Transition Metal Chalcogenides Research Articles

Atomically substitution engineering of europium-based dichalcogenides for enhancing tailored properties and superior applications

Transition-metal chalcogenides can be used as photoconductors and in optoelectronic devices. Research on the electronic properties of KBaSbSe3 has established that the parental compound possesses an indirect band gap of 2.0 eV. By europium doping, the material’s band structure experienced a transformation, resulting in a direct semiconducting behavior. This change was observed in spin-up and spin-down polarizations, with a bandgap of 1.5 eV. An analysis of the electron charge density (ECD) contour of the (101) crystallographic plane has been conducted to examine the bonding characteristics. Based on the reflectivity spectra, it is evident that both compounds exhibit a significant level of reflectivity, making them potentially suitable for shielding against visible and UV radiation. The calculations of birefringence demonstrate the ability to achieve phase matching for both observed compounds. Calculations were performed using Boltzmann transport theory to determine the Seebeck coefficient, Hall coefficient, electrical and thermal conductivities, and figure of merit. The compound KBaSbSe3 exhibits N-type at low temperatures and P-type due to a change in the Seebeck coefficient. Both compounds have excellent optical and thermal responses, making them promising materials for optoelectronic and thermoelectric devices.

Defect-mediated structural phase transition in Ta2NiSe5 visualized via in situ TEM

Extensive experimental and theoretical efforts have been devoted to elucidating the origin of either structural or electronic instability in the formation of excitonic state in Ta2NiSe5, whereas the effects of lattice defects on actual structural phase transition in Ta2NiSe5 remain elusive. Here, we perform in situ transmission electron microscopy (TEM) experiments to investigate the structural phase transition of Ta2NiSe5 thin films, with a particular focus on the influence of microstructural features and lattice defects on the phase transition. In the cyclic in situ heating-cooling TEM experiments, we track the reversible orthorhombic to monoclinic (vice versa) phase transitions via twinning variant contrast in TEM images and via changes in reflection splitting in diffraction patterns. We further investigate the effects of dislocations and grain boundaries on the phase transition of Ta2NiSe5 thin films. Our findings reveal that individual dislocations can inhibit the transition from monoclinic to orthorhombic phases while simultaneously promoting the reverse transition from orthorhombic to monoclinic phases. Furthermore, we observe a phenomenon of metastable to stable phase transition within grain-boundary-confined regions of Ta2NiSe5 thin films. These in situ TEM observations offer a comprehensive microscopic perspective on defect-mediated phase transitions in Ta2NiSe5. This insight may extend to other varieties of transition-metal chalcogenides, thus implying a broader applicability.

Multiscale structural engineering of Co0.85Se@porous carbon composite enables highly reversible lithium/sodium storage

Cobalt selenide (Co0.85Se) has been regarded as the most potential anode material for both lithium/sodium ion batteries (LIBs and SIBs) due to its high specific capacity and excellent pseudocapacitive effect. However, the inevitable volume expansion during conversion reaction and grievous dissolution of Se in electrolytes seriously undermine its reversibility and cycling stability. Combining the transition-metal chalcogenides with stable porous carbon networks is considered as one of the most effective strategies to improve electrochemical stability and conductivity of transition-metal chalcogenides. Here, we proposed a multiscale structural engineering strategy to encapsulate selenide nanoparticles in N-doped porous carbon to enable high-performance Co0.85Se@porous carbon composite for highly reversible lithium/sodium storage. Specifically, the Co0.85Se nanoparticles are tightly anchored to carbon network through substantial SeC bond, which effectively buffer volume expansion and inhibit the dissolution of Se in electrolytes. Additionally, the carbon pores with multilevel size help achieving the fast ions diffusion. The unique structure enables the Co0.85Se composite anode to exhibit excellent discharge capacities of 955.1 mAh g−1 at 100 mA g−1 after 100 cycles, 305.6 mAh g−1 at 1 A g−1 of full cells after 550 cycles in LIBs and 491.3 mAh g−1 at 100 mA g−1 after 100 cycles in SIBs.

