The electrocatalytic hydrogen evolution reaction (HER) has attracted increasing attention in the field of hydrogen-based economy, whereat developing cheap and efficient catalysts to reduce the use of Pt-based catalysts is highly required. Tin disulfide (SnS2) as a new rising star has exhibited intriguing properties in energy storage and conversion applications, while showing slow progress in HER due to the inherent poor activity. Herein, we demonstrate the successful structural engineering and simultaneous integration of trace amount Pt in SnS2 nanosheets via a facile and effective in situ cycling voltammetry activation process, leading to the efficiently synergistic HER. Defect-rich SnS2 nanosheets decorated with a trace amount (0.37 wt %) of Pt exhibit greatly enhanced HER activity due to the synergy between them, revealing low onset potential of 32 mV and overpotential of 117 mV at 10 mA/cm2, small Tafel slope of 69 mV/dec, and large exchange current density of 394.46 μA/cm2. Present work provides an intriguing strategy for developing ultralow loading Pt electrocatalysts with high HER performance.Keywords: defects-rich; layered metal dichalcogenides; Pt; SnS2 nanosheets; synergistic hydrogen evolution;

This study presents the successful growth of defective 2D terrace MoSe2/CoMoSe lateral heterostructures (LH), bilayer and multilayer MoSe2/CoMoSe LH, and vertical heterostructures (VH) nanolayers by doping metal cobalt (Co) element into MoSe2 atomic layers to form a CoMoSe alloy at high temperatures (∼900 °C). After the successful introduction of metal Co heterogeneity in the MoSe2 thin layers, more active sites can be created to enhance hydrogen evolution reaction (HER) activities combining with metal Co catalysis through mechanisms such as (1) atomic arrangement distortion in CoMoSe alloy nanolayers, (2) atomic level coarsening in LH interfaces and terrace edge layer architecture in VH, and (3) formation of defective 2D terrace MoSe2 nanolayers heterogeneous catalyst via metal Co doping. The HER investigations indicated that the obtained products with LH and VH exhibited an improved HER activity in comparison with those from pristine 2D MoSe2 electrocatalyst and LH type MoSe2/CoMoSe. The present work shows a facile yet reliable route to introduce metal ions into ultrathin 2D transition metal dichalcogenides (TMDCS) and produce defective 2D alloy atomic layers for exposing active sites, eventually improving their electrocatalytic performance.

The development trend of modern electronics and optoelectronics is towards continuous high integration and miniaturization. Using vertical configurations with three-dimensional geometry, it is easy to establish a higher integration density than the traditional planar one, and thus, this technology shows great promise for designing the next-generation electronics/optoelectronic devices. Two-dimensional (2D) layered metal dichalcogenides (2D-LMDs) are important building blocks for electronic/optoelectronic devices, where they are usually grown in parallel to the substrates during chemical vapor deposition (CVD), and consequently they are solely exploited to fabricate lateral structure devices with planar geometry. In this research, for the first time the vertical growth of free standing 2D layered nanosheets of hexagonal tin disulfide (SnS2) on a flat substrate was realized using a modified CVD method. Furthermore, it was successfully demonstrated, at the first attempt, that a type of non-planar vertical photodetector could be fabricated using free standing SnS2 nanosheets and this detector showed promise for photodetection applications. This work prepares the way for the growth of monodisperse vertical 2D-LMD nanosheets on flat substrates, and expands their use from conventional lateral structure devices to non-planar vertical electronic/optoelectronic devices.

Growth control over the size and shape of two-dimensional hexagonal boron nitride domains is vital for its applications. Here we develop a rational water-assisted chemical vapor deposition method that allows fast growth of large-sized (more than 330 μm) single crystal domains, which are 3–5 times larger than those previously grown on solid Cu or Cu–Ni alloy. Further kinetic control results in the perfect evolution of the domain shape from negatively curved triangle, triangle, positively curved triangle, regular hexagon, polygon, to circle. This work addresses the existing major problems, paving a way for the synthesis of materials with better control.

Two-dimensional (2D) metal dichalcogenides have emerged as attractive materials for application in photoelectrochemical (PEC) water splitting due to their unique structure and strong interaction with light. To date, deposition of exfoliated 2D nanosheet dispersions onto conductive substrates by a variety of techniques (e.g. casting, spin-coating and self-assembly) has been the most exploited approach to fabricate photoelectrodes from these materials. However, such solution processing strategies do not allow for control over the flake orientation and formation of intimate electrical contacts with conductive substrates. This could negatively affect the PEC efficiency. Herein, we demonstrate, for the first time, vertically aligned 2D SnS2 nanosheets with controllable growth and density on conductive substrates (FTO and carbon cloth (CC)) by a modified chemical vapor deposition (CVD) method. In PEC measurements, these vertically aligned 2D SnS2 nanosheet photoelectrodes exhibit a high incident photon to current conversion efficiency (IPCE) of up to 40.57% for SnS2⊥CC and 36.76% for SnS2⊥FTO at 360 nm, and a high photocurrent density of up to 1.92 ± 0.01 mA cm−2 for SnS2⊥CC and 1.73 ± 0.01 mA cm−2 for SnS2⊥FTO at 1.4 V vs. reversible hydrogen electrode (RHE). These values are two times higher than that of their photoelectrode (SnS2//FTO) counterparts prepared by conventional spin-coating. Our demonstration of this controllable growth strategy offers a versatile framework towards the design and fabrication of high performance PEC photoelectrodes based on 2D metal chalcogenides.

