2D SnS2 Research Articles

Enhanced photocatalytic degradation of organic pollutants by randomly oriented 2D SnS2 nanostructures

Abstract In this study, we present a bottom-up solvothermal technique using tin tetrachloride pentahydrate (SnCl4.5H2O) and thioacetamide as precursors to synthesize SnS2 nanostructures. Different solvents including isopropyl alcohol, ethanol (EN), and ethylene glycol were used in the reaction to enhance the photodegradation efficiency of organic pollutants, Methylene Blue (MB), and Tetracycline (TC) in an aqueous medium under simulated solar light irradiation. The SnS2 nanostructures synthesized with these solvents were characterized using various structural, morphological, and optical techniques, including x-ray diffraction, RAMAN, field emission scanning electron microscope, x-ray photoelectron spectroscopy, UV–Vis, and Brunauer–Emmett–Teller analysis. The choice of solvent was found to significantly affect the structural, morphological, and optical properties of the SnS2 nanostructures. Notably, the sample synthesized with EN as the solvent displayed a unique morphology, enhanced light-harvesting ability, efficient charge carrier separation, and a larger specific surface area, all of which contributed to its superior photocatalytic activity. This sample achieved 99.9% degradation of MB and 95% degradation of TC within 20 and 40 min, respectively. The kinetic analysis revealed maximum rate constant (k) values of 0.15242 min−1 for MB and 0.060 95 min−1 for TC, as determined by the pseudo-first-order kinetic model. We also discuss the plausible mechanism involving visible light-induced electron–hole pairs that generate reactive species, leading to the mineralization of dyes into H2O, CO2, and other gaseous products. The synthesized SnS2 nanostructures demonstrate significant potential for enhanced photocatalytic activity in organic pollutant degradation, underscoring their promise in addressing water pollution challenges.

Mimicking somatic behavior of neurons using the integrate and fire model of 2D SnS memristive switching characteristics

This Letter presents the fabrication and characterization of a 2D SnS memristor, proposing its integrate and fire (I&F) model as a potential hardware implementation of neuronal somatic behavior. The memristor comprises a thin layer of tin (II) sulfide (SnS) sandwiched between copper (Cu) electrodes on a silicon (Si) substrate. This structure exhibits an impressive Roff:Ron ratio of 103 at a read voltage Vrd of 0.25 V with exceptionally low switching Vsw and set Vset voltages of 0.3 and 0.35 V, respectively, with ∼3 order variation between the maximum Rmax and Rmin resistances offered during single voltage sweep cycle. We have explained the memristive behavior using the dual ionic conduction mechanism in the SnS active layer. We extracted the real-time band diagram of SnS using ultraviolet photoelectron spectroscopy, explaining the low Vsw observed. We propose that the emulation of the I&F artificial neuron model exhibited by the fabricated device could serve as a promising application in the field of artificial neuron spiking.

In Situ Construction of SnS2@SnO2 Heterostructure for Photo-Assisted Electrocatalysis of Oxygen Evolution Reaction.

Photo-assisted electrocatalysis has arisen as a promising approach for hydrogen generation by incorporating photocatalysts into electrocatalysts. 2D SnS2 is a photocatalyst that absorbs visible light. However, the rapid recombination of photo-generated electron-hole pairs significantly reduces the overall photocatalytic efficiency of SnS2, limiting its practical application. Thus, this study prepares an in situ heterojunction SnS2@SnO2 using a one-step hydrothermal method. The degradation efficiency of methyl orange (MO) using SnS2@SnO2 is measured, achieving a degradation rate of 92.75% within 1h, which is 1.9 times higher than that of pure SnS2. Additionally, FeNiS/SnS2@SnO2 is synthesized and exhibited significant improvements in the photo-assisted oxygen evolution reaction (OER). It achieves an overpotential of 260mV and a Tafel slope of 65.1mVdec-1 at 10mAcm-2, showing reductions of 11.8% and 31.8%, respectively, compared to FeNiS alone. These enhancements highlight the strong photo-response capability of SnS2@SnO2. Under the internal electric field of SnS2@SnO2, the photogenerated electrons in the conduction band of SnS2 quickly move toward SnO2, facilitating efficient photocatalytic reactions. FeNiS, with a lower Fermi energy level (EF), facilitates electron transfer from SnS2@SnO2 and enhances OER performance by efficiently participating in the reaction. This study paves a new path for 2D photocatalyst materials.

