Electronic Properties and Chemical Reactivity of TiS<sub>2</sub> Nanoflakes

Cucinotta, Clotilde S.; Dolui, Kapildeb; Pettersson, Henrik; Ramasse, Quentin M.; Long, Edmund; O’Brian, Sean E.; Nicolosi, Valeria; Sanvito, Stefano

doi:10.1021/acs.jpcc.5b03212

Cited by 50 publications

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“…During stage 1, sulphur in the outermost surface regions is exchanged with oxygen to produce the hydrogen sulphide smelled upon opening vials of the dispersion. This has previously been demonstrated theoretically, 15 and the mechanism reproduced in Supplementary Fig. 7.…”

Section: Possible Oxidation Mechanismsupporting

confidence: 80%

“…Calculations have shown the band gap can be fine-tuned between the extremes of pure TiS 2 and TiO 2 via oxygen substitution, 15 which might also explain why such a range of values exist for the measured band-gap. Aging in water would provide one method of controlling the formation of oxide, although it would be isolated to the edges.…”

Section: Oxidation By Watermentioning

confidence: 99%

“…Generation of a sulphur vacancy is strongly endothermic however (−1.4 eV) and under the proposed mechanism, filling one would not result in the formation of a new vacancy (in contrast to the chaining reaction with water). 15 Filling a vacancy would also result in the formation of a lone oxygen atom that would then either need a second vacancy to enter the structure, or combination with another lone oxygen atom to form a new O 2 molecule (we did not investigate this step). The low reactivity of O 2 at room temperature is therefore believed to be due to the relatively large barrier in bringing O 2 to the surface and then removing a sulphur atom, which is easier to overcome as thermal energy becomes more plentiful upon heating.…”

Section: Oxidation By Watermentioning

confidence: 99%

“…Cucinotta et al 15 performed density functional theory (DFT) calculations on the above reactions, predicting that in an aqueous environment water would preferentially oxidise a monolayer from the edge or from a point defect in the case that the edge was 50% terminated in sulphur. It is worth noting that other possible mechanisms could result in the formation of different species including SO 2 , but this was not included in these calculations.…”

Section: Introductionmentioning

confidence: 99%

“…This nanoflake was created to study structural and oxidation properties at the edges, which were modelled with 50% S-passivation. 15 The structure of this edge was a zig-zag structure, with S atoms lying across the Ti terminal row such that the edge appears tilted. This has the effect of leaving the Ti atoms accessible to the oxidising molecules-gaseous oxygen and water.…”

mentioning

confidence: 99%

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An in situ and ex situ TEM study into the oxidation of titanium (IV) sulphide

et al. 2017

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Titanium (IV) sulphide (TiS 2 ) is a layered transition metal dichalcogenide, which we exfoliate using liquid phase exfoliation. TiS 2 is a candidate for being part of a range of future technologies. These applications are varied, and include supercapacitor and battery energy storage devices, catalytic substrates and the splitting of water. The driving force behind our interest was as a material for energy storage devices. Here we investigate a potential failure mechanism for such devices, namely oxidation and subsequent loss of sulphur. This degradation is important to understand, since these applications are highly property-dependent, and changes to the chemistry will result in changes in desired properties. Two approaches to study oxidisation were taken: ex situ oxidation by water and oxygen at room temperature and in situ oxidation by a 5% O 2 /Ar gas at elevated temperatures. Both sources of oxygen resulted in oxidation of the starting TiS 2 flakes, with differing morphologies. Water produced amorphous oxide slowly growing in from the edge of the flakes. Oxygen gas at ≥375°C produced crystalline oxide, with a range of structures due to oxidation initiating from various regions of the observed flakes. npj 2D Materials and Applications (2017) 1:22 ; doi:10.1038/s41699-017-0024-4 INTRODUCTION Titanium (IV) sulphide, TiS 2 , is a candidate for applications in a range of future technologies, including catalytic substrates and the splitting of water, supercapacitors and energy storage devices. TiS 2 is a layered transition metal dichalcogenide (TMD) with hexagonal crystal symmetry and takes the 1T phase and is relatively under explored in two-dimensional form. Each layer consists of three sheets of atoms: the two outer planes are sulphur, coordinated to three titanium atoms with a trigonal pyramidal geometry; the middle plane is titanium and each atom takes octahedral coordination to six sulphur atoms. These atomic sheets are stacked ABC (Supplemental Information Fig. 1), while the layers themselves stack AA in the 1T phase.The excellent capacitive properties of bulk TiS 2 (high energydensity and power-density 1, 2 and excellent electronic conductivity 3 ) have attracted interest since the 1970s, with bulk TiS 2 used as a cathode material in lithium-metal/alloy anode batteries, where lithium metal ions were intercalated, transferring charge to reduce titanium 3d orbitals and causing reduction from Ti 4+ to Ti 3+ (refs. 4, 5). High rates of charging and discharging were demonstrated with near-perfect reversibility. In addition, the material forms a single phase with lithium (Li x TiS 2 ) over the entirety of the range 0 ≤ x ≤ 1, avoiding the need for phase changes upon (de-) lithiation which removes much of the strain induced in cycling, prolonging battery life. However, TMD/Lithium-metal batteries were withdrawn from consumers due to accidents in 1989 where the metallic lithium caught fire as a consequence of shortcircuiting due to lithium-dendrite growth.

