As a new member of the MXene group, 2D Mo2C has attracted considerable interest due to its potential application as electrodes for energy storage and catalysis. The large‐area synthesis of Mo2C film ...is needed for such applications. Here, the one‐step direct synthesis of 2D Mo2C‐on‐graphene film by molten copper‐catalyzed chemical vapor deposition (CVD) is reported. High‐quality and uniform Mo2C film in the centimeter range can be grown on graphene using a Mo–Cu alloy catalyst. Within the vertical heterostructure, graphene acts as a diffusion barrier to the phase‐segregated Mo and allows nanometer‐thin Mo2C to be grown. Graphene‐templated growth of Mo2C produces well‐faceted, large‐sized single crystals with low defect density, as confirmed by scanning transmission electron microscopy (STEM) measurements. Due to its more efficient graphene‐mediated charge‐transfer kinetics, the as‐grown Mo2C‐on‐graphene heterostructure shows a much lower onset voltage for hydrogen evolution reactions as compared to Mo2C‐only electrodes.
The one‐step direct synthesis of a 2D Mo2C‐on‐graphene heterostructure by molten Cu‐catalyzed chemical vapor deposition is reported. Graphene acts as a diffusion barrier to phase‐segregated Mo, thus allowing the thickness of Mo2C to be kinetically controlled. The heterostructure functions as a highly stable electrode in hydrogen evolution reactions.
Owing to their excellent physical and electrical properties, metal–organic framework (MOF) materials with well‐defined supramolecular structures have received extensive research attention. However, ...the fabrication of large‐area two‐dimensional (2D) MOF films is still a significant challenge. Herein, we propose a novel electrochemical (EC) synthesis method for the preparation of large‐area Cu3(HHTP)2 MOF film on single‐crystal Cu (100) anode. The surface reaction was achieved via charge‐induced molecular assembly. The synthesized MOF film exhibited a high crystalline quality with an electrical conductivity of approximately 0.087 S cm−1, which was around 1000 times larger than the previously reported values for the same material prepared by the interface method. In addition, Cu2(MTCP), Cu3(BTPA)2, and Cu3(TPTC)2 MOF films were synthesized on Cu foil with the same strategy, which confirmed the universality of the proposed method. This controllable EC method can be effectively applied to the industrial‐scale production of 2D MOF films on Cu foil.
A controllable electrochemical synthesis method of MOF films is developed, and opens the door to the fabrication of large‐scale 2D MOF films. Industrial‐scale continuous production of large‐scale MOF films may be realized via this technology, which can promote their application in the field of microelectronic devices.
Unresolved problems associated with the production of graphene materials include the need for greater control over layer number, crystallinity, size, edge structure and spatial orientation, and a ...better understanding of the underlying mechanisms. Here we report a chemical vapor deposition approach that allows the direct synthesis of uniform single-layered, large-size (up to 10,000 μm2), spatially self-aligned, and single-crystalline hexagonal graphene flakes (HGFs) and their continuous films on liquid Cu surfaces. Employing a liquid Cu surface completely eliminates the grain boundaries in solid polycrystalline Cu, resulting in a uniform nucleation distribution and low graphene nucleation density, but also enables self-assembly of HGFs into compact and ordered structures. These HGFs show an average two-dimensional resistivity of 609 ± 200 Ω and saturation current density of 0.96 ± 0.15 mA/μm, demonstrating their good conductivity and capability for carrying high current density.
Conductive metal-organic frameworks (MOFs) have performed well in the fields of energy and catalysis, among which two-dimensional (2D) and three-dimensional (3D) MOFs are well-known. Here, we have ...synthesized a one-dimensional (1D) conductive metal-organic framework (MOF) in which hexacoordinated 1,5-Diamino-4,8-dihydroxy-9,10-anthraceneedione (DDA) ligands are connected by double Cu ions, resulting in nanoribbon layers with 1D π-d conjugated nanoribbon plane and out-of-plane π-π stacking, which facilitates charge transport along two dimensions. The DDA-Cu as a highly conductive n-type MOF has high crystalline quality with a conductivity of ~ 9.4 S·m
, which is at least two orders of magnitude higher than that of conventional 1D MOFs. Its electrical band gap (E
) and exciton binding energy (E
) are approximately 0.49 eV and 0.3 eV, respectively. When utilized as electrode material in a supercapacitor, the DDA-Cu exhibits good charge storage capacity and cycle stability. Meanwhile, as thse active semiconductor layer, it successfully simulates the artificial visual perception system with excellent bending resistance and air stability as a MOF-based flexible optoelectronic synaptic case. The controllable preparation of high-quality 1D DDA-Cu MOF may enable new architectural designs and various applications in the future.
