Two-dimensional SnS2 Research Articles

Bottom-Up Confined Synthesis of Air-Stable Two-Dimensional SnS and SnS2 between Hexagonal Boron Nitride Nanosheets

Bottom-Up Confined Synthesis of Air-Stable Two-Dimensional SnS and SnS₂ between Hexagonal Boron Nitride Nanosheets

Effect of hydrogen sulfide concentration on two-dimensional SnS2 film by atomic layer deposition in annealing process

Two-dimensional materials are widely studied due to its unique physical, optical, electrical properties, and good compatibility with various synthesis methods. And among the many fabrication methods, tin disulfide (SnS2) material, a two-dimensional (2D) material that can be achieved with accurate thickness control using atomic layer deposition (ALD), high uniformity and conformality even at low process temperatures is attracting attention. However, since the crystallinity of the thin film is low at a low process temperature, various post-annealing methods are being studied to compensate for film quality. In this work, we compared the crystal structures, chemical binding energies, and electrical properties of the thin films by post-annealing SnS2thin films according to the hydrogen sulfide concentrations of 4.00% and 99.99% in the hydrogen sulfide atmospheres. The crystallinity, grain size, and carrier concentrations of the SnS2thin film were the highest at a post-annealing temperature of 350 °C at a hydrogen sulfide concentration of 99.99%, and the chemical binding energies also corresponded with the standard Sn4+states, forming a pure 2D-hexagonal SnS2phase. In addition, SnS2thin films deposited via ALD showed high uniformity and conformality in large-scale wafers and trench structure wafers.

Boosting efficiency in dual-absorber RbPbBr3 perovskite solar cell: the role of two-dimensional GeS and SnS2 as electron transport layers

This paper presents a comprehensive investigation into the electrical characteristics of a perovskite solar cell. The n-i-p cell is based on a low band gap rubidium–lead-bromide (RbPbBr3) perovskite with an energy level of 1.31 eV. The study also evaluates the impact of high mobility two-dimensional GeS and SnS2 as electron transport layers (ETLs) on the cell’s performance. These ETLs have a wide band gap and provide a hole blocking layer due to their high valence band-offset. Additionally, a thin film MoTe2 with a band gap of 1 eV is considered as a complementary absorber for capturing near-infrared solar spectrum. The investigation focuses on the influence of critical physical and structural design parameters on the electrical parameters of the cell. The optimized device with SnS2 as the ETL exhibits a power conversion efficiency (PCE) of 25.03%, an open circuit voltage of 0.95 V, a short circuit current density of 33 mA cm−2, and a fill factor of 80.31%. Similarly, the device with GeS as the ETL achieves a PCE of 25.14%, an open circuit voltage of 0.96 V, a short circuit current density of 33.01 mA cm−2, and a fill factor of 80.66%. Furthermore, a statistical analysis is conducted by calculating the coefficient of variation to assess the sensitivity of the cell’s electrical measures to the variation of design parameters and operating temperature. The results highlight that defects in the absorber layer, work function of the back contact, and ambient temperature are critical design parameters that can significantly impact the device performance. Overall, the utilization of high mobility wide band gap ETLs, in combination with the low band gap perovskite, offers a promising approach for the design of high-performance solar cells.

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.

Preparation of vertical structure SnS2/SnSe2/H–TiO2 ternary heterojunction and its high performance ultraviolet/visible photodetector

Developing highly efficient heterojunction photodetector, especially ternary heterojunctions of vertical structure, is a promising strategy to enhance the migration of photo-generated electron for exploit potentialities of optoelectronic devices. In this study, we successfully deposited two-dimensional layered SnSe2 NSs and SnS2 NSs vertically on TiO2 NTs arrays using chemical vapor deposition (CVD), constructing a novel ternary SnS2/SnSe2/H–TiO2 heterojunction. The morphology, structure, and composition of the samples were analyzed, and highly sensitive ultraviolet/visible light photodetectors were fabricated. Photocurrent measurements demonstrated that the prepared SnS2/SnSe2/H–TiO2 ternary heterojunction exhibited superior light detection capability at different wavelengths (370 nm, 450 nm, 520 nm) compared to the pristine H–TiO2 and its binary heterojunctions (SnS2/H–TiO2, SnSe2/H–TiO2). Under a bias voltage of 1 V and 370 nm illumination, it achieved a high photocurrent of 7.45 mA cm−2, a switch ratio of 7.924, as well as high responsivity (9.39 A/W), high EQE (3.15 × 103 %), and large detectivity (9.53 × 1010 Jones). The excellent performance of the SnS2/SnSe2/H–TiO2 ternary heterojunction reveals its enormous potential in the development of wide-band, high-performance photodetectors.