Modification of NiSe2 Nanoparticles by ZIF-8-Derived NC for Boosting H2O2 Production from Electrochemical Oxygen Reduction in Acidic Media

The two-electron oxygen reduction reaction (2e− ORR) has emerged as an attractive alternative for H2O2 production. Developing efficient earth-abundant transition metal electrocatalysts and reaction mechanism exploration for H2O2 production are important but remain challenging. Herein, a nitrogen-doped carbon-coated NiSe2 (NiSe2@NC) electrocatalyst was prepared by successive annealing treatment. Benefiting from the synergistic effect between the NiSe2 nanoparticles and NC, the 2e− ORR activity, selectivity, and stability of NiSe2@NC in 0.1 M HClO4 was greatly enhanced, with the yield of H2O2 being 4.4 times that of the bare NiSe2 nanoparticles. The in situ Raman spectra and density functional theory (DFT) calculation revealed that the presence of NC was beneficial for regulating the electronic state of NiSe2 and optimizing the adsorption free energy of *OOH, which could enhance the adsorption of O2, stabilize the O-O bond, and boost the production of H2O2. This work provides an effective strategy to improve the performance of the transition metal chalcogenide for 2e− ORR to H2O2.

Construction of Co-Se-W at Interfaces of Phase-Mixed Cobalt Selenide via Spontaneous Phase Transition for Platinum-Like Hydrogen Evolution Activity and Long-Term Durability in Alkaline and Acidic Media.

Cost-effective transition metal chalcogenides are highly promising electrocatalysts for both alkaline and acidic hydrogen evolution reactions (HER). However, unsatisfactory HER kinetics and stability have severely hindered their applications in industrial water electrolysis. Herein, a nanoflowers-shaped W-doped cubic/orthorhombic phase-mixed CoSe2 catalyst ((c/o)-CoSe2-W) is reported. The W doping induces spontaneous phase transition from stable phase cubic CoSe2 (c-CoSe2) to metastable phase orthorhombic CoSe2, which not only enables precise regulation of the ratio of two phases but also realizes W doping at the interfaces of two phases. The (c/o)-CoSe2-W catalyst exhibits a Pt-like HER activity in both alkaline and acidic media, with record-low HER overpotentials of 29.8mV (alkaline) and 35.9mV (acidic) at 10mAcm-2, respectively, surpassing the vast majority of previously reported non-precious metal electrocatalysts for both alkaline and acidic HER. The Pt-like HER activities originate from the formation of Co-Se-W active species on the c-CoSe2 side at the phase interface, which effectively modulates electron structures of active sites, not only enhancing H2O adsorption and dissociation at Co sites but also optimizing H* adsorption to ΔGH*≈0 at W sites. Benefiting from the abundant phase interfaces, the catalyst also displays outstanding long-term durability in both acidic and alkaline media.

Edge-Rich 3D Structuring of Metal Chalcogenide/Graphene with Vertical Nanosheets for Efficient Photocatalytic Hydrogen Production.

Constructing pertinent nanoarchitecture with abundant exposed active sites is a valid strategy for boosting photocatalytic hydrogen generation. However, the controllable approach of an ideal architecture comprising vertically standing transition metal chalcogenides (TMDs) nanosheets on a 3D graphene network remains challenging despite the potential for efficient photocatalytic hydrogen production. In this study, we fabricated edge-rich 3D structuring photocatalysts involving vertically grown TMDs nanosheets on a 3D porous graphene framework (referred to as 3D Gr). 2D TMDs (MoS2 and WS2)/3D Gr heterostructures were produced by location-specific photon-pen writing and metal-organic chemical vapor deposition for maximum edge site exposure enabling efficient photocatalytic reactivity. Vertically aligned 2D Mo(W)S2/3D Gr heterostructures exhibited distinctly boosted hydrogen production because of the 3D Gr caused by synergetic impacts associated with the large specific surface area and improved density of exposed active sites in vertically standing Mo(W)S2. The heterostructure involving graphene and TMDs corroborates an optimum charge transport pathway to rapidly separate the photogenerated electron-hole pairs, allowing more electrons to contribute to the photocatalytic hydrogen generation reaction. Consequently, the size-tailored heterostructure showed a superior hydrogen generation rate of 6.51 mmol g-1 h-1 for MoS2/3D graphene and 7.26 mmol g-1 h-1 for WS2/3D graphene, respectively, which were 3.59 and 3.76 times greater than that of MoS2 and WS2 samples. This study offers a promising path for the potential of 3D structuring of vertical TMDs/graphene heterostructure with edge-rich nanosheets for photocatalytic applications.

