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Journal ArticleDOI

2D layered transition metal dichalcogenides (MoS2): Synthesis, applications and theoretical aspects

TL;DR: In this article, a review summarizes the synthesis of 2D transition metal dichalcogenides (TMDCs) by several techniques, i.e., mechanical and chemical exfoliation, RF-sputtering, atomic layer deposition (ALD) and chemical vapor deposition (CVD), etc.
About: This article is published in Applied Materials Today.The article was published on 2018-12-01. It has received 103 citations till now. The article focuses on the topics: Graphene & Atomic layer deposition.
Citations
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01 Sep 2016
TL;DR: Using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, this study systematically investigated the contributions of crystal structure, edges, and sulfur vacancies to the catalytic activity toward HER and revealed that the phase serves as the key role in determining the HER performance.
Abstract: Molybdenum disulfide (MoS2) is a promising nonprecious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding of the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity toward HER from five representative MoS2 nanosheet samples, including 2H and 1T phase, porous 2H and 1T phase, and sulfur-compensated porous 2H phase. Superior HER catalytic activity was achieved in the porous 1T phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T phase MoS2. A comparative study revealed that the phase serves as the key role in determining the HER performance, as 1T phase MoS2 always outperforms the corresponding 2H phase MoS2 samples, and that both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance spectroscopy and positron annihilation lifetime spectroscopy to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance.

175 citations

Journal ArticleDOI
TL;DR: This work verified that the synthesis of Ni-doped In2O3/WS2 nanofilm provides a new avenue to develop promising hybrids for formaldehyde sensing.
Abstract: A high-performance formaldehyde sensor based on nickel (Ni)-doped indium trioxide (In2O3)/tungsten disulfide (WS2) nanocomposite was demonstrated. An epoxy substrate served as matrix of the Ni-In2O3/WS2 nanocomposite sensor. The material properties of self-assembled Ni-In2O3/WS2 nanoheterostructure were fully characterized and confirmed. The formaldehyde-sensing properties of the Ni-In2O3/WS2 composite were tested at 25 °C. Compared to the In2O3, WS2, and their composite, the Ni-In2O3/WS2 sensor demonstrated significant improvement on the formaldehyde-sensing performance, including a low detection limit of 15 ppb, good selectivity, repeatability, fast detection rate, and a fair logarithmic function toward formaldehyde concentration. The dramatically enhanced sensing performance of Ni-In2O3/WS2 film sensor can be attributed to the Ni ion doping and synergistic interfacial incorporation of In2O3/WS2 heterojunction. The sensitive mechanism of the Ni-In2O3/WS2 film sensor toward formaldehyde is explored through density functional theory (DFT) simulation. This work verified that the synthesis of Ni-doped In2O3/WS2 nanofilm provides a new avenue to develop promising hybrids for formaldehyde sensing.

124 citations

Journal ArticleDOI
TL;DR: MoS2, the second most widely studied two-dimensional nanomaterial, has fascinating physical and chemical properties and thus has a wide variety of applications as mentioned in this paper, and has been getting much attention.
Abstract: MoS2, the second most widely studied two-dimensional nanomaterial, has fascinating physical and chemical properties and thus has a wide variety of applications. MoS2 has been getting much attention...

114 citations

Journal ArticleDOI
TL;DR: A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis as discussed by the authors .
Abstract: A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

72 citations

Journal ArticleDOI
TL;DR: As the most intensely investigated 2D materials in the post‐graphene era, transition metal dichalcogenide nanosheets are comprehensively investigated through their element doping, physical/chemical functionalization, and nanohybridization.
Abstract: The discovery of graphene and subsequent verification of its unique properties have aroused great research interest to exploit diversified graphene-analogous 2D nanomaterials with fascinating physicochemical properties. Through either physical or chemical doping, linkage, adsorption, and hybridization with other functional species into or onto them, more novel/improved properties are readily created to extend/expand their functionalities and further achieve great performance. Here, various functionalized hybridizations by using different types of 2D nanomaterials are overviewed systematically with emphasis on their interaction formats (e.g., in-plane or inter plane), synergistic properties, and enhanced applications. As the most intensely investigated 2D materials in the post-graphene era, transition metal dichalcogenide nanosheets are comprehensively investigated through their element doping, physical/chemical functionalization, and nanohybridization. Meanwhile, representative hybrids with more types of nanosheets are also presented to understand their unique surface structures and address the special requirements for better applications. More excitingly, the van der Waals heterostructures of diverse 2D materials are specifically summarized to add more functionality or flexibility into 2D material systems. Finally, the current research status and faced challenges are discussed properly and several perspectives are elaborately given to accelerate the rational fabrication of varied and talented 2D hybrids.

68 citations

References
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Journal ArticleDOI
TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.

81,985 citations

Journal ArticleDOI
22 Oct 2004-Science
TL;DR: Monocrystalline graphitic films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands and they exhibit a strong ambipolar electric field effect.
Abstract: We describe monocrystalline graphitic films, which are a few atoms thick but are nonetheless stable under ambient conditions, metallic, and of remarkably high quality. The films are found to be a two-dimensional semimetal with a tiny overlap between valence and conductance bands, and they exhibit a strong ambipolar electric field effect such that electrons and holes in concentrations up to 10 13 per square centimeter and with room-temperature mobilities of ∼10,000 square centimeters per volt-second can be induced by applying gate voltage.

55,532 citations

Journal ArticleDOI
TL;DR: Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena can now be mimicked and tested in table-top experiments.
Abstract: Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications.

35,293 citations

Journal ArticleDOI
07 Jul 1972-Nature
TL;DR: Water photolysis is investigated by exploiting the fact that water is transparent to visible light and cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm.
Abstract: ALTHOUGH the possibility of water photolysis has been investigated by many workers, a useful method has only now been developed. Because water is transparent to visible light it cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm (ref. 1).

27,819 citations

Journal ArticleDOI
TL;DR: In this paper, the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations, are discussed.
Abstract: This article reviews the basic theoretical aspects of graphene, a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations. The Dirac electrons can be controlled by application of external electric and magnetic fields, or by altering sample geometry and/or topology. The Dirac electrons behave in unusual ways in tunneling, confinement, and the integer quantum Hall effect. The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers. Edge (surface) states in graphene depend on the edge termination (zigzag or armchair) and affect the physical properties of nanoribbons. Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties. The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.

20,824 citations