Insights into Electrochemical CO2 Reduction on SnS2: Main Product Switch from Hydrogen to Formate by Pulsed Potential Electrolysis

2023-05-29T13:08:16+00:00May 29th, 2023|Categories: Publications|Tags: |

Tin disulfide (SnS2) is a promising candidate for electrosynthesis of CO2-to-formate while the low activity and selectivity remain a great challenge. Herein, we report the potentiostatic and pulsed potential CO2RR performance of SnS2 nanosheets (NSs) with tunable S-vacancy and exposure of Sn-atoms or S-atoms prepared controllably by calcination of SnS2 at different temperatures under the H2/Ar atmosphere. The catalytic activity of S-vacancy SnS2 (Vs-SnS2) is improved 1.8 times, but it exhibits an exclusive hydrogen evolution with about 100% FE under all potentials investigated in the static conditions. The theoretical calculations reveal that the adsorption of *H on the Vs-SnS2 surface is energetically more favorable than the carbonaceous intermediates, resulting in active site coverage that hinders the carbon intermediates from being adsorbed. Fortunately, the main product can be switched from hydrogen to formate by applying pulsed potential electrolysis benefiting from in situ formed partially oxidized SnS2-x with the oxide phase selective to formate and the S-vacancy to hydrogen. This work highlights not only the Vs-SnS2 NSs lead to exclusively H2 formation, but also provides insights into the systematic design of highly selective CO2 reduction catalysts reconstructed by pulsed potential electrolysis.

Published in: "Angewandte Chemie International Edition".

Insights into Electrochemical CO2 Reduction on SnS2: Main Product Switch from Hydrogen to Formate by Pulsed Potential Electrolysis

2023-05-28T08:35:54+00:00May 28th, 2023|Categories: Publications|Tags: |

Tin disulfide (SnS2) is a promising candidate for electrosynthesis of CO2-to-formate while the low activity and selectivity remain a great challenge. Herein, we report the potentiostatic and pulsed potential CO2RR performance of SnS2 nanosheets (NSs) with tunable S-vacancy and exposure of Sn-atoms or S-atoms prepared controllably by calcination of SnS2 at different temperatures under the H2/Ar atmosphere. The catalytic activity of S-vacancy SnS2 (Vs-SnS2) is improved 1.8 times, but it exhibits an exclusive hydrogen evolution with about 100% FE under all potentials investigated in the static conditions. The theoretical calculations reveal that the adsorption of *H on the Vs-SnS2 surface is energetically more favorable than the carbonaceous intermediates, resulting in active site coverage that hinders the carbon intermediates from being adsorbed. Fortunately, the main product can be switched from hydrogen to formate by applying pulsed potential electrolysis benefiting from in situ formed partially oxidized SnS2-x with the oxide phase selective to formate and the S-vacancy to hydrogen. This work highlights not only the Vs-SnS2 NSs lead to exclusively H2 formation, but also provides insights into the systematic design of highly selective CO2 reduction catalysts reconstructed by pulsed potential electrolysis.

Published in: "Angewandte Chemie International Edition".

Semiconductor SERS on Colourful Substrates with Fabry–Pérot Cavities

2023-02-01T13:07:53+00:00February 1st, 2023|Categories: Publications|Tags: |

Non-metallic materials have emerged as a new family of active substrates for surface-enhanced Raman scattering (SERS), with unique advantages over their metal counterparts. However, owing to their inefficient interaction with the incident wavelength, the Raman enhancement achieved with non-metallic materials is considerably lower with respect to the metallic ones. Herein, we propose colourful semiconductor-based SERS substrates for the first time by utilizing a Fabry–Pérot cavity, which realize a large freedom in manipulating light. Owing to the delicate adjustment of the absorption in terms of both frequency and intensity, resonant absorption can be achieved with a variety of non-metal SERS substrates, with the sensitivity further enhanced by ~100 times. As a typical example, by introducing a Fabry–Pérot-type substrate fabricated with SiO2/Si, a rather low detection limit of 10−16 M for the SARS-CoV-2S protein is achieved on SnS2. This study provides a realistic strategy for increasing SERS sensitivity when semiconductors are employed as SERS substrates.

Published in: "Angewandte Chemie International Edition".