Enhancing Stability and Activity of Transition Metal Chalcogenides: Development of Carbon-Based Hydrochar Supported Nickel-Cobalt Selenide Electrocatalyst for Oxygen Evolution Reaction

Transition metal chalcogenides (TMCs) have been utilized as cost-effective alternatives for noble metal electrocatalysts, exhibiting comparable activity in the oxygen evolution reaction (OER). Nickel-cobalt selenide (NiCoSe) is a TMC exhibiting significant potential in reducing the overpotential of the oxygen evolution reaction (OER). A carbon-based hydrochar support is used as a scaffold for depositing NiCoSe, ensuring the dispersion and stability of the synthesized electrocatalyst. This work develops a NiCoSe/hydrochar electrocatalyst to enhance the stability and activity of the TMC towards OER. Various compositions of nickel-cobalt selenide (NiCoSe2, Ni0.85Co0.85Se, and Ni0.6Co0.4Se2) with a chitin-based hydrochar support are synthesized. The electrocatalytic activity is determined using cyclic voltammetry (CV) and linear sweep voltammetry using a three-electrode set-up. NiCoSe2 has the lowest overpotential at 179.3 mV and a Tafel slope of 163.4 mV-dec-1. This highlights the enhanced performance of NiCoSe2 compared to other compositions.

N-doped 3D carbon encapsulating nickel selenide nanoarchitecture with cation defect engineering: An ultrafast and long-life anode for sodium-ion batteries

Transition metal chalcogenides (TMCs) hold great potential for sodium-ion batteries (SIBs) owing to their multielectron conversion reactions, yet face challenges of poor intrinsic conductivity, sluggish diffusion kinetics, severe phase transitions, and structural collapse during cycling. Herein, a self-templating strategy is proposed for the synthesis of a class of metal cobalt-doped NiSe nanoparticles confined within three-dimensional (3D) N-doped macroporous carbon matrix nanohybrids (Co-NiSe/NMC). The cation defect engineering within the developed Co-NiSe and 3D N-doped carbon plays a crucial role in enhancing intrinsic conductivity, reinforcing structural stability, and reducing the barrier to sodium ion diffusion, which are verified by a series of electrochemical kinetic analyses and density functional theory calculations. Significantly, such cation defect engineering not only reduces overpotential but also accelerates conversion reaction kinetics, ensuring both exceptional high-rate capability and extended durability. Consequently, the optimally engineered Co-NiSe/NMC demonstrates a remarkable rate performance, delivering 390 mAh g−1 at 10 A g−1. Moreover, it exhibits an unprecedented lifespan, maintaining a remarkable capacity of 403 mAh g−1 after 1400 cycles and 318 mAh g−1 after 4000 cycles, even at high rates of 1.0 and 2.0 A g−1, respectively. This work marks a substantial advancement in achieving both high performance and prolonged cycle life in sodium-ion batteries.