Anisotropic Third Harmonic Generation in 2D Tin Sulfide

AbstractThe in‐plane anisotropic properties of 2D group IV monochalcogenides offer an additional degree of freedom which can be advantageous in optoelectronic applications. Here, it is demonstrated that the third harmonic generation (THG) produced by ultrathin tin (II) sulfide (SnS) is in‐plane anisotropic with respect to the direction of the excitation linear polarization. The polarization‐resolved THG (P‐THG) measurements are described with a nonlinear optics model, which accounts for the orthorhombic crystal structure of the 2D SnS. The relative magnitudes of the χ(3) tensor components are calculated by recording and simultaneously fitting two orthogonal polarization components of the P‐THG signals. Furthermore, the “THG anisotropy ratio” is introduced, which compares the THG intensity produced when the excitation linear polarization is along the armchair crystallographic direction, with the case when it is along the zigzag direction. The experimental findings provide quantitative information on the anisotropic nature of the THG process in various SnS flakes. Nonlinear anisotropic 2D materials can be used in future optoelectronic devices, where anisotropic polarization sensitivity is required. Having an optical tool that quantitatively probes the effect of the in‐plane anisotropy among different 2D materials, could be of considerable importance for evaluating the performance of such materials and devices.

Wide-Bandgap 2D SnS2-Based All-Optical Photonic Devices with Strong Nonlinear Optical Response due to Spatial Self-Phase Modulation

Wide-Bandgap 2D SnS₂-Based All-Optical Photonic Devices with Strong Nonlinear Optical Response due to Spatial Self-Phase Modulation

Spatially selective p-type doping for constructing lateral WS2 p-n homojunction via low-energy nitrogen ion implantation

The construction of lateral p-n junctions is very important and challenging in two-dimensional (2D) semiconductor manufacturing process. Previous researches have demonstrated that vertical p-n junction can be prepared simply by vertical stacking of 2D materials. However, interface pollution and large area scalability are challenges that are difficult to overcome with vertical stacking technology. Constructing 2D lateral p-n homojunction is an effective strategy to address these issues. Spatially selective p-type doping of 2D semiconductors is expected to construct lateral p-n homojunction. In this work, we have developed a low-energy ion implantation system that reduces the implanted energy to 300 eV. Low-energy implantation can form a shallow implantation depth, which is more suitable for modulating the electrical and optical properties of 2D materials. Hence, we utilize low-energy ion implantation to directly dope nitrogen ions into few-layer WS2 and successfully realize a precise regulation for WS2 with its conductivity type transforming from n-type to bipolar or even p-type conduction. Furthermore, the universality of this method is demonstrated by extending it to other 2D semiconductors, including WSe2, SnS2 and MoS2. Based on this method, a lateral WS2 p-n homojunction is fabricated, which exhibits significant rectification characteristics. A photodetector based on p-n junction with photovoltaic effect is also prepared, and the open circuit voltage can reach to 0.39 V. This work provides an effective way for controllable doping of 2D semiconductors.

Two-Dimensional SnS Mediates NiFe-LDH-Layered Electrocatalyst toward Boosting OER Activity for Water Splitting.