Near-Infrared plasmon induced hot electron extraction evidence in an indium tin oxide nanoparticle / monolayer molybdenum disulphide heterostructure. (arXiv:2207.04195v1 [physics.optics])

2022-07-12T04:30:19+00:00July 12th, 2022|Categories: Publications|Tags: , , |

In this work, we observe plasmon induced hot electron extraction in a heterojunction between indium tin oxide nanocrystals and monolayer molybdenum disulphide. We study the sample with ultrafast differential transmission exciting the sample at 1750 nm where the intense localized plasmon surface resonance of the indium tin oxide nanocrystals is and where the monolayer molybdenum disulphide does not absorb light. With the excitation at 1750 nm we observe the excitonic features of molybdenum disulphide in the visible range, close to the exciton of molybdenum disulphide. Such phenomenon can be ascribed to a charge transfer between indium tin oxide nanocrystals and monolayer molybdenum disulphide upon plasmon excitation. These results are a first step towards the implementation of near infrared plasmonic materials for photoconversion.

Published : "arXiv Mesoscale and Nanoscale Physics".

Bandgap Shrinkage and Charge Transfer in 2D Layered SnS2 Doped with V for Photocatalytic Efficiency Improvement

2021-11-26T13:23:50+00:00November 26th, 2021|Categories: Publications|Tags: , |

The interstitially tetrahedral O–V–S site in the vdW gap of V-doped 2D SnS2 establishes the origin of the charge transfer mechanism between metal ion V4+ 3d and ligand O2- 2p/S2- 3p states and the decrease in the band gap by studying synchrotron-based techniques and first-principles density functional theory. Abstract Effects of electronic and atomic structures of V-doped 2D layered SnS2 are studied using X-ray spectroscopy for the development of photocatalytic/photovoltaic applications. Extended X-ray absorption fine structure measurements at V K-edge reveal the presence of VO and VS bonds which form the intercalation of tetrahedral OVS sites in the van der Waals (vdW) gap of SnS2 layers. X-ray absorption near-edge structure (XANES) reveals not only valence state of V dopant in SnS2 is ≈4+ but also the charge transfer (CT) from V to ligands, supported by V L α,β resonant inelastic X-ray scattering. These results suggest V doping produces extra interlayer covalent interactions and additional conducting channels, which increase the electronic conductivity and CT. This gives rapid transport of photo-excited electrons and effective carrier separation in layered SnS2. Additionally, valence-band photoemission spectra and S K-edge XANES indicate that the density of states near/at valence-band maximum is shifted to lower binding energy in V-doped SnS2 compare to pristine SnS2 and exhibits band gap shrinkage. These findings support first-principles density functional theory calculations of the interstitially tetrahedral OVS site intercalated in the vdW gap, highlighting the CT from V to ligands in V-doped SnS2.

Published in: "Small".

Low Optical Writing Energy Multibit Optoelectronic Memory Based on SnS2/h‐BN/Graphene Heterostructure

2021-11-26T13:21:24+00:00November 26th, 2021|Categories: Publications|Tags: , , , |

Multibit optoelectronic memory based on 2D materials may break through the bottleneck of the performance degradation. The SnS2/h-BN/graphene floating gate memory shows great performances in both electrical program and optical program modes. The ultralow hole barrier height between SnS2 and h-BN causes low optical writing energy compared to the other common 2D semiconductors devices. Abstract With the rapid development of artificial intelligence and neural network computing, the requirement for information storage in computing is gradually increasing. Floating gate memories based on 2D materials has outstanding characteristics such as non-volatility, optical writing, and optical storage, suitable for application in photonic in-memory computing chips. Notably, the optoelectronic memory requires less optical writing energy, which means lower power consumption and greater storage levels. Here, the authors report an optoelectronic memory based on SnS2/h-BN/graphene heterostructure with an extremely low photo-generated hole tunneling barrier of 0.23 eV. This non-volatile multibit floating gate memory shows a high switching ratio of 106 and a large memory window range of 64.8 V in the gate range ±40 V. And the memory device can achieve multilevel storage states of 50 under a low power light pulses of 0.32 nW and small light pulse width of 50 ms. Thanks to the Fowler–Nordheim tunneling of the photo-generated holes, the optical writing energy of the optoelectronic memory has been successfully reduced by one to three orders of magnitude compared to existing 2D materials-based systems.

Published in: "Small".