Chemiresistive Materials for Alcohol Vapor Sensing at Room Temperature

The development of efficient sensors able to detect alcoholic compounds has great relevance in many fields including medicine, pharmaceuticals, food and beverages, safety, and security. In addition, the measurements of alcohols in air are significant for environmental protection because volatile alcohols can have harmful effects on human health not only through ingestion, but also through inhalation or skin absorption. The analysis of alcohols in breath is a further expanding area, being employed for disease diagnoses. The analyses performed by using chromatography, mass-spectrometry, nuclear magnetic resonance, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, or Raman spectroscopy often require complex sampling and procedures. As a consequence, many research groups have focused their efforts on the development of efficient portable sensors to replace conventional methods and bulky equipment. The ability to operate at room temperature is a key factor in designing portable light devices suitable for in situ real-time monitoring. In the present review, we provide a survey of the recent literature on the most efficient chemiresistive materials for alcohol sensing at room temperature. Remarkable gas-sensing performances have mainly been obtained by using metal oxides semiconductors (MOSs), metal organic frameworks (MOFs), 2D materials, and polymers. Among 2D materials, we mainly consider graphene-based materials, graphitic carbon nitride, transition metal chalcogenides, and MXenes. We discuss scientific advances and innovations published in the span of the last five years, focusing on sensing mechanisms.

Study on oxygen evolution reaction efficiency demonstrated by Ce-E (E = S, Se and te) electrocatalyst

The strategy of generating sustainable energy with hydrogen fuel is highly significant and promising. Hydrogen fuel being non-toxic proves beneficial for the environment and can be produced in a variety of ways, as industrial water splitting into oxygen and hydrogen is a crucial future plan. This study aims to investigate cerium-based chalcogens (CeS, CeSe, and CeTe), as a catalyst to broaden the family of highly effective OER electrocatalysts based on transition metal chalcogenides. CeTe on NF was found to exhibit lowest onset potential with an overpotential of 333 mV at 10 mAcm−2 and a 51 mVdec−1 Tafel value among CeE (E = S, Se) chalcogenides with comparable stoichiometry. Using different analyses, it was determined that CeTe had a large surface area of 83.7 m2g-1, a cubic structure, and a highly crystalline nanoflakes morphology. High electrochemical surface area of 562 cm2, small resistance as Rs of 1.12 Ω, and Rct 729 mΩ, along with high TOF value of 0.174 s−1, 0.059 s−1, 0.009 s−1 for CeTe as compared to CeSe and CeS have supported by CV results. In particular, CeTe showed exceptional catalytic efficiency and was highly active and durable in oxygen evolution reactions.

Magnetic and thermoelectric properties of quasi-one-dimensional BaVSe3

Quasi-one-dimensional (Q1D) materials possess extraordinary magnetic and transport characteristics, which render them of critical importance. In this study, we present the synthesis of phase pure Q1D BaVSe3 via a novel heat treatment process and analyze its low-temperature thermoelectric, magnetotransport, and magnetic properties. A comparison is made between this phase pure system and the BaVSe3 infused with the secondary BaSe3 phase that we previously reported todetermine the potential effect of impurities on the magnetic and thermoelectric properties. Our previous study covered the experimental and theoretical investigation on the exotic magnetic properties of BaVSe3 with BaSe3. In phase pure BaVSe3, at TC ∼ 41.2 K, a paramagnetic to ferromagnetic transition with a magnetic moment of 1.74 μB from V4+ was observed,consistent with calculated values. At very low temperatures (<117 K), the material behaved like glass, showed Griffiths-like behaviorand spin valve-like butterfly magnetoresistance (BMR). Experiments indicate that these exotic magnetic properties are caused by the interaction between the A1g and t2g levels of the V 3d orbital and their spin orientation. Magnetic frustration in these materials is caused by V-V inter and intra chain interactions in the 1D spin chains of V. Q1D BaVSe3 (BVS) demonstrated n-type thermoelectricity with a thermoelectric figure of merit of ∼ 0.008, 4 × greater than BaVSe3:BaSe3 (BVS: BS) at room temperature. The thermal transport is determined to be primarily phonon-dependent. The magnetic property studies disclosed that this FM transition metal chalcogenide can contribute to low-temperature spintronics.