NiFe-layered double hydroxides (NiFe-LDHs), as promising electrocatalysts, have received significant research attention for hydrogen and oxygen generation through water splitting. However, the slow oxidation kinetics of NiFe-LDH, due to the limited number of active sites and the low conductivity, hinders the improvement of the water-splitting efficiency. Therefore, to overcome the obstacles, two-dimensional (2D) SnS was first explored to tailor the prepared NiFe-LDH via the hydrothermal method. A NiFe-LDH/SnS heterojunction is built, which is observed from the microstructural investigations. SnS incorporation could greatly improve the conductivity of the NiFe-LDH sheets, which was reflected by the reduced charge transfer resistance. Moreover, SnS layers modulated the electronic environment around the active sites, favoring the adsorption of intermediates during the oxygen evolution reaction (OER) process, which was verified by density functional theory calculations. A synergistic effect induced by the NiFe-LDH/SnS heterostructure promoted the OER activities in electrical, electronic, and energetic aspects. Consequently, the as-prepared NiFe-LDH/SnS electrocatalyst greatly improved the electrocatalytic performance, exhibiting 20% and 27% reductions in the overpotential and Tafel slope compared with those of pristine NiFe-LDH, respectively. The results provide a strategy for regulating NiFe-based electrocatalysts by using emerging 2D materials to enhance water-splitting efficiency.

Nanomaterial SnS2-Based Sensor for VOC Gas Detection at Room Temperature

Real-time indoor hazardous gases monitoring has gained interest in ensuring human health. An effort to design gas sensing devices, which are compact in size, flexible, and low power consumption, providing high-performance sensing plays a crucial role in precise sensing of the indoor environment. Here, we have fabricated 2D SnS2 flakes for gas sensor. The 2D ultra-thin SnS2, including a few layers, shows fascinating sensing toward Volatile organic compounds (VOCs) under room temperature with high response and fast reaction speed. The short-term stability versus time of the SnS2 sensor is investigated. Due to the great adsorption of gaseous molecules, the SnS2-gas sensor operates at room temperature without external heating sources. The Schottky junction-based sensor is one of the key factors contributing to the higher performance of the sensor. Furthermore, its VOC-sensing mechanism is explained obviously through the energy band diagram. The SnS2-layer is considered a promising candidate in indoor VOCs monitoring and respiratory biomarker analysis in the future.

Fabrication of 2D SnS2 nanoflake photoanodes by a two-step process

Fabrication of 2D SnS2 nanoflake photoanodes by a two-step process

Gas Sensing Properties of PLD Grown 2D SnS Film: Effect of Film Thickness, Metal Nanoparticle Decoration, and In Situ KPFM Investigation.

This study employs novel growth methodologies and surface sensitization with metal nanoparticles to enhance and manipulate gas sensing behavior of two-dimensional (2D)SnS film. Growth of SnS films is optimized by varying substrate temperature and laser pulses during pulsed laser deposition (PLD). Thereafter, palladium (Pd), gold (Au), and silver (Ag) nanoparticles are decorated on as-grown film using gas-phase synthesis techniques. X-ray diffraction (XRD), Raman spectroscopy, and Field-emission scanning electron microscopy (FESEM) elucidate the growth evolution of SnS and the effect of nanoparticle decoration. X-ray photoelectron spectroscopy (XPS) analyses the chemical state and composition. Pristine SnS, Ag, and Au decorated SnS films are sensitive and selective toward NO2 at room temperature (RT). Ag nanoparticle increases the response of pristine SnS from 48 to 138% toward 2ppm NO2, which indicates electronic and chemical sensitization effect of Ag. Pd decoration on SnS tunes its selectivity toward H2 gas with a response of 55% toward 70ppm H2 and limit of detection (LOD) < 1ppm. In situ Kelvin probe force microscopy (KPFM) maps the work function changes, revealing catalytic effect of Ag toward NO2 in Ag-decorated SnS and direct charge transfer between Pd and SnS during H2 exposure in Pd-decorated SnS.

In situ construction of a 2D/2D SnS2/MXene heterojunction for visible-light photocatalytic uranium reduction

A 2D MXene loaded on 2D SnS2 was successfully synthesized, which exhibits improved uranium reduction by forming a built-in electric field.