Low Thermal Conductivity and Interface Thermal Conductance in SnS2. (arXiv:2111.08310v1 [cond-mat.mtrl-sci])

2021-11-17T02:29:45+00:00November 17th, 2021|Categories: Publications|Tags: , , |

After the discovery of graphene, there have been tremendous efforts in exploring various layered two-dimensional (2D) materials for their potential applications in electronics, optoelectronics, as well as energy conversion and storage. One of such 2D materials, SnS2, which is earth abundant, low in toxicity, and cost effective, has been reported to show a high on/off current ratio, fast photodetection, and high optical absorption, thus making this material promising for device applications. Further, a few recent theoretical reports predict high electrical conductivity and Seebeck coefficient in its bulk counterparts. However, the thermal properties of SnS2 have not yet been properly explored, which are important to materialize many of its potential applications. Here, we report the thermal properties of SnS2 measured using the optothermal method and supported by density functional theory (DFT) calculations. Our experiments suggest very low in-plane lattice thermal conductivity (k{appa} = 3.20 +- 0.57 W m-1 K-1) and cross-plane interfacial thermal conductance per unit area (g = 0.53 +- 0.09 MW m-2 K-1) for monolayer SnS2 supported on a SiO2/Si substrate. The thermal properties show a dependence on the thickness of the SnS2 flake. Based on the findings of our DFT calculations, the very low value of the lattice thermal conductivity can be attributed to low group velocity, a shorter lifetime of the phonons, and strong anharmonicity in the crystal. Materials with low thermal conductivity are important for thermoelectric applications as the thermoelectric power coefficient goes inversely with the thermal conductivity.

Published in: "arXiv Material Science".

Dynamic Restructuring of Cu‐Doped SnS2 Nanoflowers for Highly Selective Electrochemical CO2 Reduction to Formate

2021-09-30T13:07:43+00:00September 30th, 2021|Categories: Publications|Tags: , |

With ever-increasing energy consumption and continuous rise in atmospheric CO 2 concentration, electrochemical reduction of CO 2 into chemicals/fuels is becoming a promising yet challenging solution. Sn-based materials are identified as attractive electrocatalysts for CO 2 reduction reaction (CO 2 RR) to formate but suffer from insufficient selectivity and activity, especially at large cathodic current densities. In this work, we demonstrate that Cu-doped SnS 2 nanoflowers can undergo in situ dynamic restructuring to generate catalytically active S-doped Cu/Sn alloy for highly selective electrochemical CO 2 RR to formate over a wide potential window. Theoretical thermodynamic analysis of reaction energetics indicates that the optimal electronic structure of the Sn active site can be regulated by both S-doping and Cu-alloying to favor formate formation, while the CO and H 2 pathways will be suppressed. Our findings provide a rational strategy on electronic modulation of metal active site(s) for designing active and selective electrocatalysts towards CO 2 RR.

Published in: "Angewandte Chemie International Edition".

Hetero-structure Mode Space Method for Efficient Device Simulations. (arXiv:2107.10511v1 [cond-mat.mes-hall])

2021-07-23T04:30:27+00:00July 23rd, 2021|Categories: Publications|Tags: , |

The Hamiltonian size reduction method or the mode space method applicable to general heterogeneous structures is developed in this work. The effectiveness and accuracy of the method are demonstrated for four example devices of GaSb/InAs tunnel field effect transistor (FET), MoTe2/SnS2 bilayer vertical FET, InAs nanowire FET with a defect, and Si nanowire FET with rough surfaces. The Hamiltonian size is reduced to around 5 % of the original full Hamiltonian size without losing the accuracy of the calculated transmission and local density of states in a practical sense. The method developed in this work can be used with any type of Hamiltonian and can be applied to virtually any hetero-structure, so it has the potential to become an enabling technology for efficient simulations of hetero-structures.

Published : "arXiv Mesoscale and Nanoscale Physics".

