MoS2 Layers Research Articles

Strain Effect in the Layered MoS2-rGO Heterostructure with Enhanced Performance for Flexible Thermoelectric Applications

Strain Effect in the Layered MoS₂-rGO Heterostructure with Enhanced Performance for Flexible Thermoelectric Applications

In-Plane Bulk Photovoltaic Effect in a MoSe2/NbOI2 Heterojunction for Efficient Polarization-Sensitive Self-Powered Photodetection.

Two-dimensional ferroelectric materials can generate a bulk photovoltaic effect, making them highly promising for self-powered photodetectors. However, their practical application is limited by a weak photoresponse due to a weak transition strength and wide band gap. In this study, we construct a van der Waals heterojunction using NbOI2, which has significant in-plane polarization, with a highly absorbing MoSe2 layer. We observe ultrafast hole transfer from MoSe2 to NbOI2 within 0.4 ps and electron transfer in the opposite direction within 3.8 ps, facilitating efficient charge dissociation and extraction. Applying a direct current electric field poling modulates the ferroelectric domains in NbOI2, enhancing the bulk photovoltaic effect. This results in one of the highest responsivities for self-powered photodetectors (101.3 mA/W) at 0 V bias alongside excellent polarization sensitivity (∼7.58). This work advances the understanding of self-powering mechanisms via the bulk photovoltaic effect and proposes new strategies for future self-powered devices.

Insights into Interlayer Dislocation Augmented Zinc-Ion Storage Kinetics in MoS2 Nanosheets for Rocking-Chair Zinc-Ion Batteries with Ultralong Cycle-Life.

Increasing attention to sustainability and cost-effectiveness in energy storage sector has catalyzed the rise of rechargeable Zinc-ion batteries (ZIBs). However, finding replacement for limited cycle-life Zn-anode is a major challenge. Molybdenum disulfide (MoS2), an insertion-type 2D layered material, has shown promising characteristics as a ZIB anode. Nevertheless, its high Zn-ion diffusion barrier because of limited interlayer spacing substantiates the need for interlayer modifications. Here, N-doped carbon quantum dots (N-CQDs) are used to modify the interlayers of MoS2, resulting in increased interlayer spacing (0.8 nm) and rich interlayer dislocations. MoS2@N-CQDs attain a high specific capacity (258 mAh g-1 at 0.1 A g-1), good cycle life (94.5% after 2000 cycles), and an ultrahigh diffusion coefficient (10-6 to 10-8 cm2 s-1), much better than pristine MoS2. Ex situ Raman studies at charge/discharge states reveal that the N-CQDs-induced interlayer expansion and dislocations can reversibly accommodate the volume strain created by Zn-ion diffusion within MoS2 layers. Atomistic insight into the interlayer dislocation-induced Zn-ion storage of MoS2 is unveiled by molecular dynamic simulations. Finally, rocking-chair ZIB with MoS2@N-CQDs anode and a ZnxMnO2 cathode is realized, which achieved a maximum energy density of 120.3 Wh kg-1 and excellent cyclic stability with 97% retention after 15 000 cycles.

Can structure influence hydrovoltaic energy generation? Insights from the metallic 1T' and semiconducting 2H phases of MoS2.

Hydrovoltaic power generation from liquid water and ambient moisture has attracted considerable research efforts. However, there is still limited consensus on the optimal material properties required to maximize the power output. Here, we used laminates of two different phases of layered MoS2 - metallic 1T' and semiconducting 2H - as representative systems to investigate the critical influence of specific characteristics, such as hydrophilicity, interlayer channels, and structure, on the hydrovoltaic performance. The metallic 1T' phase was synthesized via a chemical exfoliation process and assembled into laminates, which can then be converted to the semiconducting 2H phase by thermal annealing. Under liquid water conditions, the 1T' laminates (having a channel size of ∼6 Å) achieved a peak power density of 2.0 mW m-2, significantly outperforming the 2H phase (lacking defined channels) that produced a power of 2.4 μW m-2. Our theoretical analysis suggests that energy generation in these hydrophilic materials primarily arises from electro-kinetic and surface diffusion mechanisms. These findings highlight the crucial role of phase-engineered MoS2 and underscore the potential of 2D material laminates in advancing hydrovoltaic energy technologies.