Photogating enhanced photodetectors dominated by rubrene nanodots modified SnS2 films

The hybrid-induced photogating effect is considered as an effective way for photoconductance modulating in low-dimensional photodetectors. Besides, through constructing the local photogate vertical heterostructures on two-dimensional SnS2 surface can significantly increase its photoconductive gain. However, the potential of this photogain mechanism for SnS2 films has not yet been revealed in practical photodetection devices. To investigate its special advantages on promoting the optical-sensing activity, the high-quality SnS2 films with discrete, micro-area, and uniform rubrene-nanodots modification have been prepared. Benefit from the local interfacial photogating effect induced by hole trap states by rubrene-nanodots, the light-absorption and carrier-excitation efficiencies were significantly enhanced. Afterwards, the high-performance photodetector was designed based on the photogate vertical heterostructures of rubrene-nanodots/SnS2, which demonstrated an enhanced photoelectric response to 1064 nm light. Note that the maximum photocurrent density, photoresponsivity, and photodetectivity can reach up to 0.389 mA cm−2, 388.71 mA W−1, and 1.13 × 1010 Jones, respectively. Importantly, the optimal band-structure offsets accelerated the localized hole transfer from SnS2 film to rubrene-nanodots. The trapped holes in rubrene-nanodots induced an enhanced interface gating effect, which may help to modulate the number and lifetime of excess electrons under light illuminations. These superior features make the newly-developed photodetector be suitable for future multifunctional photodetection applications.

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.

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.

Enhanced photocatalytic reduction of CO2 using a novel 2D/0D SnS2/CeO2 binary photocatalyst with Z-scheme heterojunction and oxygen vacancy

In this work, suitable band gap width, strong photo-response to visible light, and a high photogenerated carrier density offered by an important member of layered sulfides, SnS2, were kept in view for designing and producing a highly effective photocatalyst for CO2 reduction. Hence, SnS2/CeO2 heterojunction composite photocatalysts were triumphally fabricated by a facile in situ hydrothermal synthesis method, combining advantages of the built-in electric field and oxygen vacancies of two materials. Various characterization techniques were exploited to scrutinize the photocatalyst’s structure and confirm that the carrier transport efficiency and photocatalytic performance are enhanced by the synergistic impact of the heterojunction structure and presence of oxygen vacancies. Owing to the successful loading of zero-dimensional CeO2 nanoparticles onto two-dimensional SnS2 nanosheets, the 2D/0D structure improves the photo-response range of the composites and provides faster electron transfer rates. The composite material maintained the hydrophobic characteristic of single SnS2, while inhibiting the hydrophilic property of single CeO2. As a result, CO and CH4 yields of prepared binary Z-type heterojunction photocatalysts are 24.6 and 4.4 folds higher than those of single SnS2, respectively. This innovative study will contribute to exploration of SnS2-based photocatalytic materials and provide a new feasible direction for light energy-driven CO2 reduction.

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.

Two-Dimensional SnS and SnSe as Hosts of K-Ion Storage: A First-Principles Prediction

Two-Dimensional SnS and SnSe as Hosts of K-Ion Storage: A First-Principles Prediction

Etching anisotropy in two-dimensional SnS layered crystals using a thiol-amine solvent mixture as an etchant

Etching anisotropy in two-dimensional SnS layered crystals using a thiol-amine solvent mixture as an etchant

Hierarchical ZnS-SnS2 @C nanocomposite as superior-rate and long-life anode for sodium ion batteries

Two-dimensional SnS2 are known as potential anodes for Na-ion batteries owing to high energy density and low voltage plateau. However, SnS2 suffers from structural instability, material fragmentation, and low electrical conductivity. We propose to design a hierarchical structure in which the outer layer is conductive carbon, the middle layer is SnS2, and the inner layer is ZnS. Such a design can effectively solve the problem of SnS2: the conductive carbon can improve the conductivity of the composite, and the ZnS in the inner layer stabilizes the structure. ZnS-SnS2 @C has superior rate performance (257.7 mAh g−1 at 5 A g−1) and cycle durability (234.4 mAh g−1 after 500 cycles with the capacity retention rate of 61.33%). In situ EIS reveals that ZnS-SnS2 @C has lower charge transfer resistance during cycling. Theoretical calculations also confirmed that the diffusion energy barrier of Na ions in ZnS-SnS2 @C is lower than that of ZnS and SnS2. The synergistic effect between SnS2 and ZnS and carbon coating with well-designed hierarchical structure provides an effective strategy to improve Na intercalation performance for anode materials.

