Large-area (~cm 2 ) films of vertical heterostructures formed by alternating graphene and transition-metal dichalcogenide (TMD) alloys are obtained by wet chemical routes followed by a thermal treatment at low temperature. In particular, we synthesized stacked graphene and WxMo1-xS2 alloy phases that were used as hydrogen evolution catalysts. We observed a Tafel slope of 38.7 mV dec -1 and 96 mV onset potential (at current density of 10 mA cm -2 ) when the heterostructure alloy was annealed at 300 o C. These results indicate that heterostructures formed by graphene and W0.4Mo0.6S2 alloys are far more efficient than WS2 and MoS2 by at least a factor of two, and they are superior than other reported TMD systems. This strategy offers a cheap and low temperature synthesis alternative able to replace Pt in the hydrogen evolution reaction (HER). Furthermore, the catalytic activity of the alloy is stable over time,i.e. the catalytic activity does not experience a significant change even after 1000 cycles. Using density functional theory calculations, we found that this enhanced hydrogen evolution in the 4 WxMo1-xS2 alloys is mainly due to the lower energy barrier created by a favorable overlap of the d-orbitals from the transition metals and the s-orbitals of H2; with the lowest energy barrier occurring for the W0.4Mo0.6S2 alloy. Thus, it is now possible to further improve the performance of the "inert" TMD basal plane via metal alloying, in addition to the previously reported strategies such as creation of point defects, vacancies and edges. The synthesis of graphene/W0.4Mo0.6S2 produced at relatively low temperatures is scalable and could be used as an effective low cost Pt-free catalyst.5

This review describes state-of-the-art scientific and technological developments of electrospun nanofibers and their use in self-cleaning membranes, responsive smart materials, and other related applications.Superhydrophobic self-cleaning, also called the lotus effect, utilizes the right combinations of surface chemistry and topology to form a very high contact angle on a surface and drive water droplets away from it. The high-contact-angle water droplets easily roll off the surface, carrying with them dirt, particles, and other contaminants by way of gravity. A brief introduction to the theory of superhydrophobic self-cleaning and the basic principles of the electrospinning process is presented. Also discussed is electrospinning for the purpose of creating superhydrophobic self-cleaning surfaces under a wide variety of parameters that allow effective control of roughness of the porous structure with hydrophobic entities. The main principle of electrospinning at the nanoscale and existing difficulties in synthesis of one-dimensional materials by electrospinning are also covered thoroughly. The results of different electrospun nanofibers are compared to each other in terms of their superhydrophobic properties and their scientific and technological applications.

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graphite has a theoretical capacity of 279 mAh g −1 . [3,17] In 2015, Ji and Hu have separately demonstrated the electrochemical intercalation of K ions into graphite in potassium hexafluorophosphate (KPF 6 )/ ethylene carbonate (EC)-diethyl carbonate (DEC) electrolytes. [4,18] However, their works did not achieve a highly reversible K + insertion/extraction process in KPF 6 /EC-DEC electrolyte because the formed solid electrolyte interphase (SEI) becomes fragile and unstable due to the large volume variation (≈60%) during K + insertion/extraction. [19,20] Compared to the conventional lowconcentration electrolyte (LCE), adopting a high-concentration electrolyte (HCE, e.g., >3 m) is a promising strategy to solve the above problem because it possesses some unusual physicochemical and electrochemical properties due to the unique solvation structure of ions, which make it different from an LCE. [21][22][23][24] In 2007, Jeong adopted the concentrated lithium bisperfluoroethylsulfonyl imide LiN(SO 2 C 2 F 5 ) 2 / propylene carbonate (PC) to realize a reversible graphite anode for lithium-ion batteries. [24] Recently, Komaba and Lu have reported the highly reversible graphite anode for PIBs at concentrated potassium bis(fluorosulfonyl)imide (KFSI)/ dimethoxyethane (DME) and KFSI/ethyl methyl carbonate electrolytes, respectively. [25,26] Despite these progresses, the issues of high viscosity, low ionic conductivity, and the increased cost of the HCE still hinder its practical applications. To overcome these disadvantages in using HCE, several groups have added a low-polarity cosolvent to dilute an HCE by forming a localized high-concentration electrolyte (LHCE). It is believed that the introduced cosolvent does not participate in the solvation process. Zhang's group used the bis(2,2,2,-tri-fluoroethyl) ether to dilute the concentrated lithium bis(fluorosulfonyl) imide (LiFSI)/dimethyl carbonate and improve the coulombic efficiency (CE) of lithium metal anodes without dendrite formation. [27] They also diluted concentrated LiFSI in sulfone with a fluorinated ether for high-voltage (4.9 V) lithium metal batteries. [28] Wang's group used the same cosolvent in the concentrated LiFSI/DME to increase both coulombic efficiencies of S cathode and Li anode for Li-S batteries. [29] However, none of the LHCE reported to date has been applied in PIBs, its stability and compatibility with PIBs remain in question.Herein, our work reports for the first time that a highly reversible K + insertion/extraction into graphite interlayer can Reversible intercalation of potassium-ion (K + ) into graphite makes it a promising anode material for rechargeable potassium-ion batteries (PIBs). However, the current graphite anodes in PIBs often suffer from poor cyclic stability with low coulombic efficiency. A stable solid electrolyte interphase (SEI) is necessary for stabilizing the large interlayer expansion during K + insertion. Herein, a localized high-concentration electrolyte (LHCE) is designed by adding a highly fluorinated ether into the con...