Optimizing CZTS Solar Cell Performance with Advanced Layer Configurations Using SCAPS Simulation

This research analyzes the modeling of CZTS (Copper Zinc Tin Sulfide) solar cells, with a focus on advanced layer configuration and thermal management to improve operational efficiency. Using SCAPS-1D software, this investigation seeks to augment cell efficiency by fine-tuning the dimensions of absorptive layers, modifying buffer compositions, and adjusting other critical components. The study evaluates the role of transition metal dichalcogenides (TMDs), specifically MoS₂ as the hole transport layer and ZnO as the window layer, in influencing open-circuit voltage (Voc) and short-circuit current density (Jsc). Furthermore, the research delves into temperature-related effects, demonstrating that elevated temperatures lead to a decrease in Voc and Jsc attributable to bandgap narrowing and heightened recombination processes. Through the optimization of the thicknesses of the CZTS, MoS₂, and WSe₂ layers, this study elucidates the manner in which material adjustments influence Voc, Jsc, fill factor (FF), and overall efficiency (η). In addition, effective thermal management emerges as a critical factor, given that increased temperatures elevate recombination rates, thereby adversely affecting FF and efficiency. The results of this study provide essential information for increasing the performance, durability and stability of CZTS solar cells under various environmental conditions.

Enhanced Aqueous Zinc-Ion Batteries Using 3D MoS2/Conductive Polymer Composite

MoS2, a typical transition metal dichalcogenide, features a layered structure, multi-phase transition, and tunable band gap, which is a promising candidate for aqueous zinc-ion batteries (AZIBs). Recent studies have focused on the metastable 1T-MoS2 phase, which exhibits superior electrical conductivity and electrochemical activity compared to the more stable 2H phase. Herein, a straightforward one-step hydrothermal method was used to synthesize three-dimensional MoS2/polymer composites (H-MoS2-PEDOT). Under acidic conditions, the polymerization and intercalation of EDOT molecules in the MoS2 layers promote the phase transition from 2H to 1T, thereby enhancing its conductivity and electrochemical performance. Additionally, it was found that the intercalated PEDOT and small amounts of water molecules have contributed to enhancing Zn2+ ion diffusion and cycle stability. As a result, AZIBs based on the H-MoS2-PEDOT composite deliver a high specific capacity of 173.6 mAh g−1 at 1 A g−1, maintaining a specific capacity of 116 mAh g−1 and a capacity retention of 82.8% after 1000 cycles at 5 A g−1.

Design of an Ultra-Highly Stable Lithium-Sulfur Battery by Regulating the Redox Activity of Electrocatalyst and the Growth of Lithium Dendrite through Localized Electric Field.

Polysulfide shuttling and dendrite growth are two primary challenges that significantly limit the practical applications of lithium-sulfur batteries (LSBs). Herein, a three-in-one strategy for a separator based on a localized electrostatic field is demonstrated to simultaneously achieve shuttle inhibition of polysulfides, catalytic activation of the Li-S reaction, and dendrite-free plating of lithium ions. Specifically, an interlayer of polyacrylonitrile nanofiber (PNF) incorporating poled BaTiO3 (PBTO) particles and coating with a layer of MoS2 (PBTO@PNF-MoS2) is developed on the PP separator. Theoretical calculations and experimental work show that the electric field generated at the membrane facilitates the fast and uniform transport of Li+ ions, thereby inhibiting dendrite growth. Additionally, the generated electric field promotes the MoS2 catalytic activity toward the Li-S redox reactions, particularly by reducing the reaction barriers for both the solid-liquid and solid-solid conversions. As a result, symmetrical Li//PBTO@PNF/PP/PBTO@PNF//Li cells demonstrate remarkable stability over 1200 h, and LSBs with a PP/PBTO@PNF-MoS2 composite separator maintain a specific capacity of 318.3 mA h g-1 after 4000 cycles at 2C, with an ultralow capacity decay rate of 0.015%. In addition, the PBTO@PNF membrane also enhances the mechanical flexibility and thermal stability of the composite separator.