Computational analysis of ternary cation perovskite based solar cells employing transition metal chalcogenide, graphene derivatives, and SWCNT as hole transport layers

In this study, a numerical modelling on device configurations composed of Cs3Bi2I9 as the absorber material is performed by choosing diverse hole transport layers (HTLs) such as Cu2Te, graphene oxide (GO), reduced graphene oxide (rGO) and single walled carbon nanotube (SWCNT). All device configurations exhibit excellent PCE when the design parameters of perovskite, charge transport materials are optimized. The PCE of the device configurations with Cu2Te, GO, rGO and SWCNT as HTL is estimated as 10.81%, 10.87%, 9.99% and 11% respectively on optimizing design parameters of layers of the device. The perovskite solar cell (PSC) design is further optimized for suitable back metal contact and the device with rGO as the HTL shows an enhancement in PCE from 9.99% to 11.62% when Au is replaced by Se with a work function of 5.9 eV. Among the device configurations with distinct HTLs analysed, the FTO/ZnO/Cs3Bi2I9/rGO/Se configuration achieves the maximum PCE of 11.62%, indicating that rGO is the most suitable HTL material among the chosen ones. All modelled devices exhibit a gradual decline in PCE with temperature, except the PSC with SWCNT as the HTL, which shows a sudden performance degradation with temperature.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing.

Direct Laser Writing (DLW) has been increasingly selected as a microfabrication route for efficient, cost-effective, high-resolution material synthesis and conversion. Concurrently, lasers participate in the patterning and assembly of functional geometries in several fields of application, of which electronics stand out. In this review, recent advances and strategies based on DLW for electronics microfabrication are surveyed and outlined, based on laser material growth strategies. First, the main DLW parameters influencing material synthesis and transformation mechanisms are summarized, aimed at selective, tailored writing of conductive and semiconducting materials. Additive and transformative DLW processing mechanisms are discussed, to open space to explore several categories of materials directly synthesized or transformed for electronics microfabrication. These include metallic conductors, metal oxides, transition metal chalcogenides and carbides, laser-induced graphene, and their mixtures. By accessing a wide range of material types, DLW-based electronic applications are explored, including processing components, energy harvesting and storage, sensing, and bioelectronics. The expanded capability of lasers to participate in multiple fabrication steps at different implementation levels, from material engineering to device processing, indicates their future applicability to next-generation electronics, where more accessible, green microfabrication approaches integrate lasers as comprehensive tools.

Precise Layer-by-Layer Assembly of Dual Quantum Dots Artificial Photosystems Enabling Solar Water Oxidation.

Quantum dots (QDs) colloidal nanocrystals are attracting enduring interest by scientific communities for solar energy conversion due to generic physicochemical merits including substantial light absorption coefficient, quantum confinement effect, enriched catalytically active sites, and tunable electronic structure. However, photo-induced charge carriers of QDs suffer from ultra-short charge lifespan and poor stability, rendering controllable vectorial charge modulation and customizing robust and stable QDs artificial photosystems challenging. Herein, tailor-made oppositely charged transition metal chalcogenides quantum dots (TMCs QDs) and MXene quantum dots (MQDs) are judiciously harnessed as the building blocks for electrostatic layer-by-layer assembly buildup on the metal oxides (MOs) framework. In these exquisitely designed LbL assembles MOs/(TMCs QDs/MQDs)n heterostructured photoanodes, TMCs QDs layer acts as light-harvesting antennas, and MQDs layer serves as electron-capturing mediator to relay cascade electrons from TMCs QDs to the MOs substrate, thereby yielding the spatially ordered tandem charge transport chain and contributing to the significantly boosted charge separation over TMCs QDs and solar water oxidation efficiency of MOs/(TMCs QDs/MQDs)n photoanodes. The relationship between interface configuration and charge transfer characteristics is unambiguously unlocked, by which photoelectrochemical mechanism is elucidated. This work would provide inspiring ideas for precisely mediating interfacial charge transfer pathways over QDs toward solar energy conversion.