Chemical doping constitutes an effective route to alter the electronic, chemical, and optical properties of two-dimensional transition metal dichalcogenides (2D-TMDs). We used a plasma-assisted method to introduce carbon-hydrogen (CH) units into WS2 monolayers. We found CH-groups to be the most stable dopant to introduce carbon into WS2, which led to a reduction of the optical bandgap from 1.98 to 1.83 eV, as revealed by photoluminescence spectroscopy. Aberration corrected high-resolution scanning transmission electron microscopy (AC-HRSTEM) observations in conjunction with first-principle calculations confirm that CH-groups incorporate into S vacancies within WS2. According to our electronic transport measurements, undoped WS2 exhibits a unipolar n-type conduction. Nevertheless, the CH-WS2 monolayers show the emergence of a p-branch and gradually become entirely p-type, as the carbon doping level increases. Therefore, CH-groups embedded into the WS2 lattice tailor its electronic and optical characteristics. This route could be used to dope other 2D-TMDs for more efficient electronic devices.

N-doped graphene can be used as a substrate for different molecules to effectively enhance their Raman scattering signal.

Dilute magnetic semiconductors (DMS), achieved through substitutional doping of spin-polarized transition metals into semiconducting systems, enable experimental modulation of spin dynamics in ways that hold great promise for novel magneto-electric or magneto-optical devices, especially for two-dimensional (2D) systems such as transition metal dichalcogenides that accentuate interactions and activate valley degrees of freedom. Practical applications of 2D magnetism will likely require room-temperature operation, air stability, and (for magnetic semiconductors) the ability to achieve optimal doping levels without dopant aggregation. Here, room-temperature ferromagnetic order obtained in semiconducting vanadium-doped tungsten disulfide monolayers produced by a reliable single-step film sulfidation method across an exceptionally wide range of vanadium concentrations, up to 12 at% with minimal dopant aggregation, is described. These monolayers develop p-type transport as a function of vanadium incorporation and rapidly reach ambipolarity. Ferromagnetism peaks at an intermediate vanadium concentration of˜2 at% and decreases for higher concentrations, which is consistent with quenching due to orbital hybridization at closer vanadium-vanadium spacings, as supported by transmission electron microscopy, magnetometry, and first-principles calculations. Room-temperature 2D-DMS provide a new component to expand the functional scope of van der Waals heterostructures and bring semiconducting magnetic 2D heterostructures into the realm of practical application.

Chemical vapor deposition (CVD) is a scalable method able to synthesize MoS2 and WS2 monolayers. In this work, we reduced the synthesis temperature by 200 °C only by introducing tellurium (Te) into the CVD process. The as-synthesized MoS2 and WS2 monolayers show high phase purity and crystallinity. The optical and electrical performance of these materials is comparable to those synthesized at higher temperatures. We believe this work will accelerate the industrial synthesis of these semiconducting monolayers.