Considering the unique layered structure and novel optoelectronic properties of individual MoS2 and MoSe2, as well as the quantum coherence or donor–acceptor coupling effects between these two components, rational design and artificial growth of in-plane mosaic MoS2/MoSe2 lateral heterojunctions film on conventional amorphous SiO2/Si substrate are in high demand. In this article, large-area, uniform, high-quality mosaic MoS2/MoSe2 lateral heterojunctions film was successfully grown on SiO2/Si substrate for the first time by chemical vapor deposition (CVD) technique. MoSe2 film was grown along MoS2 triangle edges and occupied the blanks of the substrate, finally leading to the formation of mosaic MoS2/MoSe2 lateral heterojunctions film. The composition and microstructure of mosaic MoS2/MoSe2 lateral heterojunctions film were characterized by various analytic techniques. Photodetectors based on mosaic MoS2/MoSe2 lateral heterojunctions film, triangular MoS2 monolayer, and multilayer MoSe2 film are systematically investigated. The mosaic MoS2/MoSe2 lateral heterojunctions film photodetector exhibited optimal photoresponse performance, giving rise to responsivity, detectivity, and external quantum efficiency (EQE) up to 1.3 A W–1, 2.6 × 1011 Jones, and 263.1%, respectively, under the bias voltage of 5 V with 0.29 mW cm–2 (610 nm), possibly due to the matched band alignment of MoS2 and MoSe2 and strong donor–acceptor delocalization effect between them. Taking into account the similar edge conditions of transition metal dichalcogenides (TMDCs), such a facile and reliable approach might open up a unique route for preparing other 2D mosaic lateral heterojunctions films in a manipulative manner. Furthermore, the mosaic lateral heterojunctions film like MoS2/MoSe2 in the present work will be a promising candidate for optoelectronic fields.Keywords: 2D material; lateral heterostructure; MoS2/MoSe2; mosaic; photodetector;

•A novel Ta4+ doped Ta2O5 nanorod was prepared by facile vapor hydrolysis method.•The self-doped Ta2O5 nanorod displayed excellent visible light absorption and efficient visible-light photocatalytic activity for hydrogen production.•The formation of Ta4+ species effectively narrowed the band gap of Ta2O5.•Possible visible-light photocatalysis mechanism of the self-doped Ta2O5 nanorod for hydrogen production was proposed.Visible-light photocatalysis of the typical wide band gap semiconductor was often thought to be challenge and focus in the field of solar energy conversion. Hence, it was of great significance for wide band conductors to harvest visible light using photocatalysis technology. In this experiment, we successfully synthesized novel Ta4+ doped Ta2O5 nanorod by facile one-pot vapor hydrolysis method, and Ta4+ species was confirmed by XPS and EPR technology. The as-prepared Ta2O5 nanorod displayed amazing visible light absorption from 400 to 800 nm and visible light photocatalytic activity for hydrogen production, and the estimated band gap of Ta2O5-180, Ta2O5-200, Ta2O5-220 and Ta2O5-240 catalysts were about 2.93, 2.83, 2.75 and 2.53 eV, much lower than that of commercial Ta2O5 (3.88 eV). And the specific surface area of the self-doped Ta2O5 catalyst could reach up to 237.89 m2 g−1 with the typical mesoporous structure. It was noteworthy that the self-doped Ta2O5 nanorod displayed inspiring visible light photocatalytic activity for hydrogen production, which could reach up to 23.35 μmol g−1 h−1, while commercial Ta2O5 showed no visible light activity, mainly due to the formation of Ta4+ species in the as-prepared Ta2O5 nanorod. Besides, the self-doped Ta2O5 catalyst showed UV light photocatalytic activity of 10.17 × 103 μmol g−1 h−1 and the highly enhanced simulated sunlight photocatalytic activity of 356.68 μmol g−1 h−1 for hydrogen production, which were much higher than those of commercial Ta2O5. It was the formation of the Ta4+ species, high specific surface area, high crystallization and mesoporous structure that highly enhanced the UV light and simulated sunlight photocatalytic activity of the self-doped Ta2O5 nanorod. Finally, possible mechanism of the visible-light photocatalysis of the self-doped Ta2O5 nanorod for hydrogen production was also proposed in detail.Download high-res image (137KB)Download full-size image

Two-dimensional (2D) layered semiconductors have emerged as a highly attractive class of materials for flexible and wearable strain sensor-centric devices such as electronic-skin (e-skin). This is primarily due to their dimensionality, excellent mechanical flexibility, and unique electronic properties. However, the lack of effective and low-cost methods for wafer-scale fabrication of these materials for strain sensor arrays limits their potential for such applications. Here, we report growth of large-scale 2D In2Se3 nanosheets by templated chemical vapor deposition (CVD) method, using In2O3 and Se powders as precursors. The strain sensors fabricated from the as-grown 2D In2Se3 films show 2 orders of magnitude higher sensitivity (gauge factor ∼237 in −0.39% to 0.39% uniaxial strain range along the device channel length) than what has been demonstrated from conventional metal-based (gauge factor: ∼1–5) and graphene-based strain sensors (gauge factor: ∼2–4) in a similar uniaxial strain range. The integrated strain sensor array, fabricated from the template-grown 2D In2Se3 films, exhibits a high spatial resolution of ∼500 μm in strain distribution. Our results demonstrate the applicability and highly attractive properties of 2D layered semiconductors in e-skins for robotics and human body motion monitoring.

Backing materials play important role in enhancing the acoustic performance of an ultrasonic transducer. Most backing materials prepared by conventional methods failed to show both high acoustic impedance and attenuation, which however determine the bandwidth and axial resolution of acoustic transducer, respectively. In the present work, taking advantage of the structural feature of 3D graphene foam as a confined space for dense packing of tungsten spheres with the assistance of centrifugal force, the desired structural requirement for high impedance is obtained. Meanwhile, superior thermal conductivity of graphene contributes to the acoustic attenuation via the conversion of acoustic waves to thermal energy. The tight contact between tungstate spheres, epoxy matrix, or graphene makes the acoustic wave depleted easily for the absence of air barrier. The as-prepared 3DG/W80 wt %/epoxy film in 1 mm, prepared using ∼41 μm W spheres in diameter, not only displays acoustic impedance of 13.05 ± 0.11 MRayl but also illustrates acoustic attenuation of 110.15 ± 1.23 dB/cm MHz. Additionally, the composite film exhibits a high acoustic absorption coefficient, which is 94.4% at 1 MHz and 100% at 3 MHz, respectively. Present composite film outperforms most of the reported backing materials consisting of metal fillers/polymer blending in terms of the acoustic impedance and attenuation.