CVT grown CuSe single crystals: Unveiling photodetection advancements and thermoelectric promise

Over the past few decades, transition metal chalcogenides garnered global recognition for their noteworthy contributions to the modeling and engineering of electronic, optoelectronic, and thermoelectric devices to improve overall device performance. In the current investigation, the first ever growth of CuSe single crystals is achieved utilizing the chemical vapor transport technique with iodine serving as a transporting medium. The ascertainment of the hexagonal unit cell configuration in the grown CuSe crystals with the P63/mmc space group is substantiated via powder X-ray diffraction examination. The micro-surface characteristics exhibited planar facets outlined by layer boundaries, signifying crystal development through a mechanism reliant on layer growth. The direct optical bandgap of 1⋅64 eV for CuSe single crystals is unveiled by optical reflectance spectrum, demonstrating its aptitude for incorporation into photodetectors. The Raman spectrum manifested a prominent peak at 259 cm−1, aligning to Ag1 vibrational mode. The exploration of temperature-induced fluctuations in the power factor and figure of merit unveiled a progressive increase with rising temperatures. The optimal ZT parameter for the CuSe single crystals attains 0⋅058 at 523 K. The thermogravimetric patterns of CuSe single crystals exhibited singular step decomposition, exemplified by an average weight reduction of 25⋅49 % across the temperature spectrum from ambient to 813 K. The current−voltage (I–V) features of the fabricated CuSe single crystal photodetector are assessed under biasing voltage set at 20 mV at ambient temperature. Under a bias voltage of 20 mV and a polychromatic light intensity of 50 mW/cm2, the achieved responsivity is 4335⋅57 μA/W and a detectivity of 135 × 106 Jones. The photoresponse and thermoelectric examination of CuSe crystals alludes to their potential utility in innovative applications on the horizon.

Enhanced field emission characteristics of WS2 nano-films by diamond film and Mo film

WS2 is a type of transition metal chalcogenide materials (TMDCs) that exhibits exceptional photoelectric properties. Due to its atomically sharp edges, WS2 has the capability to enhance the electric field around its edges, thus presenting significant potential in field emission applications. In this study, the electron beam vapor deposition (EBVD) system and microwave plasma chemical vapor deposition (MPCVD) system were used to prepare a series of single-layer WS2 films，single-layer diamond films and diamond/WS2 nano-composite films on N-type highly doped Si substrate, and Mo/WS2 nano-composite films were prepared on Al2O3 ceramic substrate. Based on the characterization and analysis of the microstructure and chemical composition of each thin film layer in the above film devices, the field emission (FE) characteristics of each thin film device are compared and studied. The results demonstrate that the maximum FE current density of diamond/WS2 nano-composite film device is 912 μA/cm2, which is 2.7 times of the maximum FE current density of Mo/WS2 nano-composite film device 330 μA/cm2, and 3.4 times of the maximum FE current density of the single-layer diamond thin film device 267 μA/cm2. The single layer WS2 film did not exhibit measurable FE performance. The working principles of thin film field emission devices with various structures are introduced. It is considered that the diamond layer plays the role of electron accelerating layer, which not only effectively improves the FE characteristics of diamond/WS2 nanocomposite film, but also improves the repeatability and long-term stability of diamond/WS2 nanocomposite film FE devices.

Structural, elastic, mechanical, and electronic properties of chalcogenide perovskite SnZrS3 under pressure

In this paper, we have presented the structural, elastic, mechanical, and electronic properties of the transition metal chalcogenide perovskite SnZrS3 under different pressures by using first-principles method. Our calculated lattice parameters at ambient pressure are in good agreement with the experimental and previous theoretical results. The elastic constants were evaluated numerically for orthorhombic SnZrS3 using the strain-stress approach. Orthorhombic SnZrS3 shows a strong anisotropic behavior of the elastic and structural properties. According to the calculations of the electronic properties, we find the states near the valence band top are derived from S 3p, Zr 4d, Sn 5p, and Sn 5s orbitals, and the lowest conduction band is composed of Zr 4d, S 3p, and Sn 5p orbitals. As the pressure increases, the conduction and valence band shift to lower and higher energies, respectively. These results indicated that lattice constants and band gap decrease with the increase of pressure.

Vacancy Engineering in 2D Transition Metal Chalcogenide Photocatalyst: Structure Modulation, Function and Synergy Application.