Unlocking performance potential of two-dimensional SnS2 transistors with solution-processed high-k Y:HfO2 film and semimetal bismuth contact

Two-dimensional (2D) tin disulfide (SnS2) is emerging as a viable channel material for high-performance field-effect transistors (FET) with high intrinsic mobility. To implement a high-performance two-dimensional SnS2 FET, high field-effect mobility (μFE), steep subthreshold swing (SS), high on-current value (Ion), and high on/off ratio (Ion/Ioff) must be realized. To improve these parameters, we first fabricated a high-k (∼30.5) yttrium-doped hafnium dioxide (Y:HfO2) film through a solution process to suppress Coulomb electron scattering, and to enhance the semiconductor-dielectric interface with an efficient metal–oxygen framework and a very smooth (root mean square = 0.29 nm) surface. Second, we induced Fermi level depinning by introducing a semimetal bismuth (Bi) contact with a low density of states (DOS) at the Fermi level to suppress the metal-induced gap state (MIGS). Through these two strategies, the SnS2 FET obtained high μFE (60.5 cm2V-1s−1), the SS theoretical limit of 60 mV/dec, negligible Schottky barrier height, high normalized on-current (IonL/W) of 90.6 μA, and high Ion/Ioff of 3 × 107, demonstrating that SnS2 can be re-evaluated as a potentially effective 2D channel material.

Theoretical screening and investigation on electrocatalytic nitrogen fixation of single transition metal atom supported by monolayer SnS2

Dispersing transition metal atoms on substrates is a novel approach to constructing (photo) electrocatalysts, which has received extensive attention in electrocatalytic nitrogen reduction reaction (NRR). Two-dimensional monolayer SnS2 is an easy-to-prepare, low-cost, and low-environmental pollution material. In this work, through first-principles calculation, fifteen transition metal atoms (TM = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Mo, Ru, Hf, Ta, W, Os) supported on monolayer SnS2 (TM@SnS2), respectively, are investigated as an efficient NRR catalyst. The screening of the NRR catalyst is followed by a three-step method and our results indicate that a single W atom supported on top of the Sn atom of SnS2 (W@SnS2) has the best catalytic activity, with an over potential of 0.42 V along the distal pathway, which is much lower than the reported values based on SnS2. Moreover, the N2 adsorption on W@SnS2 is far superior to the hydrogen atom adsorption, which can inhibit the competitive side reaction effectively. Our results are helpful for the design of NRR catalysts based on SnS2 monolayer.

Single atom catalysts in Van der Waals gaps

Single-atom catalysts provide efficiently utilized active sites to improve catalytic activities while improving the stability and enhancing the activities to the level of their bulk metallic counterparts are grand challenges. Herein, we demonstrate a family of single-atom catalysts with different interaction types by confining metal single atoms into the van der Waals gap of two-dimensional SnS2. The relatively weak bonding between the noble metal single atoms and the host endows the single atoms with more intrinsic catalytic activity compared to the ones with strong chemical bonding, while the protection offered by the layered material leads to ultrahigh stability compared to the physically adsorbed single-atom catalysts on the surface. Specifically, the trace Pt-intercalated SnS2 catalyst has superior long-term durability and comparable performance to that of commercial 10 wt% Pt/C catalyst in hydrogen evolution reaction. This work opens an avenue to explore high-performance intercalated single-atom electrocatalysts within various two-dimensional materials.