Impact of MoS2 Layer Thickness and Donor Concentration on Saturation Current in 4-Layer MOSFET: A Comsol Simulation

This study investigates the effects of the thickness and donor concentration of a hybrid MoS2 semiconductor layer on the saturation current of a four-layer MOSFET, utilizing Comsol Multiphysics simulation software. By leveraging the software's capabilities to adjust physical parameters, we systematically analyze the influence of these variables on the device performance. Our findings indicate that increasing the MoS2 layer thickness and donor concentration significantly enhances the saturation current, thereby improving the overall efficiency of the four-layer MOSFET. These simulation results align closely with experimental data and create a robust foundation for future studies and fabrication efforts aimed at optimizing the performance of MOSFETs through material engineering.

Design and simulation of CsPb.625Zn.375IBr2-based perovskite solar cells with different charge transport layers for efficiency enhancement

In this work, CsPb.625Zn.375IBr2-based perovskite solar cells (PSCs) are numerically simulated and optimized under ideal lighting conditions using the SCAPS-1D simulator. We investigate how various hole transport layers (HTL) including Zn3P2, PTAA, MoS2, MoO3, MEH-PPV, GaAs, CuAlO2, Cu2Te, ZnTe, MoTe2, CMTS, CNTS, CZTS, CZTSe and electron transport layers (ETL) such as CdS, SnS2, ZnSe, PC60BM interact with the devices’ functionality. Following HTL material optimization, a maximum power conversion efficiency (PCE) of 16.59% was observed for the FTO/SnS2/CsPb.625Zn.375IBr2/MoS2/Au structure, with MoS2 proving to be a more economical option. The remainder of the investigation is done following the HTL optimization. We study how the performance of the PSC is affected by varying the materials of the ETL and to improve the PCE of the device, we finally optimized the thickness, charge carrier densities, and defect densities of the absorber, ETL, and HTL. In the end, the optimized arrangement produced a VOC of 0.583 V, a JSC of 43.95 mA/cm2, an FF of 82.17%, and a PCE of 21.05% for the FTO/ZnSe/CsPb.625Zn.375IBr2/MoS2/Au structure. We also examine the effects of temperature, shunt resistance, series resistance, generation rate, recombination rate, current-voltage (JV) curve, and quantum efficiency (QE) properties to learn more about the performance of the optimized device. At 300 K, the optimized device provides the highest thermal stability. Our research shows the promise of CsPb.625Zn.375IBr2-based PSCs and offers insightful information for further development and improvement.

Interfacial charge transfer on hierarchical synergistic shell wall of MXene/MoS2 on CdS nanospheres: heterostructure integrity for visible light responsive photocatalytic H2 evolution

Energy scarcity and environmental pollution have prompted research in hydrogen generation from solar to develop clean energy through highly efficient, effective, and long-lasting photocatalytic systems. Designing a catalyst with robust stability and an effective carrier separation rate was achieved through heterostructure assembly, but certain functionalities must be explored. In this paper we designed a ternary heterostructure assembly of CdS nanospheres wrapped with hierarchical shell walls of layered MXene-tagged MoS2 nanoflakes, forming intimate interfaces through an in-situ growth process. An in-layered shell wall of MXene with surface-wrapped MoS2 nanoflakes as a core–shell assembly improved the photo-corrosion resistance and accelerated the production of photocatalytic H2 (38.5 mmol g−1 h−1), which is 10.7, 3.1, and 1.9 times faster than that of CdS, CdS–MXe, and CdS–MoS2 nanostructures, respectively. The apparent quantum efficiency of the CdS–MXe2.4/MoS2 heterostructure was calculated to be 34.6% at λ = 420 nm. X-ray and ultraviolet photoelectron spectroscopies validated the electronic states, energy band alignment, and work function of the heterostructures, whilst time-resolved photoluminescence measured the carrier lifespan to evaluate the effective charge migration in the CdS-MXe/MoS2 heterostructure. The dual surface wrapping of MXe/MoS2 over CdS nanospheres confirmed the structural durability that remained intact throughout the photocatalytic reaction, promoting approximately 93.1% of its catalytic property even after five repeatable cycles. This study examined how the MXene heterostructure template improves the catalytic efficiency and opens a new way to design MXene-based durable heterostructure catalysts for solar-energy conversion.Graphical

Facile CVD Fabrication of Vertically Aligned MoS2 Nanosheets with Embedded MoO2 on Molybdenum for High-Performance Binder-Free Lithium-Ion Battery Anodes.