Organic dye molecules possessing modulated optical absorption bandwidth and molecular structures can be utilized as sensitizing species for the enhancement of photodetector performance of semiconductor via photoinduced charge transfer mechanism. MoS2 photodetector were modified by drop-casting of methyl orange (MO), rhodamine 6G (R6G), and methylene blue (MB) with different molecular structures and extinction coefficients, and enhanced photodetector performance in terms of photocurrent, photoresponsity, photodetectivity, and external quantum efficiency were obtained after modification of MO, R6G, and MB, respectively. Furthermore, dyes showed different modulating abilities for photodetector performance after combination with MoS2, mainly due to the variation of molecular structures and optical absorption bandwidth. Among tested dyes, deposition of MB onto monolayer MoS2 grown by CVD resulted in photocurrent ∼20 times as high as pristine MoS2 due to favorable photoinduced charge transfer of photoexcited electrons from flat MB molecules to the MoS2 layer. Meanwhile, the corresponding photoresponsivity, photodetectivity, and an external quantum efficiency are 9.09 A W1–, 2.2 × 1011 Jones, 1729% at 610 nm, respectively. Photoinduced electron-transfer measurements of the pristine MoS2 and dye-modified MoS2 indicated the n-doping effect of dye molecules on the MoS2. Additionally, surface-enhanced Raman measurements also confirmed the direct correlation with charge transfer between organic dyes and MoS2 taking into account the chemically enhanced Raman scattering mechanism. Present work provides a new clue for the manipulation of high-performance of two-dimensional layered semiconductor-based photodetector via the combination of organic dyes.Keywords: charge transfer; dye-sensitized; MoS2; n-doping; photodetector

The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2–SiC composites, the toughness of (2.0%) ZrB2–SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m1/2) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.Keywords: electrostatically assembled process; graphene; thermal shock resistance; toughness; zirconium diboride

Transition metal doped layered transition metal dichalcogenides (TMDs) are regarded as promising hydrogen evolution reaction (HER) candidates due to exposed active sites at both edges and basal planes. Hydrogen absorption free energy on active sites in doped materials are adjusted to thermoneutral state for ideal bond breaking to favour the HER process after the introduction of transition metal ions in their crystalline structures. Considering the importance of the active site, charge transfer, and hydrogen adsorption free energy to HER, cobalt-containing sandwich-type polyoxometalates are used as a precursor to fabricate cobalt doped WSe2 nanosheets via CVD selenization method. Reduced graphene oxides (rGO) are further introduced into cobalt doped WSe2 nanosheets for solving the non-ohmic contact with current collectors, leading to enhanced exchange current density. Co–WSe2/rGO2 composites exhibit Tafel slope of 64 mV dec−1, overpotential of 217 mV at 10 mA cm−2, exchange current density of 15.3 × 10−3 mA cm−2, charge transfer resistance of 68 Ω, and the activity is maintained after 3 h. The activated basal planes, good conductivity and adjusted hydrogen absorption free energy are attributed to enhance the HER performance. The present work opens a new avenue for the fabrication of transition metal doped TMDs using polyoxometalates with determined composition as precursors to fabricate superior HER electrocatalysts.

Phase engineering of two-dimensional (2D) materials offers unique opportunities for acquiring novel opto-electronic properties and allows for the searching of outstanding candidates for applications in opto-electronic detectors, sensors, catalysis, or phase-change memory devices. Here, we report the phase-transformation from β-InSe to γ-In2Se3, exploiting the thermal annealing route to trigger the process starting at 200 °C that expands the family of phase-change materials. The presence of γ-In2Se3 is solidly confirmed by the characteristic peaks in X-ray diffraction (XRD) and energy dispersive X-ray (EDX), and is quite stable at ambient condition, thus facilitating substantial application in phase-change memory devices. A Raman shift in the A′1 mode from 225 cm−1 to 230 cm−1 further illustrates the phase transformation. Besides the photoluminescence (PL) peak of β-InSe, the ∼2 eV PL peak, ascribed to γ-In2Se3, is observed in the annealed nanosheet. The increased PL band gap of β-InSe as a function of annealing temperature during phase transformation was possibly affected by the suppressed interlayer coupling, as well as the planar quantum confinement of photo-excited carriers by the external surfaces of the sheets. The photodetector performance with respect to photocurrent, mobility, detectivity, responsivity, and external quantum efficiency was subsequently evaluated after thermal annealing, showing deteriorated optical performance. The present work proved that thermal annealing could induce the successful phase transformation, and adjusted the opto-electronic properties in some extent, providing useful information for processing 2D materials based nano-devices.

Graphene on dielectric substrates is essential for its electronic applications. Graphene is typically synthesized on the surface of metal and then transferred to an appropriate substrate for fabricating device applications. This post growth transfer process is detrimental to the quality and performance of the as-grown graphene. Therefore, direct growth of graphene films on dielectric substrates without any transfer process is highly desirable. However, fast growth of graphene on dielectric substrates remains challenging. Here, we demonstrate a transfer-free chemical vapor deposition (CVD) method to directly grow graphene films on dielectric substrates at fast growth rate using Cu as floating catalyst. A large area (centimeter level) graphene can be grown within 15 min using this CVD method, which is increased by 500 times compared to other direct CVD growth on dielectric substrate in the literatures. This research presents a significant progress in transfer-free growth of graphene and graphene device applications.

Graphene-like layered semiconductors are a new class of materials for next generation electronic and optoelectronic devices due to their unique electrical and optical properties. A p–n junction is an elementary building block for electronics and optoelectronics devices. Here, we demonstrate the fabrication of a lateral p–n heterojunction diode of a thin-film InSe/CuInSe2 nanosheet by simple solid-state reaction. We discover that InSe nanosheets can be easily transformed into CuInSe2 thin film by reacting with elemental copper at a temperature of 300 °C. Photodetectors and photovoltaic devices based on this lateral heterojunction p–n diode show a large photoresponsivity of 4.2 A W–1 and a relatively high light-power conversion efficiency of 3.5%, respectively. This work is a giant step forward in practical applications of two-dimensional materials for next generation optoelectronic devices.

Highly stretchable and conductive core–sheath nanofibers are significant for flexible and wearable microelectronics. Core–sheath fibers were massively fabricated from ultralong chemical vapor deposition (CVD)-grown graphene bundles. They exhibited superior conductivity and excellent mechanical properties that exceeded those of the reduced graphene oxide fibers. The intrinsic dynamic fracture procedure and mechanism of the core–sheath nanofibers were investigated. Furthermore, safe strain sensors based on as-prepared core–sheath CVD graphene fibers have been demonstrated as a proof-of-concept application. The performance of strain sensors has been greatly improved by using CVD graphene fibers.