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Section: Possible Oxidation Mechanismsupporting

confidence: 80%

Section: Oxidation By Watermentioning

confidence: 99%

Section: Oxidation By Watermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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An in situ and ex situ TEM study into the oxidation of titanium (IV) sulphide

et al. 2017

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2D Group IVB Transition Metal Dichalcogenides

Yan

Gong

Wangyang

et al. 2018

Adv Funct Materials

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Semiconductor technology is currently impaired by the surface dangling bond of materials, which introduces scattering and interface traps. 2D materials, especially transition metal dichalcogenides (TMDs) with different main groups, have settled this issue by utilizing unique atomically smooth surfaces and van der Waals (vdW) structures. Over the past few decades, many processes for exploring new materials, manipulating physical properties, and synthesizing single crystals have been developed. Among these 2D materials, group IVB TMDs are distinguished for their splendid physical properties, including ultrahigh mobility, charge density wave, superconducting transitions, etc. Here, the recent advances in group IVB TMDs are reviewed, which offer easy access to next generation nano-, opto-, thermal-electronic, energy storage and conversion applications. Both the advantages and challenges of these studies are summarized to further clarify existing problems.such as ZrSe 2 is up to 8000 µA µm −1 , which is 10 3 times higher than that of MoS 2 . [11] Group IVB TMDs are also promising thermoelectric materials for their enhanced thermoelectric performance with a high power factor such as TiS 2 . [12][13][14][15][16] These features indicate the great potential of group IVB TMDs for adoption into electronics. In addition, group IVB TMDs show fascinating electrochemical performances as hold materials [17][18][19] or electrodes [20,21] in catalysis [22,23] and batteries [24,25] (Figure 1). A breakthrough may be introduced in nanoelectronic and energy fields for ultrahigh performances and nontoxicity of 2D group IVB TMDs.In this review, we focus on the electronic structures of 1T-phase group IVB TMDs, the abundant properties of group IVB TMDs, and their applications in electronic devices. In particular, we start with the unique crystal structures and calculated electronic structures of 2D group IVB dichalcogenides. Then, the great properties and the current studies in electronic devices are reviewed with an emphasis on recently reported transistor and photodetectors based on group IVB TMD nanosheets. In the third part, the synthesis of group IVBs nanostructures is described. We review the current approaches for the isolation of ultrathin sheets and analyze the advantages and drawbacks of various preparation methods. At last, we present the challenges and future prospects of group IVB TMDs. Crystal and Electronic StructuresThe electronic structures of 2D TMDs strongly depend on their crystal structures and d-electron counts. Another crucial feature is the partially filled d bands of transition metals. Bulk TMDs are composed of ordered stacking monolayers connected by the weak van der Waals (vdW) interaction. This kind of layered material exists multifarious in polymorphs and commonly crystallize into three different structures in 1T, 2H, and 3R phases. For group IVB TMDs, 1T phase is more stable than 2H phase in reversal of group VIB TMDs due to their lower formation energies. [23] Figure 2a,b depicts the two typical structures o...

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A first-principles study: single-layer TiS2 modified by non-metal doping

et al. 2022

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In this paper, the effect of substitutional doping of boron (B), carbon (C), nitrogen (N), oxygen (O), and phosphorus (P) at the S-site on the electronic structure of the monolayer TiS 2 system is investigated using a rst-principles calculation method. The system's stability, electronic structure, and charge transfer were analyzed. By calculating the electron cloud overlap population and formation energy, we con rmed that the system is stable, and the Ti-X bond length of the doped system undergoes different degrees of distortion. The properties of the B, C and N doped system show different properties with different doping concentrations; the bandgap of the O-atom system gradually expands with the rise of the doping rate.The hybridization positions of the impurity and the intrinsic atoms are found by comparing the DOS; combined with the charge density difference, we con rmed the interaction of impurity atoms with the system and revealed the bonding process of different systems.

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Electronic Properties and Chemical Reactivity of TiS₂ Nanoflakes

Cited by 50 publications

References 37 publications

An in situ and ex situ TEM study into the oxidation of titanium (IV) sulphide

An in situ and ex situ TEM study into the oxidation of titanium (IV) sulphide

2D Group IVB Transition Metal Dichalcogenides

A first-principles study: single-layer TiS2 modified by non-metal doping

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Electronic Properties and Chemical Reactivity of TiS2 Nanoflakes

Cited by 50 publications

References 37 publications

An in situ and ex situ TEM study into the oxidation of titanium (IV) sulphide

An in situ and ex situ TEM study into the oxidation of titanium (IV) sulphide

2D Group IVB Transition Metal Dichalcogenides

A first-principles study: single-layer TiS2 modified by non-metal doping

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Electronic Properties and Chemical Reactivity of TiS₂ Nanoflakes