The demand for compact energy storage devices necessitates the development of high-performance anode materials directly integrated with current collectors, minimizing or eliminating the need for binders or additives. With its layered structure and high theoretical capacity, molybdenum disulfide (MoS2) is regarded as a promising anode material for lithium-ion batteries (LIBs). Here, we report chemical vapor deposition (CVD) growth of self-integrated, vertically aligned MoS2 nanosheets with embedded molybdenum dioxide (MoO2) directly on a molybdenum foil and explore its potential as an anode material for LIBs. The results show that the formation of the MoO2/MoS2 hybrid structure occurs through partial conversion of the initially grown MoO2 crystals to MoS2 layers under controlled sulfurization reactions. The self-integrated hybrid material, devoid of additional conductive or binder agents, exhibits remarkably efficient transfer of ions and electrons, facilitated by the high electrical conductivity of MoO2 and exposed active sites of MoS2. Electrochemical studies reveal an impressive areal capacity of 253 μA h cm-2 for the MoO2/MoS2 hybrid material on a molybdenum foil. In addition, the Li-ion diffusion coefficient value is estimated to be 0.798 × 10-10 and 1.14 × 10-10 cm2/s for the delithiation and lithiation processes, respectively. The capacity of LIBs can be significantly enhanced by engineering the MoO2/MoS2 anode material, making it a promising candidate for overcoming the limitations of single-anode materials. Our findings show that CVD can be a potential approach toward the fabrication of binder and conducting agent-free anodes directly on current collectors for advanced LIBs.

Room temperature polarization-resolved Raman and photoluminescence in uniaxially strained layered MoS2

Transition metal dichalcogenides (TMDCs) are one of the material systems of choice toward achieving room temperature quantum coherence. Externally applied strain is used as a more common control mechanism to tune electro-optical properties in TMDCs like molybdenum disulfide (MoS2). However, room temperature electron–phonon interactions in the presence of strain in transition metal dichalcogenides are still not fully explored. In this work, we employ uniaxial strain dependent Raman and photoluminescence (PL) studies on monolayer and bilayer MoS2 to explore electron–phonon physics. Helicity-resolved Raman in MoS2 obeys robust selection rules. Our studies reveal clear modification in these helicity-based selection rules in the presence of moderate uniaxial strain (ϵ = 0.4%–1.2%). The selection rules are restored upon clear symmetry breaking of the in-plane vibrational mode (ϵ > 1.2%). We assign these changes to the onset of Fröhlich interaction in this moderate strain regime. The changes in Raman scattering are accompanied by changes in valley selective relaxation observed through non-resonant photoluminescence (PL). The moderate strain regime also exhibits the onset of PL polarization for indirect excitonic emission under non-resonant excitation. Our experimental observations point toward electron–phonon coupling mechanisms affecting both valley-selective electron relaxation during PL emission as well as polarization-selective Raman scattering of two-dimensional semiconductors at room temperature.

Epitaxial growth and characterization of gan thin films on 2D MoS2 substrates via plasma-assisted molecular beam epitaxy

Gallium nitride (GaN) is an excellent material for high-performance optoelectronic and power electronic devices due to its superior thermal conductivity and exceptional electron transport properties. However, growing high-quality GaN films is challenging because of lattice mismatch and thermal expansion coefficient differences with conventional substrates like sapphire and silicon, resulting in threading dislocations and structural defects that compromise device performance. This study addresses these issues by utilizing a 2D-MoS₂ buffer layer, which provides an atomically smooth surface and quasi-van der Waals interface to minimize lattice mismatch stress and suppress defect propagation. GaN thin films were grown on MoS₂-deposited c-sapphire substrates using plasma-assisted molecular beam epitaxy (PA-MBE) under optimized conditions. The MoS₂ layer was prepared using a chemical vapor deposition process followed by nitridation. Characterization techniques, including Reflection High-Energy Electron Diffraction, Atomic Force Microscopy, Field Emission Scanning Electron Microscopy, and X-ray Diffraction, confirmed that the GaN films exhibited high crystallinity, phase purity, and preferred c-axis orientation, with minimal structural defects. Surface analysis showed moderate roughness, with a root mean square value of 11.35 nm, attributed to localized growth variations. The MoS₂ buffer layer significantly reduced lattice mismatch-induced stress, as indicated by the absence of secondary phases in XRD analysis and facilitated defect-free epitaxial growth. These findings demonstrate the transformative potential of combining PA-MBE with 2D material buffers to achieve high-quality GaN films. This approach holds promise for optoelectronic applications such as LEDs and laser diodes, as well as high-frequency electronic devices like high-electron-mobility transistors

Preparation and Adsorption Properties of a Three-Dimensional Superhydrophilic Mercury-Ion-Imprinted Polymer with Dual Recognition Site Based on MoS2/SBA-15.