We demonstrate the strategies and principles for the performance improvement of layered semiconductor based photodetectors using multilayer indium selenide (InSe) as the model material. It is discovered that multiple reflection interference at the interfaces in the phototransistor device leads to a thickness-dependent photo-response, which provides a guideline to improve the performance of layered semiconductor based phototransistors. The responsivity and detectivity of InSe nanosheet phototransistor can be adjustable using applied gate voltage. Our InSe nanosheet phototransistor exhibits ultrahigh responsivity and detectivity. An ultrahigh external photo-responsivity of ∼104 A W−1 can be achieved from broad spectra ranging from UV to near infrared wavelength using our InSe nanosheet photodetectors. The detectivity of multilayer InSe devices is ∼1012 to 1013 Jones, which surpasses that of the currently exploited InGaAs photodetectors (1011 to 1012 Jones). This research shows that multilayer InSe nanosheets are promising materials for high performance photodetectors.

Novel switchable and tunable luminescent composite films consisting of Na9[EuW10O36]·32H2O (EuW10) and agarose have been prepared. EuW10 can be converted into a non-luminescent species by photoreduction and the recovery is facilitated by oxidation under moisture air. The luminescence recovery of the UV-reduced films showed dependence on the relative humidity (RH) ranging from 43 to 78% after a certain exposure time. X-ray photoelectron energy spectroscopy (XPS) measurements confirm the generation of the reduced W5+ species in EuW10 polyoxoanions. Further analysis of EuW10 indicates that the photo-generated d1 electron hopping is prohibited in the hybrid films. The absence of recombination of the photogenerated d1 electrons and holes, and the consumption of holes to form ˙OH radicals are responsible for the luminescence quenching rather than luminescence resonance energy transfer (LRET). The moisture-responsive behavior of the EuW10–agarose films is attributed to the kinetically controlled back reaction of W5+O6 with O2. The present study provides new insights into lanthanide-containing POMs as tunable luminescent components in UV and moisture dual-responsive materials.

A tungsten/epoxy composite film integrated with graphene oxide (GO) is prepared via a layer-by-layer assembly method, which shows enhanced acoustic attenuating performance compared with a tungsten/epoxy composite film in the absence of GO. The basic structure consists of tungsten/epoxy/GO/epoxy (W/E/GO/E), in which the inner wrapped epoxy acts as a buffer layer to anchor GO nanosheets on W spheres, and the outer wrapped epoxy layer is designed to prevent GO nanosheets peeling off from W spheres. The design was beneficial in guaranteeing the independence and integrity of the W/E/GO/E structure. The structure of the core–shell composites was characterized with Fourier-transform infrared spectra, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The acoustic properties of the films were evaluated by a conventional pulse-echo overlap technique at the frequency of 9 MHz. It was found that the acoustic attenuation of the optimal W/E/GO/E composite films was much higher than those of traditional W films at a band frequency range from 5 MHz to 12 MHz, and 36.58 ± 0.2 dB cm−1 MHz−1 was obtained at 9 MHz. The wrapping of GO on the surface of W/E will create a crumpled surface for better mixing with the epoxy matrix due to hydrogen bonding and chemical bonding, leading to the preparation of a high quality composite film with minimal structural defects including bubbles and cracks. The enhanced acoustic absorption property of the composite films was attributed to a synergistic effect among its multicomponents, as well as the contribution of GO's thermoacoustic effect. W/E/GO/E composite films with such excellent attenuation loss properties have promise to be the backing material for ultrasonic transducers.

The manipulation of the heat flow in a ceramic matrix composite is of great importance in industrial and academic fields. Energy flow, as a typical behavior of heat motion in ceramic surfaces can be confined within specific sites during thermal shock experiments, which weakens the temperature gradient distribution, and hence suppresses the crack propagation. The heat flow can be rationally controlled by the introduction of a nanostructured surface with a diverse forced convection coefficient and heat transfer resistance. Taking inspiration from a nanofin surface, yttria-stabilized zirconia (YSZ) nanostructures were fabricated using the sol–gel method. This bio-inspired coating exhibits a high forced convection coefficient (2.884 times) and high heat transfer resistance (30 times) because of the existence of irregular nanowires arrays and a porous nanostructure. The introduction of the nanostructured coating resulted in the rapid depression of the thermal gradient and stress concentration, and the crack propagation was also effectively suppressed. This sol–gel coating method effectively enhanced the thermal shock resistance of the ceramic materials, and indicates the potential for the application of ceramics in extreme environments.

Dipeptide-polyoxometalates (POMs)-graphene oxide (GO) ternary hybrid is an excellent peroxidase-like mimic, exhibiting enhanced peroxidase-like activity compared to POMs alone. The hybrid was readily prepared through a reprecipitation method involving electrostatic encapsulation of H3PW12O40 (PW12) by cationic diphenylalanine (FF) peptide and coassembly of FF@PW12 spheres with graphene oxide (GO). Using 3,3′,5,5′-tetramethylbenzidine (TMB) as the chromogenic substrate, the peroxidase-like activity of FF@PW12 was evaluated in the heterogeneous phase, and it is 13 times higher than that of pristine PW12 in the homogeneous phase. Furthermore, ternary hybrids of FF@PW12@GO containing 5 wt % GO could enhance the activity 1.7 times higher than that of FF@PW12. The noncovalent interactions of hydrogen bonding and ionic interaction between GO and POMs are speculated to result in the synergistic effect for the enhancement of peroxidase-like performance. The strong interactions between rGO and PW12 are evaluated by a four-probe Hall measurement via the van der Pauw method, and rGO is significantly p-doped by the doping effect of PW12 with lower LUMO energy than that of the energy level of rGO and also due to the electron reservoir feature of PW12. Cyclic voltammogram measurements also suggest that GO causes significant influence on the electronic structure of the reduced forms of the redox couples of PW12. The nature of the TMB catalytic reaction may originate from the generation of the hydroxyl radical (•OH) from the decomposition of H2O2 by ternary hybrids and the formation of peroxo species of POM. Taking advantage of the UV–vis signals of TMB being correlated to the concentration of H2O2, FF@PW12@GO can be used to detect H2O2 within the limit of detection of 0.11 μM, and the detection range is 1–75 μM. The present method indeed opens up a promising route in constructing heterogeneous peroxidase-like mimics through the use of POMs via the introduction of GO for building H2O2 sensors.Keywords: diphenylalanine; graphene; peroxidase-like; polyoxometalates; synergistic effect