Intercorrelated ferroelectrics in 2D van der Waals materials. (arXiv:2011.10914v1 [cond-mat.mtrl-sci])

2020-11-24T02:29:39+00:00November 24th, 2020|Categories: Publications|Tags: , , , , |

2D intercorrelated ferroelectrics, exhibiting a coupled in-plane and out-of-plane ferroelectricity, is a fundamental phenomenon in the field of condensed-mater physics. The current research is based on the paradigm of bi-directional inversion asymmetry in single-layers, which restricts 2D intercorrelated ferroelectrics to extremely few systems. Herein, we propose a new scheme for achieving 2D intercorrelated ferroelectrics using van der Waals (vdW) interaction, and apply this scheme to a vast family of 2D vdW materials. Using first-principles, we demonstrate that 2D vdW multilayers-for example, BN, MoS2, InSe, CdS, PtSe2, TI2O, SnS2, Ti2CO2 etc.- can exhibit coupled in-plane and out-of-plane ferroelectricity, thus yielding 2D intercorrelated ferroelectricsferroelectric physics. We further predict that such intercorrelated ferroelectrics could demonstrate many distinct properties, for example, electrical full control of spin textures in trilayer PtSe2 and electrical permanent control of valley-contrasting physics in four-layer VS2. Our finding opens a new direction for 2D intercorrelated ferroelectric research.

Published in: "arXiv Material Science".

Hybridization of Defective Tin Disulfide Nanosheets and Silver Nanowires Enables Efficient Electrochemical Reduction of CO2 into Formate and Syngas

2019-12-14T04:33:21+00:00December 14th, 2019|Categories: Publications|Tags: |

The hybridized composite of defective SnS2 nanosheets and Ag nanowires is developed for CO2 electrochemical reduction. The Ag‐SnS2 hybrid nanosheets display 38.8 mA cm−2 of geometrical current density at –1.0 V vs reversible hydrogen electrode, including 23.3 mA cm−2 for formate and 15.5 mA cm−2 for syngas with the CO/H2 ratio of 1:1. Abstract Integrating the defect engineering and conductivity promotion represents a promising way to improve the performance of CO2 electrochemical reduction. Herein, the hybridized composite of defective SnS2 nanosheets and Ag nanowires is developed as an efficient catalyst for the production of formate and syngas toward CO2 electrochemical reduction. The Schottky barrier in Ag‐SnS2 hybrid nanosheets is negligible due to the similar Fermi level of SnS2 nanosheets and Ag nanowires. Accordingly, the free electrons of Ag nanowires participate in the electronic transport of SnS2 nanosheets, and thus give rise to a 5.5‐fold larger carrier density of Ag‐SnS2 hybrid nanosheets than that of SnS2 nanosheets. In CO2 electrochemical reduction, the Ag‐SnS2 hybrid nanosheets display 38.8 mA cm−2 of geometrical current density at –1.0 V vs reversible hydrogen electrode, including 23.3 mA cm−2 for formate and 15.5 mA cm−2 for syngas with the CO/H2 ratio of 1:1. A mechanistic study reveals that the abundant defect sites and carrier density not only promote the conductivity of the electrocatalyst, but also increase the binding strength for CO2, which account for the efficient CO2 reduction.

Published in: "Small".

Template‐Assisted Synthesis of Metallic 1T′‐Sn0.3W0.7S2 Nanosheets for Hydrogen Evolution Reaction

2019-12-03T06:33:08+00:00December 3rd, 2019|Categories: Publications|Tags: |

Sn1− xW xS2 alloys are synthesized with 1T SnS2 as the template by adjusting the molar ratios of precursors. The Sn0.3W0.7S2 alloy shows up to 83% metallic properties and possess a distorted octahedral coordination 1T′ phase structure. Metallic 1T′‐Sn0.3W0.7S2 endows a markedly enhanced hydrogen evolution reaction (HER) performance. The auxiliary of carbon black further effectively improves HER, catalytic performance rarely attenuates, and structure morphology remains stable. Abstract Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn1− xW xS2 alloys can be formed by combining W with 1T tin disulfide (SnS2) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn1− xW xS2 alloys with varying x are prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn0.3W0.7S2 displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn0.3W0.7S2 has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn0.3W0.7S2 coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS2. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging

Published in: "Advanced Functional Materials".