Water pollution resulting from Hg(II) ions has garnered significant global concern for public health. The flexibility and simplicity of design, cost savings, and ease of operation with adaptive designs provide adsorption with a considerable advantage over other processes. However, MoS2 is hydrophobic in nature, which limits its efficiency in the removal of Hg(II) ions from water. Therefore, the incorporation of hydrophilic SBA-15 as supporting material, combined with a nanoflower-like layered MoS2 and its highly reactive exposed edges, produces hydrophilic properties that effectively eliminate Hg(II) from water . A mercury-ion-imprinted polymer (Hg(II)-IIP) was synthesized on the MoS2/SBA-15 surface using N-allylthiourea (ATU) as a functional monomer to enhance material selectivity and create dual recognition sites. Characterization investigation using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and water contact angle showed the successful synthesis of Hg(II)-IIP, excellent hydrophilicity, and close interaction between MoS2 and SBA-15. The maximum adsorption capacity of Hg(II)-IIP for Hg(II) under optimized adsorption conditions was 567.78 mg·g-1 in 90 min, which was 6 times greater than that of the IIP solely based only on SBA-15, and followed by pseudo-second-order and aligned more closely fits with the Langmuir adsorption isotherm. Furthermore, the adsorption capacity of the synthesized Hg(II)-IIP was greater than that of three other common monomers IIP. Hg(II)-IIP possesses a strong ability to regenerate, while also showing better selectivity for Hg(II) in the presence of other interfering ions, indicating its robust anti-interference capability in the multivariate mixed solution. The analysis of the actual sample indicated that Hg(II)-IIP attained recoveries between 97.92 and 100.28% in water samples. Theoretical calculations using density functional theory (DFT) and frontier molecular orbital (FMO) indicated that the binding energy of the sulfur atom forming a tetra-ligand with Hg(II) on ATU was 0.6511 eV greater than that of a diligand. The energy gap was determined to be 0.1550 eV, supporting the preference for S-Hg tetra-ligand adsorption.

Soft Sputtering of Large-Area 2D MoS2 Layers Using Isolated Plasma Soft Deposition for Humidity Sensors.

2D transition-metal dichalcogenides are emerging as key materials for next-generation semiconductor technologies owing to their tunable bandgaps, high carrier mobilities, and exceptional surface-to-volume ratios. Among them, molybdenum disulfide (MoS2) has garnered significant attention. However, scalable wafer-level deposition methods that enable uniform layer-controlled synthesis remain a critical challenge. In this paper, a novel fabrication approach-isolated plasma soft deposition (IPSD) followed by sulfurization-for the scalable production of 2D MoS2 with precise layer control is introduced. The IPSD system employs a scanning-based deposition method combined with plasma surface pretreatment, achieving large-area, high-quality 2D MoS2 layers. Comprehensive characterizations using Raman, UV-vis, and photoluminescence spectroscopy, and transmission electron microscopy confirmed the successful synthesis of crystalline mono- to tetralayer 2D MoS2 on 6-inch SiO2/Si substrates. Furthermore, respiration sensors fabricated using the IPSD-grown 2D MoS2 layers demonstrated fast response times (≈1 s) and high response to relative humidity levels between 30% and 60%. This study offers significant advancements in the scalable synthesis of 2D MoS2 and opens new avenues for its application in advanced sensing and electronic devices.

Insulator Material Deposited with Molybdenum Disulphide Prospective for Sensing Application.

Two-dimensional molybdenum disulfide (MoS2) exhibits interesting properties for applications in micro and nano-electronics. The key point for sensing properties of a device is the quality of the material's surface. In this study, MoS2 layers were deposited on polymers by pulsed laser deposition (PLD). This process was monitored by a mass quadrupole spectrometer to record the emissions of MoS2 and evaluate the amount of molybdenum and sulfur compounds generated. The changes in laser parameters during the PLD strongly affect the properties of the formed MoS2 film. The exploration of the composition and structure of the films was followed by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR), Atomic Force Microscopy (AFM), and mass quadrupole spectrometer (MQS). The possible application of the fabricated composite as a sensor is preliminarily considered.