We report a modulation of threshold voltage instability of back-gated multilayer InSe FETs by gate bias stress. The performance stability of multilayer InSe FETs is affected by gate bias polar, gate bias stress time and gate bias sweep rate under ambient conditions. The on-current increases and threshold voltage shifts to negative gate bias stress direction with negative bias stress applied, which are opposite to that of positive bias stress. The intensity of gate bias stress effect is influenced by applied gate bias time and the sweep rate of gate bias stress. The behavior can be explained by the surface charge trapping model due to the adsorbing/desorbing oxygen and/or water molecules on the InSe surface. This study offers an opportunity to understand gate bias stress modulation of performance instability of back-gated multilayer InSe FETs and provides a clue for designing desirable InSe nanoelectronic and optoelectronic devices.Keywords: field-effect transistors; indium selenide; multilayer; threshold voltage instability

Transparency in the infrared (IR) light region and high conductivity for electromagnetic (EM) shielding performance are contradicting properties for conventional window materials. It is challenging to explore a new class of materials with both IR transmittance and high electrical conductivity. Herein, middle-IR transmittance and EM-shielding performance are realized by graphene network fabrics (GNFs). GNFs are fabricated by chemical vapor deposition using copper mesh with different geometric constructions as the sacrificial substrate. The structure of GNFs endows the as-fabricated material high IR transmittance, good electrical conductivity, and EM-shielding efficiency. The grid parameter τ with regard to the square aperture and wire width exerts a profound effect on the EM-shielding performance. The highest EM-shielding efficiency is 12.86 dB at 10 GHz with a transmittance of 70.85% at 4500 nm. Meanwhile, the highest IR light transmittance is 87.85% with an EM-shielding efficiency of 4 dB. Based on the experimental and theoretical analyses, the EM-shielding efficiency is prominently dependent on microwave absorption.

This work is focused on achieving high performance multilayer InSe field-effect transistors by a systematic experiment study on metal contacts. The high performance can be achieved by choosing an ideal contact metal and adopting a proper thickness of InSe nanosheets. By choosing a proper thickness (33 nm), the performance of multilayer InSe FETs was improved by the following sequence of Al, Ti, Cr and In contacts. The extracted mobility values are 4.7 cm2 V−1 s−1, 27.6 cm2 V−1 s−1, 74 cm2 V−1 s−1 and 162 cm2 V−1 s−1 for Al, Ti, Cr and In, respectively. The on/off ratios are 107–108. The device electronic properties and the interface morphology of the deposition metals/InSe indicate that the contact interface between the metals and InSe plays a significant role in forming low resistance. Our study may pave the way for multilayer InSe applications in nano-electrical and nano-optoelectronic devices.

A hybrid nanomaterial of Co/Cu2O based on carbon nanotubes (CNTs) is proposed as a highly promising photocatalyst for solar hydrogen production. Cu2O nanoparticles are active catalysts for hydrogen evolution from copper acetate by polyol process, but Cu0 nanoparticles are easily formed in this process, resulting in Cu associated Cu2O. To suppress the formation of metallic copper, metallic cobalt loaded CNT is used as a substitute for the non-loaded CNT for Cu2O formation. The metallic cobalt nanoparticles are not only effective in preventing the reduction of Cu2+ to Cu0, but they also enhance the efficiency of the CNT-substrated hybrid material preparation. Furthermore, graphene oxide (GO) is formed in the fabrication process of CNT/Co materials, and the GO is obtained from the exfoliated tube wall of CNT, which is evidenced by the uneven distribution of Co and Co/Cu2O on the GO flakes. The hybrid materials of CNT/Co/Cu2O and [CNT + GO]/Co/Cu2O are investigated as photocatalysts for water splitting. The results reveal that CNT/Co/Cu2O and [CNT + GO]/Co/Cu2O can be used to split water, thus enabling the economic production of hydrogen.

We report the eco-friendly chitosan assisted synthesis of 3D graphene@chitosan@Au nanosheet (3DG@CS@AuNSs) composites without using any toxic reductants or capping agents. The 3D graphene network consists of few-layer graphene sheets. One the one hand, the interfacial energy between graphene and Au nanostructures is significantly weakened due to the existence of chitosan polymers, serving as “glue” for anchoring Au nanosheets on the surface of 3D graphene. On the other hand, chitosan contains abundant hydroxyl and amine groups acting as reducing and stabilizing agents for the formation and even distribution of Au nanosheets. Mild redox reaction between hydrochloroauric ions and hydroxyl and amine groups occurred under thermal conditions due to the matching electrochemical potentials of the oxidants and reductants. The as-prepared 3DG@AuNSs exhibited much higher activities than that of 3DG@Au nanoaggregates towards the reduction of 4-nitrophenol, as well as more convenient recyclability than other supported Au NPs in terms of a robust free-standing foam structure. Furthermore, high performance liquid chromatography was also applied to monitor the emergence of 4-aminophenol during reaction. The present studies not only build a new route for the design of a robust and free-standing foam catalyst based on the integration of graphene and Au nanostructures by the assistance of a natural polymer, but also shed deep insight on the understanding of the synergistic catalytic activity towards nitrophenols.

Large-area heteroatom-doped graphene films are greatly attractive materials for various applications, such as electronics, fuel cells, and supercapacitors. Currently, these graphene films are prepared by the high-temperature chemical vapor deposition method, which produces a low doping level in N-doped graphene (NG) and fails in the synthesis of large-area S-doped graphene (SG) film. Here, we report a low-temperature method toward the synthesis of large-area heavily heteroatom-doped graphene on copper foils via a free radical reaction using polyhalogenated aromatic compounds. This low-temperature method allows the synthesis of single-layer NG film with a high nitrogen content, and the production of large-area SG film for the first time. Both doped graphenes show enhanced electrical properties in field effect transistors as well as high-performance electrocatalysts for fuel cells.

We report the facile synthesis of environmentally benign Au NPs/chitosan composites and magnetic Au NPs/chitosan/Fe3O4 composites without employing any toxic reductants or capping agents. Renewable natural chitosan not only functioned as supporting matrix, but also served as a reductant and stabilizer for the formation and dispersions of Au NPs. Fe3O4 nanospheres were easily embedded into the chitosan matrix due to the strong complexation ability of chitosan with Fe3O4, which originated from the sharing of the lone electron pairs from the nitrogen atom in amine with FeII or FeIII on the surface of Fe3O4. The as-prepared magnetic composites exhibited much higher activities, as well as more convenient magnetic recyclability than other supported Au NPs towards the reduction of 4-nitrophenol. From the practical point of view, apart from good performance of the reduction of nitro compounds, the biocompatibility and biodegradability of present Au NPs/chitosan/Fe3O4 composites promote the potential applications in the biochemical catalysis or therapy.