First principles study of high-performance sub-5-nm monolayer SnS field-effect transistors

&lt;sec&gt;Currently, Si-based field-effect transistors (FET) are approaching their physical limit and challenging Moore's law due to their short-channel effect, and further reducing their gate length to the sub-10 nm is extremely difficult. Two-dimensional (2D) layered semiconductors with atom-scale uniform thickness and no dangling bonds on the interface are considered potential channel materials to support further miniaturization and integrated electronics. Wu et al. [Wu F, et al. &lt;ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.nature.com/articles/s41586-021-04323-3"&gt;2022 &lt;i&gt;Nature&lt;/i&gt; &lt;b&gt;603&lt;/b&gt; 259&lt;/ext-link&gt;] successfully fabricated an FET with gate length less than 1 nm by using atomically thin molybdenum disulfide with excellent device performance. This breakthrough has greatly encouraged further theoretical predictions regarding the performance of 2D devices. Additionally, 2D SnS has high carrier mobility, anisotropic electronic properties, and is stable under ambient condition, which is conducive to advanced applications in 2D semiconductor technology. Herein, we explore the quantum transport properties of sub-5 nm monolayer (ML) SnS FET by using first-principles quantum transport simulation. Considering the anisotropic electronic SnS, the double-gated-two-probe device model is constructed along the armchair direction and the zigzag direction of ML SnS. After testing five kinds of doping concentrations, a doping concentration of 5×10&lt;sup&gt;13&lt;/sup&gt; cm&lt;sup&gt;–2&lt;/sup&gt; is the best one for SnS FET. We also use the underlaps (ULs) with lengths of 0, 2, and 4 nm to improve the device performance. On-state current (&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt;) is an important parameter for evaluating the transition speed of a logic device. A higher &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt; of a device can help to increase the switching speed of high-performance (HP) servers. The main conclusions are drawn as follows.&lt;/sec&gt;&lt;sec&gt;1) &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt; values of the n-type 2 nm (UL = 4 armchair), 3 nm (UL = 2), 4 nm (UL = 3), 5 nm (UL = 0) and the p-type 1 nm (UL = 2 zigzag), 2 nm (UL = 2 zigzag), 3 nm (UL = 2, 4 zigzag), 4 nm (UL = 2, 4 zigzag), and 5 nm (UL = 0, armchair/zigzag) gate-length devices can meet the standards for HP applications in the next decade in the International Technology Roadmap for semiconductors (ITRS, 2013 version).&lt;/sec&gt;&lt;sec&gt;2) &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt; values of the n-type device along the armchair direction (31–2369 μA/μm) are larger than those in the zigzag direction (4.04–1943 μA/μm), while &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt; values of the p-type along the zigzag direction (545–4119 μA/μm) are larger than those in the armchair direction (0.7–924 μA/μm). Therefore, the p-type ML GeSe MOSFETs have a predominantly anisotropic current.&lt;/sec&gt;&lt;sec&gt;3) &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt; value of the p-type 3 nm gate-length (UL = 0) device along the zigzag direction has the highest value 4119 μA/μm, which is 2.93 times larger than that in the same gate-length UL = 2 (1407 μA/μm). Hence, an overlong UL will weaken the performance of the device because the gate of the device cannot well control the UL region. Thus, a suitable length of UL for FET is very important.&lt;/sec&gt;&lt;sec&gt;4) Remarkably, &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;on&lt;/sub&gt; values of the p-type devices (zigzag), even with a gate-length of 1 nm, can meet the requirements of HP applications in the ITRS for the next decade, with a value as high as 1934 μA/μm. To our knowledge, this is the best-performing device material reported at a gate length of 1 nm.&lt;/sec&gt;&lt;sec&gt;5) Subthreshold swing (SS) evaluates the control ability of the gate in the subthreshold region. The better the gate control, the smaller the SS of the device is. The limit of SS for traditional FET is 60 mV/dec (at room temperature). Values of SS for ML SnS FET alone zigzag direction are less than those along the armchair direction because the leakage current is influenced by the effective mass.&lt;/sec&gt;

Oxidation-enabled SnS conversion to two-dimensional porous SnO2 flakes towards NO2 gas sensing.