Transition metal chalcogenides (TMCs) are widely used in photocatalytic fields such as hydrogen evolution, nitrogen fixation, and pollutant degradation due to their suitable bandgaps, tunable electronic and optical properties, and strong reducing ability. The unique 2D malleability structure provides a pre-designed platform for customizable structures. The introduction of vacancy engineering makes up for the shortcomings of photocorrosion and limited light response and provides the greatest support for TMCs in terms of kinetics and thermodynamics in photocatalysis. This work reviews the effect of vacancy engineering on photocatalytic performance based on 2D semiconductor TMCs. The characteristics of vacancy introduction strategies are summarized, and the development of photocatalysis of vacancy engineering TMCs materials in energy conversion, degradation, and biological applications is reviewed. The contribution of vacancies in the optical range and charge transfer kinetics is also discussed from the perspective of structure manipulation. Vacancy engineering not only controls and optimizes the structure of the TMCs, but also improves the optical properties, charge transfer, and surface properties. The synergies between TMCs vacancy engineering and atomic doping, other vacancies, and heterojunction composite techniques are discussed in detail, followed by a summary of current trends and potential for expansion.

Deciphering the Performance Enhancement, Cell Failure Mechanism, and Amelioration Strategy of Sodium Storage in Metal Chalcogenides-Based Andes.

Transition metal chalcogenides (TMCs) emerge as promising anode materials for sodium-ion batteries (SIBs), heralding a new era of energy storage solutions. Despite their potential, the mechanisms underlying their performance enhancement and susceptibility to failure in ether-based electrolytes remain elusive. This study delves into these aspects, employing CoS2 electrodes as a case in point to elucidate the phenomena. The investigation reveals that CoS2 undergoes a unique irreversible and progressive solid-liquid-solid phase transition from its native state to sodium polysulfides (NaPSs), and ultimately to a Cu1.8S/Co composite, accompanied by a gradual morphological transformation from microspheres to a stable 3D porous architecture. This reconstructed 3D porous structure is pivotal for its exceptional Na+ diffusion kinetics and resilience to cycling-induced stress, being the main reason for ultrastable cycling and ultrahigh rate capability. Nonetheless, the CoS2 electrode suffers from an inevitable cycle life termination due to the microshort-circuit induced by Na metal corrosion and separator degradation. Through a comparative analysis of various TMCs, a predictive framework linking electrode longevity is established to electrode potential and Gibbs free energy. Finally, the cell failure issue is significantly mitigated at a material level (graphene encapsulation) and cell level (polypropylene membrane incorporation) by alleviating the NaPSs shuttling and microshort-circuit.

Atomic Force Microscopy beyond Topography: Chemical Sensing of 2D Material Surfaces through Adhesion Measurements.

Developing new functionalities of two-dimensional materials (2Dms) can be achieved by their chemical modification with a broad spectrum of molecules. This functionalization is commonly studied by using spectroscopies such as Raman, IR, or XPS, but the detection limit is a common problem. In addition, these methods lack detailed spatial resolution and cannot provide information about the homogeneity of the coating. Atomic force microscopy (AFM), on the other hand, allows the study of 2Dms on the nanoscale with excellent lateral resolution. AFM has been extensively used for topographic analysis; however, it is also a powerful tool for evaluating other properties far beyond topography such as mechanical ones. Therefore, herein, we show how AFM adhesion mapping of transition metal chalcogenide 2Dms (i.e., MnPS3 and MoS2) permits a close inspection of the surface chemical properties. Moreover, the analysis of adhesion as relative values allows a simple and robust strategy to distinguish between bare and functionalized layers and significantly improves the reproducibility between measurements. Remarkably, it is also confirmed by statistical analysis that adhesion values do not depend on the thickness of the layers, proving that they are related only to the most superficial part of the materials. In addition, we have implemented an unsupervised classification method using k-means clustering, an artificial intelligence-based algorithm, to automatically classify samples based on adhesion values. These results demonstrate the potential of simple adhesion AFM measurements to inspect the chemical nature of 2Dms and may have implications for the broad scientific community working in the field.