Two-dimensional (2D) semiconductors are limited to graphene analogues of layered materials, so it is extremely challenging to fabricate 2D non-layered materials with thicknesses of only a few atomic layers. Here, we report the successful fabrication of 2D Ga2O3 from the corresponding GaSe nanosheets and a solar blind photodetector based on 2D Ga2O3. The as-prepared 2D β-Ga2O3 is polycrystalline and has a thickness of less than 10 nm. Furthermore, we demonstrate a photodetector based on 2D β-Ga2O3, which show a sensitive, fast and stable photoresponse to ultraviolet radiation (254 nm). The responsivity, detectivity and external quantum efficiency of the photodetector are 3.3 A W−1, 4.0 × 1012 Jones and 1600%, respectively, indicating that the 2D Ga2O3 has great potential for application for solar-blind photodetectors.

CuGaSe2 is an important non-layered I–III–VI2 compound with superior optical properties. In this work, monocrystal two-dimensional (2D) CuGaSe2 nanosheets were successfully synthesized via a simple solid-state reaction. The electronic and optoelectronic properties of photodetectors based on 2D CuGaSe2 nanosheets were investigated for the first time. 2D CuGaSe2 FETs present a typical p-type conductance behaviour, and photodetectors based on 2D CuGaSe2 show a sensitive response to the UV-visible spectrum. Under 490 nm light illumination, the responsivity and detectivity of photodetectors are as high as 103 AW−1 and 8 × 1011 Jones, respectively. Our results offer a new opportunity to use 2D CuGaSe2 nanosheets for future nano-optoelectronic devices.

Highly sensitive phototransistors based on two-dimensional (2D) GaTe nanosheet have been demonstrated. The performance (photoresponsivity, detectivity) of the GaTe nanosheet phototransistor can be efficiently adjusted by using the applied gate voltage. The devices exhibit an ultrahigh photoresponsivity of 274.3 AW−1. The detectivity of 2D GaTe devices is ∼1012 Jones, which surpasses that of currently-exploited InGaAs photodetectors (1011−1012 Jones). To reveal the origin of the enhanced photocurrent in GaTe nanosheets, theoretical modeling of the electronic structures was performed to show that GaTe nanosheets also have a direct bandgap structure, which contributes to the promotion of photon absorption and generation of excitons. This work shows that GaTe nanosheets are promising materials for high performance photodetectors.

The first GaS nanosheet-based photodetectors are demonstrated on both mechanically rigid and flexible substrates. Highly crystalline, exfoliated GaS nanosheets are promising for optoelectronics due to strong absorption in the UV–visible wavelength region. Photocurrent measurements of GaS nanosheet photodetectors made on SiO2/Si substrates and flexible polyethylene terephthalate (PET) substrates exhibit a photoresponsivity at 254 nm up to 4.2 AW–1 and 19.2 AW–1, respectively, which exceeds that of graphene, MoS2, or other 2D material-based devices. Additionally, the linear dynamic range of the devices on SiO2/Si and PET substrates are 97.7 dB and 78.73 dB, respectively. Both surpass that of currently exploited InGaAs photodetectors (66 dB). Theoretical modeling of the electronic structures indicates that the reduction of the effective mass at the valence band maximum (VBM) with decreasing sheet thickness enhances the carrier mobility of the GaS nanosheets, contributing to the high photocurrents. Double-peak VBMs are theoretically predicted for ultrathin GaS nanosheets (thickness less than five monolayers), which is found to promote photon absorption. These theoretical and experimental results show that GaS nanosheets are promising materials for high-performance photodetectors on both conventional silicon and flexible substrates.

PDMS based imprinting is firstly developed for patterning of rGO on a large area. High quality stripe and square shaped rGO patterns are obtained and the electrical properties of the rGO film can be adjusted by the concentration of GO suspension. The arrays of rGO electronics are fabricated from the patterned film by a simple shadow mask method. Gas sensors, which are based on these rGO electronics, show high sensitivity and recyclable usage in sensing NH3.

This study has been performed on the synthesis of a large area, uniform graphene film on tilted copper foil against gaseous flow in a chemical vapor deposition (CVD) system. The copper foil on which the graphene grows is tilted against gaseous flow in the CVD process, which promotes the uniformity of graphene due to geometrical fluidic dynamics. The uniform graphene film with grain size up to ten micrometers and few defects has been synthesized on copper foils using optimized parameters including growth time, methane concentration and growth temperature. Field effect transistors made of the grown graphene show high carrier mobilities of 5080.5 cm2 V−1 s−1, indicating fine quality graphene. These uniform graphenes can be used as high performance, flexible transparent conductors, which show improved tradeoff between conductivity and transparency: the transmittance of 96.5% at 550 nm with sheet resistance of ∼600 Ω sq−1, and the transmittance of 86.7% at 550 nm with sheet resistance of ∼400 Ω sq−1.

Two-dimensional (2D) semiconductor nanomaterials hold great promises for future electronics and optics. In this paper, a 2D nanosheets of ultrathin GaSe has been prepared by using mechanical cleavage and solvent exfoliation method. Single- and few-layer GaSe nanosheets are exfoliated on an SiO2/Si substrate and characterized by atomic force microscopy and Raman spectroscopy. Ultrathin GaSe-based photodetector shows a fast response of 0.02 s, high responsivity of 2.8 AW–1 and high external quantum efficiency of 1367% at 254 nm, indicating that the two-dimensional nanostructure of GaSe is a new promising material for high performance photodetectors.Keywords: gallium selenide; nanosheets; photodetectors

Patterned graphene with sub–microscale resolution is urgently required in its band–engineering and electronics applications. Several methods, such as conventional lithography, unzipping carbon nanotubes, chemical synthesis, assembling, shadow mask etching, have been proposed and demonstrated. Despite these advantages, an increasing demand for rapid, massively, high–throughput, and low–cost fabrication strategies for graphene ribbons continues to motivate research. Herein, we present an innovative approach for fabrication of graphene ribbon array by combining the soft–lithography with oxygen plasma etching. Large–scale, high–quality chemical vapor deposition graphene film was patterned into aligned ribbons with width in the range of several hundred nanometers to tens of micrometers (e.g., 100 nm∼30 μm) and periods, according to the size of PDMS stamp and etching time. The morphology and quality of patterned graphene ribbons were characterized using optical microscopy, scanning electron microscopy and Raman spectroscopy. Electrical measurements on patterned graphene ribbons show a symmetric transport behavior, which could be an ideal platform for sensing. Further, temperature dependent conductance measurements reveal a thermal excitation effect. Our strategies open a new avenue to patterned graphene ribbons for multi–functional nanodevice engineering.