Tin dioxide (SnO2)-based electronic materials and gas sensors have attracted extensive attention from academia and industry. Herein we report the preparation of two-dimensional (2D) porous SnO2 flakes by thermal oxidation of 2D SnS flakes that serve as a self-sacrificial template. An oxidation-enabled, temperature-dependent matter conversion from SnS through three-phase SnS-SnS2-SnO2 (400 °C) and two-phase SnS2-SnO2 (600 °C) to pure-phase SnO2 (≥800 °C) is disclosed by means of combined XRD, TG-DSC and XPS studies. Meanwhile, the associated chemical reactions and the mass and heat changes during this solid-state conversion process are clarified. The as-prepared 2D SnO2 flakes exhibit structural porosity with tunable pore sizes and crystallite sizes/crystallinity, resulting in superior potential for NO2 sensing. At the optimized operating temperature of 200 °C, the prototype gas sensors made of porous SnO2 flakes show competitive sensing parameters in a broad NO2 concentration range of 50 ppb-10 ppm in terms of high response, faster response/recovery speeds, and good selectivity and stability. A sensing mechanism involving the adsorption and desorption of NO2/O2 molecules and the possible surface reactions is further rationalized for the SnO2 NO2 gas sensors.

Active Diatomic Pairs Induced Interlayer Spacing Engineering in 2D Materials for Highly Efficient Energy Conversion Device

Ammonia, the second largest commercialized synthetic chemical in the world, is widely used for fertilizer and all nitrogen-atom-containing chemicals production. Energy conversion devices by electrochemical nitrate reduction reaction (eNO3RR) offer a green and appealing approach for sustainable ammonia synthesis but hindering by the multi-step chemical reaction and competitive hydrogen generation. To this end, exploring efficient nitrate-to-ammonia conversion devices play a critical role in developing ammonia electrosynthesis. Two-dimensional (2D) materials, like MoS2 and SnS2, have been considered promising energy electrocatalytic materials owing to the advantages of large specific areas that not only provide much more active sites but act as appropriate support to combine other materials. Recently, interlayer engineering on 2D materials has attracted intense interest from scientists because it could tune the chemical affinity of absorbates, which determines the energy barriers during multi-step electrocatalysis device. Therefore, it is valuable to investigate the effect of interlayer spacing in 2D materials on eNO3RR. Active diatomic A-B pairs, such as diatomic Pt-Ce and Pd-Ce pairs, have strong interactions that can be introduced into 2D materials to trigger the interlayer spacing change. For example, the lanthanide series rare earth element (Ce) can be a potential candidate to achieve interlayer expansion since it has a relatively higher atomic radius than most of the atoms, while intercalating Pt or Pd can close the interlayer spacing through solid interaction. In this work, by introducing active diatomic Pt-Ce and Pd-Ce pairs into SnS nanosheets through doping and intercalating, the interlayer spacing of 2D SnS nanosheets achieves both expansion (~6.5 %) and compression (~8.0%). More importantly, the samples with various interlayer spacing show distinguishing nitrate reduction efficiency. The SnS nanosheet with compressed interlayer spacing can reach high ammonia Faradaic efficiencies (surpassing 90%) and yield rate (~0.31 mmol cm− 2 h− 1). Different characterize tools are applied to investigate the mechanism, including in-situ Raman spectra and DFT calculations. The results attribute to the variational delocalized electron density of localized p-orbital in Sn, which contribute to the faster conversion of the rate-determining step (*NO3→*NO2) and the higher chemical affinity of NO3 - and NO2 - in eNO3RR, and the suppressed hydrogen evolution reaction in the meantime. Taken together, our work verifies the feasibility of tailoring the interlayer spacing of 2D materials by active diatomic pairs and further implicates interlayer engineering in promoting efficient electrochemical nitrate conversion devices.

Integrated In-Memory Sensor and Computing of Artificial Vision Based on Full-vdW Optoelectronic Ferroelectric Field-Effect Transistor.