Intrinsic electrical and excitonic properties of monolayer transition‐metal dichalcogenides can be revealed on CYTOP fluoropolymer substrates with greatly suppressed unintentional doping and ...dielectric screening. Ambipolar transport behavior is observed in monolayer WS2 by applying solid‐state back gates. The excitonic properties of monolayer MoS2 and WS2 are determined by intricate interplays between the bandgap renormalization, Pauli blocking, and carrier screening against carrier doping.
We report the metal-catalyst-free synthesis of high-quality polycrystalline graphene on dielectric substrates silicon dioxide (SiO2) or quartz using an oxygen-aided chemical vapor deposition (CVD) ...process. The growth was carried out using a CVD system at atmospheric pressure. After high-temperature activation of the growth substrates in air, high-quality polycrystalline graphene is subsequently grown on SiO2 by utilizing the oxygen-based nucleation sites. The growth mechanism is analogous to that of growth for single-walled carbon nanotubes. Graphene-modified SiO2 substrates can be directly used in transparent conducting films and field-effect devices. The carrier mobilities are about 531 cm2 V–1 s–1 in air and 472 cm2 V–1 s–1 in N2, which are close to that of metal-catalyzed polycrystalline graphene. The method avoids the need for either a metal catalyst or a complicated and skilled postgrowth transfer process and is compatible with current silicon processing techniques.
Covalent organic frameworks (COFs) can exhibit high specific surface area and catalytic activity, but traditional solution-based synthesis methods often lead to insoluble and infusible powders or ...fragile films on solution surface. Herein we report large-area -C=N- linked two-dimensional (2D) COF films with controllable thicknesses via vapor induced conversion in a chemical vapor deposition (CVD) system. The assembly process is achieved by reversible Schiff base polycondensation between PyTTA film and TPA vapor, which results in a uniform organic framework film directly on growth substrate, and is driven by π-π stacking interactions with the aid of water and acetic acid. Wafer-scale 2D COF films with different structures have been successfully synthesized by adjusting their building blocks, suggesting its generic applicability. The carrier mobility of PyTTA-TPA COF films can reach 1.89 × 10
cm
V
s
. When employed as catalysts in hydrogen evolution reaction (HER), they show high electrocatalytic activity compared with metal-free COFs or even some metallic catalysts. Our results represent a versatile route for the direct construction of large-area uniform 2D COF films on substrates towards multi-functional applications of 2D π-conjugated systems.
We report the fast growth of high-quality millimeter-size monolayer MoSe2 crystals on molten glass using an ambient pressure CVD system. We found that the isotropic surface of molten glass suppresses ...nucleation events and greatly improves the growth of large crystalline domains. Triangular monolayer MoSe2 crystals with sizes reaching ∼2.5 mm, and with a room-temperature carrier mobility up to ∼95 cm2/(V·s), can be synthesized in 5 min. The method can also be used to synthesize millimeter-size monolayer MoS2 crystals. Our results demonstrate that “liquid-state” glass is a highly promising substrate for the low-cost growth of high-quality large-size 2D transition metal dichalcogenides (TMDs).
Two-dimensional (2-D) polymer has properties that are attractive for energy storage applications because of its combination of heteroatoms, porosities and layered structure, which provides redox ...chemistry and ion diffusion routes through the 2-D planes and 1-D channels. Here, conjugated aromatic polymers (CAPs) were synthesized in quantitative yield via solid-state polymerization of phenazine-based precursor crystals. By choosing flat molecules (2-TBTBP and 3-TBQP) with different positions of bromine substituents on a phenazine-derived scaffold, C–C cross coupling was induced following thermal debromination. CAP-2 is polymerized from monomers that have been prepacked into layered structure (3-TBQP). It can be mechanically exfoliated into micrometer-sized ultrathin sheets that show sharp Raman peaks which reflect conformational ordering. CAP-2 has a dominant pore size of ∼0.8 nm; when applied as an asymmetric supercapacitor, it delivers a specific capacitance of 233 F g–1 at a current density of 1.0 A g–1, and shows outstanding cycle performance.
The ability to dope graphene is highly important for modulating electrical properties of graphene. However, the current route for the synthesis of N-doped graphene by chemical vapor deposition (CVD) ...method mainly involves high growth temperature using ammonia gas or solid reagent melamine as nitrogen sources, leading to graphene with low doping level, polycrystalline nature, high defect density and low carrier mobility. Here, we demonstrate a self-assembly approach that allows the synthesis of single-layer, single crystal and highly nitrogen-doped graphene domain arrays by self-organization of pyridine molecules on Cu surface at temperature as low as 300 °C. These N-doped graphene domains have a dominated geometric structure of tetragonal-shape, reflecting the single crystal nature confirmed by electron-diffraction measurements. The electrical measurements of these graphene domains showed their high carrier mobility, high doping level, and reliable N-doped behavior in both air and vacuum.
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