Tribological Properties of SPS Reactive Sintered Al/MoS2 Composites

In search of opportunities to improve mechanical properties and abrasion resistance, composites based on aluminum reinforced with MoS2 particles were produced. The authors’ previous research indicated the possibility of obtaining hard dispersion precipitates of the Al12Mo intermetallic phase as a result of the reaction of the composite components at a temperature exceeding 550 °C during the SPS (Spark Plasma Sintering) process. This work focused on optimizing the SPS consolidation process and assessing the microstructure and mechanical properties of the obtained materials. A series of experiments proved that by increasing the amount of the strengthening phase and increasing the process temperature, a significant amount of Al12Mo and Al5Mo strengthening phases is produced. Exceptionally good dispersion of reinforcing particles and the presence of layered MoS2 crystals, while ensuring optimal parameters of the synthesis process, lead to a change in friction mechanisms and improved abrasion resistance through an approximately 30-fold decrease in the wear factor.

Development of the Electrode for All-Solid-State Lithium Rechargeable Batteries Using MoS2 by Liquid Phase Mixing

１． Purpose Rechargeable batteries using inorganic solid electrolytes are currently attracting attention from many quarters as next-generation rechargeable batteries because they can use lithium metal (3860 mAh g-1), which has a large theoretical capacity, as the negative electrode due to its ability to suppress dendrites, and can operate at high temperatures. MoS2, a transition metal dichalcogenite, has a layered structure consisting of sheets of MoS2, which has been studied as a cathode active material because of its extremely high theoretical capacity (670 mAh g-1 , 3390 mAh cm-3) and relatively low cost. In the case of liquid electrolytes, electrodes with MoS2 crystals grown on graphene by a hydrothermal method have been developed to prevent re-lamination of MoS2 and to ensure conductivity(1), but there were problems such as a small bulk density of active material and a very complicated electrode fabrication method. In contrast, we thought that the issues of preventing re-lamination and ensuring conductivity could be solved by using an inorganic solid electrolyte with a structure in which solid electrolyte and conductivity aids are sandwiched between single to several layers of MoS2 and MoS2 particles. In this method, the bulk density of the active material can be freely selected, and electrode fabrication becomes relatively easy. Therefore, in this study, electrodes were fabricated using single~several layers of MoS2 solvated in a solvent in order to fabricate electrodes while preventing re-lamination. The solid electrolyte (Li3PS4) used for mixing was also synthesized by the liquid-phase method, and the electrodes were prepared only by liquid-phase mixing, which is advantageous for industrialization. ２． experiment MoS2 (1.0 g) and butyl lithium-hexane solution (2.0 M, 25 mL) were mixed, and MoS2@Li powder was obtained by inserting lithium atoms between layers of MoS2 by irradiating with bath-type ultrasound for 3 hours. MoS2@Li was then exfoliated and dispersed by ultrasonic homogenization in butyl acetate solvent for 20 minutes to prepare MoS2 dispersion.For electrode preparation, MoS2 dispersion, conductive auxiliary material (vapor-grown carbon fiber), solid electrolyte (Li3PS4 dispersion solution), and zirconia balls (φ4 mm, 20 g) were mixed by shaking at 1500 rpm for 10 minutes. The solvent was then removed by centrifugation and decantation, vacuum dried for 48 hours, and annealed at 100 °C for 2 hours. The Li3PS4 dispersion solution was synthesized in advance by a liquid-phase method using butyl acetate as solvent. The cell was fabricated using amorphous Li3PS4 synthesized by a mechanochemical method as the electrolyte and a Li/In alloy as the reference electrode and anode, and combined with the above cathode to form a two-pole cell. ３． Results and discussion Transmission electron microscope images of the MoS2 dispersion used to fabricate the electrode are shown in Fig. 1. As a result, it was confirmed that MoS2 of about several hundred nm was present in the dispersion solution in a single to several layer state, and that single to several layers of MoS2 were dispersed in the solvent.The charge-discharge curves of electrodes with exfoliated and untreated MoS2 are shown in Fig. 2. A charge plateau was observed at approximately 2.2 V for both electrodes. Multiple plateaus were observed during the discharge process, confirming that several types of reactions were occurring in a multi-step manner. No reduction reaction was observed at 2.5 to 4.5 V. The electrode made of untreated MoS2 had a discharge capacity of about 500 mAh g-1, whereas the electrode made of exfoliated MoS2 showed a very high discharge capacity of 1105 mAh g-1, more than twice the maximum. The Cyclic voltammograms of electrodes with exfoliated and untreated MoS2 are shown in Fig. 3. The CV measurements have peaks at similar positions for these electrodes, and the electrodes with exfoliated MoS2 showed higher current values overall. These results suggest that the reaction mechanism is almost the same for these electrodes, and that the utilization of MoS2 was improved by using stripped MoS2.(References)(1) Liu , K.Jia , J.Yang , S.He , Z.Liu , X.Wang , J.Qiu Chem.Eng.J 475,146181(2023) Figure 1