The development and application of artificial intelligence have led to the exploitation of low-power and compact intelligent information-processing systems integrated with sensing, memory, and neuromorphic computing functions. The 2D van der Waals (vdW) materials with abundant reservoirs for arbitrary stacking based on functions and enabling continued device downscaling offer an attractive alternative for continuously promoting artificial intelligence. In this study, full 2D SnS2 /h-BN/CuInP2 S6 (CIPS)-based ferroelectric field-effect transistors (Fe-FETs) and utilized light-induced ferroelectric polarization reversal to achieve excellent memory properties and multi-functional sensing-memory-computing vision simulations are designed. The device exhibits a high on/off current ratio of over 105 , long retention time (>104 s), stable cyclic endurance (>350 cycles), and 128 multilevel current states (7-bit). In addition, fundamental synaptic plasticity characteristics are emulated including paired-pulse facilitation (PPF), short-term plasticity (STP), long-term plasticity (LTP), long-term potentiation, and long-term depression. A ferroelectric optoelectronic reservoir computing system for the Modified National Institute of Standards and Technology (MNIST) handwritten digital recognition achieved a high accuracy of 93.62%. Furthermore, retina-like light adaptation and Pavlovian conditioning are successfully mimicked. These results provide a strategy for developing a multilevel memory and novel neuromorphic vision systems with integrated sensing-memory-processing.

Formamide-assisted synthesis of SnS2 nanosheets for high capacity and stable Li-ion battery

Two-dimensional (2D) SnS2 nanosheets attracted particular attention for their ultrahigh theoretical storage capacity in lithium-ion batteries (LIBs). Herein, we have developed a one-pot scalable formamide-assisted method to prepare SnS2 nanosheets. These obtained SnS2 nanosheets are subsequently assembled with MXene to form SnS2/MXene via a vacuum filtration technique. Due to the advantages of abundant active sites, superior electron/ion transfer kinetics and unique 2D interlayer structure with large heterointerface, the SnS2/MXene anode demonstrates a high specific capacity (954.2 mA h g−1 at 0.1 mA g−1), outstanding rate capability (512 mA h g−1 at 5 A g−1), and excellent cycling stability (96.4% capacity retention at 3 A g−1 even over 400 cycles). This work offers a facile and green strategy for the preparation a series of 2D metal sulfides materials which have potential applications in LIBs applications.

Low-Temperature Centimeter-Scale Growth of Layered 2D SnS for Piezoelectric Kirigami Devices.

Tin monosulfide (SnS) is a promising piezoelectric material with an intrinsically layered structure, making it attractive for self-powered wearable and stretchable devices. However, for practical application purposes, it is essential to improve the output and manufacturing compatibility of SnS-based piezoelectric devices by exploring their large-area synthesis principle. In this study, we report the chemical vapor deposition (CVD) growth of centimeter-scale two-dimensional (2D) SnS layers at temperatures as low as 200 °C, allowing compatibility with processing a range of polymeric substrates. The intrinsic piezoelectricity of 2D SnS layers directly grown on polyamides (PIs) was confirmed by piezoelectric force microscopy (PFM) phase maps and force-current corroborative measurements. Furthermore, the structural robustness of the centimeter-scale 2D SnS layers/PIs allowed for engraving complicated kirigami patterns on them. The kirigami-patterned 2D SnS layer devices exhibited intriguing strain-tolerant piezoelectricity, which was employed in detecting human body motions and generating photocurrents irrespective of strain rate variations. These results establish the great promise of 2D SnS layers for practically relevant large-scale device technologies with coupled electrical and mechanical properties.

Constructing a noble-metal-free 0D/2D CdS/SnS2 heterojunction for efficient visible-light-driven photocatalytic pollutant degradation and hydrogen generation