We demonstrate the strategies and principles for the performance improvement of layered semiconductor based photodetectors using multilayer indium selenide (InSe) as the model material. It is discovered that multiple reflection interference at the interfaces in the phototransistor device leads to a thickness-dependent photo-response, which provides a guideline to improve the performance of layered semiconductor based phototransistors. The responsivity and detectivity of InSe nanosheet phototransistor can be adjustable using applied gate voltage. Our InSe nanosheet phototransistor exhibits ultrahigh responsivity and detectivity. An ultrahigh external photo-responsivity of ∼104 A W−1 can be achieved from broad spectra ranging from UV to near infrared wavelength using our InSe nanosheet photodetectors. The detectivity of multilayer InSe devices is ∼1012 to 1013 Jones, which surpasses that of the currently exploited InGaAs photodetectors (1011 to 1012 Jones). This research shows that multilayer InSe nanosheets are promising materials for high performance photodetectors.

We report the facile synthesis of environmentally benign Au NPs/chitosan composites and magnetic Au NPs/chitosan/Fe3O4 composites without employing any toxic reductants or capping agents. Renewable natural chitosan not only functioned as supporting matrix, but also served as a reductant and stabilizer for the formation and dispersions of Au NPs. Fe3O4 nanospheres were easily embedded into the chitosan matrix due to the strong complexation ability of chitosan with Fe3O4, which originated from the sharing of the lone electron pairs from the nitrogen atom in amine with FeII or FeIII on the surface of Fe3O4. The as-prepared magnetic composites exhibited much higher activities, as well as more convenient magnetic recyclability than other supported Au NPs towards the reduction of 4-nitrophenol. From the practical point of view, apart from good performance of the reduction of nitro compounds, the biocompatibility and biodegradability of present Au NPs/chitosan/Fe3O4 composites promote the potential applications in the biochemical catalysis or therapy.

Two-dimensional (2D) metal dichalcogenides have emerged as attractive materials for application in photoelectrochemical (PEC) water splitting due to their unique structure and strong interaction with light. To date, deposition of exfoliated 2D nanosheet dispersions onto conductive substrates by a variety of techniques (e.g. casting, spin-coating and self-assembly) has been the most exploited approach to fabricate photoelectrodes from these materials. However, such solution processing strategies do not allow for control over the flake orientation and formation of intimate electrical contacts with conductive substrates. This could negatively affect the PEC efficiency. Herein, we demonstrate, for the first time, vertically aligned 2D SnS2 nanosheets with controllable growth and density on conductive substrates (FTO and carbon cloth (CC)) by a modified chemical vapor deposition (CVD) method. In PEC measurements, these vertically aligned 2D SnS2 nanosheet photoelectrodes exhibit a high incident photon to current conversion efficiency (IPCE) of up to 40.57% for SnS2⊥CC and 36.76% for SnS2⊥FTO at 360 nm, and a high photocurrent density of up to 1.92 ± 0.01 mA cm−2 for SnS2⊥CC and 1.73 ± 0.01 mA cm−2 for SnS2⊥FTO at 1.4 V vs. reversible hydrogen electrode (RHE). These values are two times higher than that of their photoelectrode (SnS2//FTO) counterparts prepared by conventional spin-coating. Our demonstration of this controllable growth strategy offers a versatile framework towards the design and fabrication of high performance PEC photoelectrodes based on 2D metal chalcogenides.

The manipulation of the heat flow in a ceramic matrix composite is of great importance in industrial and academic fields. Energy flow, as a typical behavior of heat motion in ceramic surfaces can be confined within specific sites during thermal shock experiments, which weakens the temperature gradient distribution, and hence suppresses the crack propagation. The heat flow can be rationally controlled by the introduction of a nanostructured surface with a diverse forced convection coefficient and heat transfer resistance. Taking inspiration from a nanofin surface, yttria-stabilized zirconia (YSZ) nanostructures were fabricated using the sol–gel method. This bio-inspired coating exhibits a high forced convection coefficient (2.884 times) and high heat transfer resistance (30 times) because of the existence of irregular nanowires arrays and a porous nanostructure. The introduction of the nanostructured coating resulted in the rapid depression of the thermal gradient and stress concentration, and the crack propagation was also effectively suppressed. This sol–gel coating method effectively enhanced the thermal shock resistance of the ceramic materials, and indicates the potential for the application of ceramics in extreme environments.

CuGaSe2 is an important non-layered I–III–VI2 compound with superior optical properties. In this work, monocrystal two-dimensional (2D) CuGaSe2 nanosheets were successfully synthesized via a simple solid-state reaction. The electronic and optoelectronic properties of photodetectors based on 2D CuGaSe2 nanosheets were investigated for the first time. 2D CuGaSe2 FETs present a typical p-type conductance behaviour, and photodetectors based on 2D CuGaSe2 show a sensitive response to the UV-visible spectrum. Under 490 nm light illumination, the responsivity and detectivity of photodetectors are as high as 103 AW−1 and 8 × 1011 Jones, respectively. Our results offer a new opportunity to use 2D CuGaSe2 nanosheets for future nano-optoelectronic devices.

PDMS based imprinting is firstly developed for patterning of rGO on a large area. High quality stripe and square shaped rGO patterns are obtained and the electrical properties of the rGO film can be adjusted by the concentration of GO suspension. The arrays of rGO electronics are fabricated from the patterned film by a simple shadow mask method. Gas sensors, which are based on these rGO electronics, show high sensitivity and recyclable usage in sensing NH3.