(Invited) Integration and Optimization of 2D Transition Metal Dichalcogenides as Switching Layers in Memristors

Memristive devices possess the ability to dynamically adjust resistance based on previous voltage and current inputs. They represent a frontier in next-generation computational hardware, offering unparalleled potential for brain-inspired computing and neuromorphic engineering. Among the various configurations, electrochemical metallization (ECM) memristors feature a solid electrolyte layer sandwiched between two electrodes and perform resistive switching via filament formation (SET) and dissolution (RESET) [1]. Recent studies have focused on the integration of two-dimensional (2D) materials into the design of ECM memristors, aiming at improving performance and unlocking new functionalities [2-4]. 2D transition metal dichalcogenides and hexagonal boron nitride, in particular, are promising candidates for realizing memristors with ultra-low switching voltages, suitable for neuromorphic computing and artificial synapses [5, 6].In this talk, I will focus on vertical ECM memristor in crossbar configuration using chemical vapor deposited (CVD), atomic-thick MoSe2 as switching material, and Au/Cu as bottom/top electrodes. The devices exhibit nonvolatility and bipolar resistive switching behavior, with well-defined SET/RESET voltages (below 1V in absolute value) [7]. We performed atomic-scale investigations by transmission electron microscopy to unveil the filament formation mechanism within the MoSe2 layer. Our results shed light on the Cu/MoSe2 interface, particularly critical for memristor performance, providing key information on the intermixing and diffusion mechanisms of Cu atoms within the device structure.Furthermore, we studied the effect of XeF2 fluorination of the MoSe2 films to tune their surface properties and improve the ion transport kinetics across the interface with Cu. By carefully controlling the XeF2 process, we were able to induce structural and chemical modifications in the MoSe2, such as layer thinning and doping/implantation. This could provide a way of controlling the interface morphology and ultimately the performance and reliability of the memristive devices. Transport properties and X-ray photoelectron spectroscopy analyses provided insights into the fluorination-induced modifications on the MoSe2 surface, offering a framework for performance optimization. Overall, these findings rationalize the 2D materials-based ECM memristor operation and highlight the potential for advanced applications.

Operando Electrochemical Raman Spectroscopy Studies of Working Electrodes in (photo)Electrocatalytic Water Splitting

Raman spectroscopy has been applied as a vibrational spectroscopic technique in the field of chemical, materials, and life sciences. Recently, the operando electrochemical Raman spectroscopy has received more research attention for the characterizations of working electrodes in (photo)electrochemical catalysis. This technique allows for the characterization of the fate of electrocatalysts on the surface of the working electrodes under electrochemical reaction conditions, which is crucial to determine the chemical identify of the electrocatalysts.We apply the operando electrochemical Raman spectroscopy to study the anodes and cathodes in the (photo)electrocatalytic water splitting process, which is an important process to generate the clean energy hydrogen (H2) gas from water using solar energy and electricity. Specifically, we study the stability of the electrocatalyst molybdenum sulfide (MoS2) on silicon (Si) photocathode for the hydrogen evolution reaction (HER) and the electrochemical transformation of the electrocatalyst cobalt hydroxide (Co(OH)2) on nanostructured gold (Au) photoanode for the oxygen evolution reaction (OER). We have identified the correlation between the morphological changes and vibrational features of the MoS2 layer and detected the potential-dependent vibrational features of the Co(OH)2 film.