Semiconductor photocatalysis has attracted the attention of a wide audience for its outstanding capabilities in water purification and energy conversion. Herein, a noble-metal-free nanoheterojunction is created by planting zero-dimensional (0D) CdS nanograins, of 10–20 nm in size, on the surface of 2D SnS2 nanosheets (NSs) using an in situ chemical bathing deposition process, where SnS2 NSs have an average diameter of 400 nm and thicknesses of less than 20 nm. The possible formation mechanism of the CdS/SnS2 (CS/SS) heterogeneous nanostructure is elaborated upon. The catalytic activities over CS/SS nanocomposites for the photodegradation of organic dye and hydrogen evolution from photolysis water splitting are examined under visible light irradiation. The apparent rate constant (k) of the optimal CS/SS-3 composite in the decontamination of methylene blue (MB) is up to 3.34 and 1.87 times as high as that of pristine SnS2 and pure CdS counterparts, respectively. The optimized CS/SS-3 sample consistently achieves the highest photocatalytic hydrogen production rate, at 10.3 and 5.7 folds higher than that of solo SnS2 and CdS panels, respectively. The boosted photocatalytic capacities of CdS/SnS2 heterostructures are essentially attributed to the formation of the closely interfacial incorporation of CdS and SnS2 semiconductors, resulting in the effective charge transportation and spatial separation of the photoinduced electron–hole pairs. Furthermore, the traditional type-II charge transfer pathway is proposed based on the perfect band structure and the free radical experiment results.

Thermal conductivity of van der Waals heterostructure of 2D GeS and SnS based on machine learning interatomic potential

van der Waals heterostructures have provided an unprecedented platform to tune many physical properties for two-dimensional materials. In this work, thermal transport properties of van der Waals heterostructures formed by vertical stacking of monolayers GeS and SnS have been investigated systematically based on machine learning interatomic potential. The effect of van der Waals interface on the lattice thermal transport of 2D SnS and GeS can be well clarified by introducing various stacking configurations. Our results indicate that the van der Waals interface can strongly suppress the thermal transport capacity for the considered heterostructures, and either the average thermal conductivity per layer or the 2D thermal sheet conductance for the considered heterostructures is lower than that of corresponding monolayers. The suppressed thermal conductivity with tunable in-plane anisotropy in SnS/GeS heterostructures can be ascribed to the enhanced interface anharmonic scattering, and thus exhibits obvious interface-dependent characteristics. Therefore, this work highlights that the van der Waals interface can be employed to effectively modulate thermal transport for the 2D puckered group-IV monochalcogenides, and the suppressed lattice thermal conductivity together with interface-dependent phonon transport properties in the SnS/GeS heterostructure imply the great potential for corresponding thermoelectrical applications.

2D Layered Material Interface Confined Dynamically in-Situ Generated Ni(OH)2 Triggers Ultrafast Oxygen Evolution

Basic insights into the structural evolution of oxygen electrocatalysts under operating conditions are of substantial importance for designing water oxidation catalysts. Recently, the development of potent oxygen evolution reaction (OER) electrocatalysts has trigger researcher’s attention. Conversely, the design of active and stable catalyst under alkaline media is a substantial issues and challenges of the area due to the poor cyclability of catalysts and the sluggish water dissociation kinetics. Our work reports the design and synthesis of a two-dimensional (2D) SnS2 confined in-situ generated Ni(OH)2 nanoparticle electrocatalyst, which accelerates water oxidation and exhibits long term durability in alkaline solutions, leading to significant improvement in OER performance. A two-step method was used to synthesize the electrocatalyst, starting with the lithium intercalation of exfoliated SnS2 nanosheets followed by Ni2+ exchange in alkaline media to form SnS2 intercalated with Ni(OH)2 nanoparticles (denoted Ni-Ex-SnS2), which was fully characterized by in-situ X-ray absorption spectroscopy for two cycles. Electrochemical tests indicated that the electrocatalyst exhibits superior OER activity and excellent stability, with an onset overpotential and Tafel slope as low as 17 mV and 42 mV dec−1, respectively, which are among the best values reported in alkaline media. Furthermore, density functional theory calculations show that the co-joint roles of Ni(OH)2 nanoparticles and SnS2 nanosheets result in the excellent activity of the Ni-Ex-SnS2 electrocatalyst, and the good stability is attributed to the confinement of the in-situ generated Ni(OH)2 nanoparticles. The combination of electrochemical measurement, operando X-ray absorption spectroscopy and density functional theory (DFT) calculations revealed that the in-situ generated and confined Ni(OH)2 as the critical active species via the principle of nano-confinment and in-situ generations. This work proposes the plausible catalytic reaction pathway and mechanism.