-MoS2 nanosheets and defect investigation for supercapacitor application

In this paper, a 2D molybdenum disulfide (MoS₂) nanosheet is prepared via a one-step hydrothermal method as electrode material for supercapacitors. Meanwhile, a series of MoS_2−x nanostructures with sulfur vacancies have been successfully obtained in an Ar/H₂ mixed atmosphere at different annealing temperatures. The prepared materials were characterized by XRD, HR-TEM, Raman and XPS to identify their morphology and crystal properties. MoS_2−x assembled by interconnected nanosheets (MoS_2−x-700) provides a maximum specific capacitance of 143.12 F g⁻¹ at a current density of 1.0 A g⁻¹ with 87.1% of initial capacitance reserved after 5000 cycles. The outstanding performance of the annealed MoS_2−x nanosheets in sodium storage is mainly attributed to the synergistic effect of the unique interconnected structure and the abundant active vacancy generated by the sulfur vacancies. Atomic models of sulfur vacancy defects on the basal plane, Mo-edge and S-edge were established and the electronic properties of MoS_2−x were further evaluated assisted by first principles theory. DFT calculation results show that sulfur vacancy defects can provide additional empty states near the Fermi level and induce unpaired electrons, thus increasing the carrier density and improving electrical conductivity. Our findings in this work provide experimental and theoretical evidence of improving the electrochemical performance of 2H-MoS₂ nanosheets by annealing treatment.

In this paper, a 2D molybdenum disulfide (MoS₂) nanosheet is prepared via a one-step hydrothermal method as electrode material for supercapacitors.     

Preconcentration and determination of trace Hg(ii) using ultrasound-assisted dispersive solid phase microextraction

Defect rich molybdenum disulfide (MoS₂) nanosheets were hydrothermally synthesized and their potential for ultrasound assisted dispersive solid phase microextraction of trace Hg(ii) ions was assessed. Ultrasonic dispersion allows the MoS₂ nanosheets to chelate rapidly and evenly with Hg(ii) ions and results in improving the precision and minimizing the extraction time. The multiple defect rich surface was characterized by X-ray diffraction and high-resolution transmission electron microscopy. The surface charge of intrinsically sulfur rich MoS₂ nanosheets and their elemental composition was characterized by zeta potential measurements, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. The cracks and holes on the basal planes of MoS₂ led to diffusion of the Hg(ii) ions into the interior channels. Inner-sphere chelation along with outer-sphere electrostatic interaction were the proposed mechanism for the Hg(ii) adsorption onto the MoS₂ surface. The experimental data showed good selectivity of MoS₂ nanosheets towards Hg(ii) adsorption. The systematic and constant errors of the proposed method were ruled out by the analysis of the Standard Reference Material (>95% recovery with <5% RSD). The Student''s t-test values for the analyzed Standard Reference Material were found to be less than the critical Student''s t value at 95% confidence level. The limit of detection (3S) was found to be 0.01 ng mL⁻¹. The MoS₂ nanosheets were successfully employed for the analysis of Hg(ii) in environmental water samples.

Hg(ii) ion adsorption onto an MoS₂ surface.     

Molecular dynamics study of the frictional properties of multilayer MoS2

To reveal the friction mechanism of molybdenum disulfide (MoS₂), the frictional properties of multilayer MoS₂ lubrication film were studied under variable loads and shearing velocities by the molecular dynamics (MD) method. The results showed irreversible deformation of MoS₂ was caused by heavy load or high shear velocity during the friction process and the interlayer velocity changed from a linear to a ladder-like distribution; thus, the number of shear surfaces and the friction coefficient decreased. The low friction coefficient caused by heavy load or high velocity could be maintained with a decrease in load or velocity. For a solid MoS₂ lubrication film, the number of shearing surfaces should be reduced as much as possible and the friction pair should be run under heavy load or high shear velocity for a period of time in advance; thus, it could exhibit excellent frictional properties under other conditions. The proposed friction mechanism provided theoretical guidance for experiments to further improve the frictional properties of MoS₂.

Deformation of MoS₂ layers directly leads to decrease in potential and ultimately leads to decrease in friction coefficient.