Template‐Assisted Synthesis of Metallic 1T′‐Sn0.3W0.7S2 Nanosheets for Hydrogen Evolution Reaction

2019-12-03T02:32:29+00:00December 3rd, 2019|Categories: Publications|Tags: |

Sn1− xW xS2 alloys are synthesized with 1T SnS2 as the template by adjusting the molar ratios of precursors. The Sn0.3W0.7S2 alloy shows up to 83% metallic properties and possess a distorted octahedral coordination 1T′ phase structure. Metallic 1T′‐Sn0.3W0.7S2 endows a markedly enhanced hydrogen evolution reaction (HER) performance. The auxiliary of carbon black further effectively improves HER, catalytic performance rarely attenuates, and structure morphology remains stable. Abstract Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn1− xW xS2 alloys can be formed by combining W with 1T tin disulfide (SnS2) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn1− xW xS2 alloys with varying x are prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn0.3W0.7S2 displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn0.3W0.7S2 has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn0.3W0.7S2 coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS2. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging

Published in: "Advanced Functional Materials".

Template‐Assisted Synthesis of Metallic 1T′‐Sn0.3W0.7S2 Nanosheets for Hydrogen Evolution Reaction

2019-11-28T04:31:38+00:00November 28th, 2019|Categories: Publications|Tags: |

Sn1− xW xS2 alloys are synthesized with 1T SnS2 as the template by adjusting the molar ratios of precursors. The Sn0.3W0.7S2 alloy shows up to 83% metallic properties and possess a distorted octahedral coordination 1T′ phase structure. Metallic 1T′‐Sn0.3W0.7S2 endows a markedly enhanced hydrogen evolution reaction (HER) performance. The auxiliary of carbon black further effectively improves HER, catalytic performance rarely attenuates, and structure morphology remains stable. Abstract Crystal phase control still remains a challenge for the precise synthesis of 2D layered metal dichalcogenide (LMD) materials. The T′ phase structure has profound influences on enhancing electrical conductivity, increasing active sites, and improving intrinsic catalytic activity, which are urgently needed for enhancing hydrogen evolution reaction (HER) activity. Theoretical calculations suggest that metastable T′ phase 2D Sn1− xW xS2 alloys can be formed by combining W with 1T tin disulfide (SnS2) as a template to achieve a semiconductor‐to‐metallic transition. Herein, 2D Sn1− xW xS2 alloys with varying x are prepared by adjusting the molar ratio of reactants via hydrothermal synthesis, among which Sn0.3W0.7S2 displays a maximum of concentration of 81% in the metallic phase and features a distorted octahedral‐coordinated metastable 1T′ phase structure. The obtained 1T′‐Sn0.3W0.7S2 has high intrinsic electrical conductivity, lattice distortion, and defects, showing a prominently improved HER catalytic performance. Metallic Sn0.3W0.7S2 coupled with carbon black exhibits at least a 215‐fold improvement compared to pristine SnS2. It has excellent long‐term durability and HER activity. This work reveals a general phase transition strategy by using T phase materials as templates and merging

Published in: "Advanced Functional Materials".

Highly sensitive NO 2 gas sensors based on hexagonal SnS 2 nanoplates operating at room temperature

2019-11-21T10:34:11+00:00November 21st, 2019|Categories: Publications|Tags: |

While continuously developing high-performance chemoresistive gas sensors, reducing device power consumption is not negligible. One of the most efficient ways is to enable gas sensors to work close to room temperature. In this work, we present a gas sensor based on hexagonal tin disulfide (SnS 2 ) nanoplates for sensitive and reversible NO 2 sensing at room temperature. Two-dimensional SnS 2 nanoplates are synthesized via a facile hydrothermal method using Triton X-100 as a surfactant. The sensor exhibits a high response of 15.6 for 50 ppm NO 2 with an experimental limit of detection of 50 ppb at room temperature. Besides, excellent linearity, outstanding selectivity, and reliable long-term stability within 40 d are also demonstrated during the experiment process. The sensing mechanism of this sensor could be explained as the physisorption and charge transfer between NO 2 molecules and SnS 2 nanoplates, which make it pos…

Published in: "Nanotechnology".