Ppb-level NO2 sensing properties at room temperature of ultra-thin SnS2 nanopetals annealed at different temperatures

Two-dimensional SnS2 with stable electron transport capacity, high specific surface area, and high surface activity due to defects such as sulfur vacancies, is a suitable candidate for gas sensors at room temperature. Here, ultra-thin SnS2 nanopetals are synthesized and planar type sensors are obtained through coating SnS2 on a substrate with interdigitated electrodes. Samples annealed at different temperatures were characterized and their gas-sensing properties were compared. The sensor annealed at 200 °C in the air of the muffle furnace (SnS2-200) exhibits the best sensing performance with the high response of 24.20 to 100 ppb NO2 at RT and ultra-low detection limit of 5 ppb NO2. Moreover, the SnS2-200 sensor also possesses good repeatability, selectivity and long-term stability. The excellent sensing performances prove that the SnS2 holds excellent application prospects in the detection of trace-level NO2.

Controllable Potassium Iodide-Assisted Preparation of Two-dimensional SnS2 for Hydrogen Evolution Reaction

The controllable preparation of Two-dimensional transition metal chalcogenides (TMDCs) is very important. However, the uncontrollable growth of SnS2 by chemical vapor deposition (CVD) and the unsatisfactory performance of hydrogen evolution reaction (HER) based on SnS2 have hindered its applications. Herein, we reported the direct synthesis of high-quality 1T-SnS2 with various morphologies via potassium iodide-assisted CVD. On the basis of CVD technology, We have developed process technology to grow different shapes of SnS2 from dot line to fishbone controlled by growth conditions. The growth mechanism of SnS2 was studied, and their HER performance with different morphologies of SnS2 was investigated. The growth trend of 2D SnS2 provides a reference for the controllable preparation of TMDCs materials. These results demonstrate that TMDCs can adjust the performance of HER through shape control.

Novel insights into the unique intrinsic sensing essences of 2D tin chalcogenides for ethanol: From hexagonal SnS2 to orthorhombic SnS

Introducing orthorhombic SnS phase into two-dimensional (2D) hexagonal SnS2 crystal to form in-plane heterojunctions has become a promising approach to facilitate the sensitivity of SnS2 towards trace gases. However, its surface sensitization mechanism remains to be exploited in addition to the heterointerface effect. Hence, to dig into it, we explored the surface adsorption of SnS and SnS2 from unique surface electron configurations by combing experimental, computational and bionic approaches. Taking ethanol vapor as the target gas, orthorhombic SnS shows rapid detection of trace ethanol with a sub-ppm level at room temperature (RT). In contrast, hexagonal SnS2 is more suitable for detecting ethanol vapor with much higher concentrations (above 50 ppm). First-principles calculations and porcupine quill models further reveal that unlike the inactive symmetry of electrons on SnS2 surface, the rotational symmetry breaking of the stereochemically-active SnS surface leads to the oriented rearrangement of its surface electrons, which greatly facilitates the adsorption of trace ethanol molecules on SnS. On these basis, we renew the design concept of SnS–SnS2 in-plane heterostructures. This work reveals the structure-property relationship between the crystalline structures and gas-sensitive characteristics of 2D tin chalcogenides from a brand-new perspective, and helps the design and research of novel lateral heterostructures.

First-principles study of magnetic and optical properties in dopant-doped two-dimensional SnS2

We use GGA and GGA + U methods to calculate the magnetic and optical properties of pure, Fe doped, Mn doped, (Fe, Mn) co-doped and (Fe, Mn, VSn) co-doped SnS2 based on first principles. The results show that both Fe doping and Mn doping have spin polarization. The most stable (0, 3) configuration of (Fe, Mn) co-doped SnS2 exhibits magnetism, which mainly comes from the magnetic coupling between Fe-3d state, Mn-3d state and the nearest neighbor S-3p state of doped atoms. The most stable (0, 3, 1) configuration in (Fe, Mn, VSn) co-doped SnS2 also exhibits magnetism, which comes from the magnetic coupling between Fe-3d state, Mn-3d state and the nearest neighbor S-3p state of doped atoms. We also find that the introduction of doping atoms enhances the electromagnetic absorption capacity of the ɛ1(ω) of the dielectric function and increases the electrical conductivity. Mn doped and (Fe, Mn) co-doped SnS2 have low transmittance properties in visible and ultraviolet light ranges, while Fe doped and (Fe, Mn, VSn) co-doped SnS2 have high transmittance properties in visible and ultraviolet light ranges. Our findings indicate that Fe doped, Mn doped, (Fe, Mn) co-doped and (Fe, Mn, VSn) co-doped SnS2 systems have potential applications in spin semiconductors and optoelectronic devices.