A tungsten/epoxy composite film integrated with graphene oxide (GO) is prepared via a layer-by-layer assembly method, which shows enhanced acoustic attenuating performance compared with a tungsten/epoxy composite film in the absence of GO. The basic structure consists of tungsten/epoxy/GO/epoxy (W/E/GO/E), in which the inner wrapped epoxy acts as a buffer layer to anchor GO nanosheets on W spheres, and the outer wrapped epoxy layer is designed to prevent GO nanosheets peeling off from W spheres. The design was beneficial in guaranteeing the independence and integrity of the W/E/GO/E structure. The structure of the core–shell composites was characterized with Fourier-transform infrared spectra, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The acoustic properties of the films were evaluated by a conventional pulse-echo overlap technique at the frequency of 9 MHz. It was found that the acoustic attenuation of the optimal W/E/GO/E composite films was much higher than those of traditional W films at a band frequency range from 5 MHz to 12 MHz, and 36.58 ± 0.2 dB cm−1 MHz−1 was obtained at 9 MHz. The wrapping of GO on the surface of W/E will create a crumpled surface for better mixing with the epoxy matrix due to hydrogen bonding and chemical bonding, leading to the preparation of a high quality composite film with minimal structural defects including bubbles and cracks. The enhanced acoustic absorption property of the composite films was attributed to a synergistic effect among its multicomponents, as well as the contribution of GO's thermoacoustic effect. W/E/GO/E composite films with such excellent attenuation loss properties have promise to be the backing material for ultrasonic transducers.

Two-dimensional (2D) semiconductors are limited to graphene analogues of layered materials, so it is extremely challenging to fabricate 2D non-layered materials with thicknesses of only a few atomic layers. Here, we report the successful fabrication of 2D Ga2O3 from the corresponding GaSe nanosheets and a solar blind photodetector based on 2D Ga2O3. The as-prepared 2D β-Ga2O3 is polycrystalline and has a thickness of less than 10 nm. Furthermore, we demonstrate a photodetector based on 2D β-Ga2O3, which show a sensitive, fast and stable photoresponse to ultraviolet radiation (254 nm). The responsivity, detectivity and external quantum efficiency of the photodetector are 3.3 A W−1, 4.0 × 1012 Jones and 1600%, respectively, indicating that the 2D Ga2O3 has great potential for application for solar-blind photodetectors.

Novel switchable and tunable luminescent composite films consisting of Na9[EuW10O36]·32H2O (EuW10) and agarose have been prepared. EuW10 can be converted into a non-luminescent species by photoreduction and the recovery is facilitated by oxidation under moisture air. The luminescence recovery of the UV-reduced films showed dependence on the relative humidity (RH) ranging from 43 to 78% after a certain exposure time. X-ray photoelectron energy spectroscopy (XPS) measurements confirm the generation of the reduced W5+ species in EuW10 polyoxoanions. Further analysis of EuW10 indicates that the photo-generated d1 electron hopping is prohibited in the hybrid films. The absence of recombination of the photogenerated d1 electrons and holes, and the consumption of holes to form ˙OH radicals are responsible for the luminescence quenching rather than luminescence resonance energy transfer (LRET). The moisture-responsive behavior of the EuW10–agarose films is attributed to the kinetically controlled back reaction of W5+O6 with O2. The present study provides new insights into lanthanide-containing POMs as tunable luminescent components in UV and moisture dual-responsive materials.

Layered transition metal dichalcogenides (TMDs) are considered as promising hydrogen evolution reaction (HER) candidates due to their exposed active sites at edges and superior electron mobility along sheets, however their inert basal planes and non-ohmic contact with current collectors greatly hamper their application in HER reactions. Exposing active sites, accelerating charge transfer, and manipulating hydrogen adsorption free energy close to thermoneutral are significant to favor the HER process. Herein, component-controllable 3D MoS2(1−x)Se2x alloy nanosheets with a vertically oriented architecture were successfully grown on conductive carbon cloth substrates through a CVD technique. The bigger radius of Se can cause a slight distortion and bring about a polarized electric field in the basal planes, resulting in favorable bond breaking of adsorbed molecules. Among all tested catalysts, Mo(S0.53Se0.47)2 alloy nanosheets exhibit the lowest Tafel slope (55.5 mV dec−1), smallest overpotential (183 mV) at 10 mA cm−2, and highest conductivity. The Mo(S0.53Se0.47)2 alloy maintains its activity after 2000 cycles. Density functional theory calculations manifest adjustment of hydrogen adsorption free-energies and vacancy formation energies in MoS2(1−x)Se2x alloy nanosheets. S and Se vacancies serve as a crucial factor for HER performance. The 3D exposed active sites, adjusted hydrogen adsorption free energy, vacancy formation energies, and ohmic contact with carbon cloth are found to be responsible for the enhanced HER performance.

This work is focused on achieving high performance multilayer InSe field-effect transistors by a systematic experiment study on metal contacts. The high performance can be achieved by choosing an ideal contact metal and adopting a proper thickness of InSe nanosheets. By choosing a proper thickness (33 nm), the performance of multilayer InSe FETs was improved by the following sequence of Al, Ti, Cr and In contacts. The extracted mobility values are 4.7 cm2 V−1 s−1, 27.6 cm2 V−1 s−1, 74 cm2 V−1 s−1 and 162 cm2 V−1 s−1 for Al, Ti, Cr and In, respectively. The on/off ratios are 107–108. The device electronic properties and the interface morphology of the deposition metals/InSe indicate that the contact interface between the metals and InSe plays a significant role in forming low resistance. Our study may pave the way for multilayer InSe applications in nano-electrical and nano-optoelectronic devices.

This study presents the successful growth of defective 2D terrace MoSe2/CoMoSe lateral heterostructures (LH), bilayer and multilayer MoSe2/CoMoSe LH, and vertical heterostructures (VH) nanolayers by doping metal cobalt (Co) element into MoSe2 atomic layers to form a CoMoSe alloy at high temperatures (∼900 °C). After the successful introduction of metal Co heterogeneity in the MoSe2 thin layers, more active sites can be created to enhance hydrogen evolution reaction (HER) activities combining with metal Co catalysis through mechanisms such as (1) atomic arrangement distortion in CoMoSe alloy nanolayers, (2) atomic level coarsening in LH interfaces and terrace edge layer architecture in VH, and (3) formation of defective 2D terrace MoSe2 nanolayers heterogeneous catalyst via metal Co doping. The HER investigations indicated that the obtained products with LH and VH exhibited an improved HER activity in comparison with those from pristine 2D MoSe2 electrocatalyst and LH type MoSe2/CoMoSe. The present work shows a facile yet reliable route to introduce metal ions into ultrathin 2D transition metal dichalcogenides (TMDCS) and produce defective 2D alloy atomic layers for exposing active sites, eventually improving their electrocatalytic performance.