Hybridization of Defective Tin Disulfide Nanosheets and Silver Nanowires Enables Efficient Electrochemical Reduction of CO2 into Formate and Syngas

2019-11-13T00:33:28+00:00November 12th, 2019|Categories: Publications|Tags: |

The hybridized composite of defective SnS2 nanosheets and Ag nanowires is developed for CO2 electrochemical reduction. The Ag‐SnS2 hybrid nanosheets display 38.8 mA cm−2 of geometrical current density at –1.0 V vs reversible hydrogen electrode, including 23.3 mA cm−2 for formate and 15.5 mA cm−2 for syngas with the CO/H2 ratio of 1:1. Abstract Integrating the defect engineering and conductivity promotion represents a promising way to improve the performance of CO2 electrochemical reduction. Herein, the hybridized composite of defective SnS2 nanosheets and Ag nanowires is developed as an efficient catalyst for the production of formate and syngas toward CO2 electrochemical reduction. The Schottky barrier in Ag‐SnS2 hybrid nanosheets is negligible due to the similar Fermi level of SnS2 nanosheets and Ag nanowires. Accordingly, the free electrons of Ag nanowires participate in the electronic transport of SnS2 nanosheets, and thus give rise to a 5.5‐fold larger carrier density of Ag‐SnS2 hybrid nanosheets than that of SnS2 nanosheets. In CO2 electrochemical reduction, the Ag‐SnS2 hybrid nanosheets display 38.8 mA cm−2 of geometrical current density at –1.0 V vs reversible hydrogen electrode, including 23.3 mA cm−2 for formate and 15.5 mA cm−2 for syngas with the CO/H2 ratio of 1:1. A mechanistic study reveals that the abundant defect sites and carrier density not only promote the conductivity of the electrocatalyst, but also increase the binding strength for CO2, which account for the efficient CO2 reduction.

Published in: "Small".

Large‐Scale Growth and Field‐Effect Transistors Electrical Engineering of Atomic‐Layer SnS2

2019-10-17T00:33:53+00:00October 17th, 2019|Categories: Publications|Tags: , |

Large‐scale (over 410 µm) SnS2 atomic layers, whose field‐effect transistors show a high on/off ratio of 108 and carrier mobility of 2.58 cm2 V–1 s–1, are successfully synthesized by a scalable salt‐assisted chemical vapor deposition method. The effect of temperature on the electrical properties is systematically investigated, suggesting the scattering mechanism transforms from charged impurities scattering to electron–phonon scattering. Abstract 2D layers of metal dichalcogenides are of considerable interest for high‐performance electronic devices for their unique electronic properties and atomically thin geometry. 2D SnS2 nanosheets with a bandgap of ≈2.6 eV have been attracting intensive attention as one potential candidate for modern electrocatalysis, electronic, and/or optoelectronic fields. However, the controllable growth of large‐size and high‐quality SnS2 atomic layers still remains a challenge. Herein, a salt‐assisted chemical vapor deposition method is provided to synthesize atomic‐layer SnS2 with a large crystal size up to 410 µm and good uniformity. Particularly, the as‐fabricated SnS2 nanosheet‐based field‐effect transistors (FETs) show high mobility (2.58 cm2 V−1 s−1) and high on/off ratio (≈108), which is superior to other reported SnS2‐based FETs. Additionally, the effects of temperature on the electrical properties are systematically investigated. It is shown that the scattering mechanism transforms from charged impurities scattering to electron–phonon scattering with the temperature. Moreover, SnS2 can serve as an ideal material for energy storage and catalyst support. The high performance together with controllable growth of SnS2 endow it with great potential for future applications in electrocatalysis, electronics, and optoelectronics.

Published in: "Small".

Large‐Scale Growth and Field‐Effect Transistors Electrical Engineering of Atomic‐Layer SnS2

2019-10-07T22:36:58+00:00October 7th, 2019|Categories: Publications|Tags: , |

Large‐scale (over 410 µm) SnS2 atomic layers, whose field‐effect transistors show a high on/off ratio of 108 and carrier mobility of 2.58 cm2 V–1 s–1, are successfully synthesized by a scalable salt‐assisted chemical vapor deposition method. The effect of temperature on the electrical properties is systematically investigated, suggesting the scattering mechanism transforms from charged impurities scattering to electron–phonon scattering. Abstract 2D layers of metal dichalcogenides are of considerable interest for high‐performance electronic devices for their unique electronic properties and atomically thin geometry. 2D SnS2 nanosheets with a bandgap of ≈2.6 eV have been attracting intensive attention as one potential candidate for modern electrocatalysis, electronic, and/or optoelectronic fields. However, the controllable growth of large‐size and high‐quality SnS2 atomic layers still remains a challenge. Herein, a salt‐assisted chemical vapor deposition method is provided to synthesize atomic‐layer SnS2 with a large crystal size up to 410 µm and good uniformity. Particularly, the as‐fabricated SnS2 nanosheet‐based field‐effect transistors (FETs) show high mobility (2.58 cm2 V−1 s−1) and high on/off ratio (≈108), which is superior to other reported SnS2‐based FETs. Additionally, the effects of temperature on the electrical properties are systematically investigated. It is shown that the scattering mechanism transforms from charged impurities scattering to electron–phonon scattering with the temperature. Moreover, SnS2 can serve as an ideal material for energy storage and catalyst support. The high performance together with controllable growth of SnS2 endow it with great potential for future applications in electrocatalysis, electronics, and optoelectronics.

Published in: "Small".

Amorphous Sn/Crystalline SnS2 Nanosheets via In Situ Electrochemical Reduction Methodology for Highly Efficient Ambient N2 Fixation

2019-10-03T22:34:03+00:00October 3rd, 2019|Categories: Publications|Tags: |

An amorphous Sn/crystalline SnS2 nanosheet is synthesized by an L‐cysteine‐based hydrothermal process followed by in situ electrochemical reduction, which shows excellent performance in the nitrogen reduced reaction with an ammonia production rate of 23.8 µg h−1 mg−1 at −0.8 V versus reversible hydrogen electrode (RHE) and Faradaic efficiency of 6.5% at −0.7 V versus RHE. Abstract Electrochemical nitrogen reduction reaction (NRR) as a new strategy for synthesizing ammonia has attracted ever‐growing attention, due to its renewability, flexibility, and sustainability. However, the lack of efficient electrocatalysts has hampered the development of such reactions. Herein, a series of amorphous Sn/crystalline SnS2 (Sn/SnS2) nanosheets by an L‐cysteine‐based hydrothermal process, followed by in situ electrochemical reduction, are synthesized. The amount of reduced amorphous Sn can be adjusted by selecting electrolytes with different pH values. The optimized Sn/SnS2 catalyst can achieve a high ammonia yield of 23.8 µg h−1 mg−1, outperforming most reported noble‐metal NRR electrocatalysts. According to the electrochemical tests, the conversion of SnS2 to an amorphous Sn phase leads to the substantial increase of its catalytic activity, while the amorphous Sn is identified as the active phase. These results provide a guideline for a rational design of low‐cost and highly active Sn‐based catalysts thus paving a wider path for NRR.

Published in: "Small".

SnS2/Co3S4 Hollow Nanocubes Anchored on S‐Doped Graphene for Ultrafast and Stable Na‐Ion Storage

2019-10-03T22:33:50+00:00October 3rd, 2019|Categories: Publications|Tags: , , |

Nanocube‐shaped SnS2/Co3S4‐rGO composites are synthesized for the first time via coprecipitation of Sn4+, Co2+, and OH− followed by alkaline etching and hydrothermal methods. The SnS2/Co3S4‐rGO electrode exhibits a high reversible capacity (1141.8 mAh g−1 at 0.1 A g−1 after 50 cycles) and excellent rate performance (392.9 mAh g−1 at 10 A g−1) when used as an anode for sodium‐ion batteries. Abstract SnS2 has been widely studied as an anode material for sodium‐ion batteries (SIBs) based on the high theoretical capacity and layered structure. Unfortunately, rapid capacity decay associated with volume variation during cycling limits practical application. Herein, SnS2/Co3S4 hollow nanocubes anchored on S‐doped graphene are synthesized for the first time via coprecipitation and hydrothermal methods. When applied as the anode for SIBs, the sample delivers a distinguished charge specific capacity of 1141.8 mAh g−1 and there is no significant capacity decay (0.1 A g−1 for 50 cycles). When the rate is increased to 0.5 A g−1, it presents 845.7 mAh g−1 after cycling 100 times. Furthermore, the composite also exhibits an ultrafast sodium storage capability where 392.9 mAh g−1 can be obtained at 10 A g−1 and the charging time is less than 3 min. The outstanding electrochemical properties can be ascribed to the enhancement of conductivity for the addition of S‐doped graphene and the existence of p–n junctions in the SnS2/Co3S4 heterostructure. Moreover, the presence of mesopores between nanosheets can alleviate volume expansion during cycling as well as being beneficial for the migration of Na+.

Published in: "Small".

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