Ultrathin Heterostructure Research Articles

Bimetallic Fe/Ni-BTC MOF decorated MXene hybrid for improved oxidation of water

Electrochemical production of green hydrogen via water-splitting is an emerging technology to generate a substitute source of energy. However, due to the slow kinetics of oxygen evolution reaction (OER), high cost, lesser availability and easy oxidation of noble metal-based electrocatalysts led the explorers to find an efficient and low-cost electrocatalysts. In the current communication, we have developed a synthesis strategy for the preparation of hybrid electrocatalyst composed of bimetallic (iron, nickel) based metal organic framework (FeNiBTC MOF) and MXene (Ti3C2Tx) via solvothermal reaction. Thanks to the ultrathin heterostructure with high electrical conductivity of MXene, with abundant active sites of FeNiBTC MOF, the as-prepared hybrid electrocatalyst FeNiBTC@MXene, leads the high efficiency OER in an alkaline environment. FeNiBTC MOF was impeccably decorated on the surfaces of MXene nanosheets with different FeNiBTC to MXene ratios and was characterized via pXRD, FESEM/EDS, XPS and BET. The optimized hybrid structured catalyst (FeNiBTC@Mx-3) revealed the best performance for OER with a low overpotential of 210 mV vs. RHE at a current density of 10 mA/cm2 and a Tafel plot value of 38.4 mV/dec and stable up to 1000th CV cycles.

Interface engineering of 2D NiFe LDH/NiFeS heterostructure for highly efficient 5-hydroxymethylfurfural electrooxidation

The electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to valuable chemicals is an efficient way to upgrade biomass molecules and replace traditional catalytic synthesis. It is crucial to develop efficient and low-cost earth-abundant electrocatalysts to enhance catalytic performance of HMF oxidation. Herein, a new type of two-dimensional (2D) hybrid arrays consisting of NiFe layered double hydroxides (LDH) nanosheets and bimetallic sulfide (NiFeS) is constructed via interface engineering for efficient electrocatalytic oxidation of HMF to 2,5-furandicarboxylic acid (FDCA). The preparation process of 2D NiFe LDH/NiFeS with ultrathin heterostructure involves in anchoring a Co-based metal-organic framework (Co MOF) as template onto the carbon cloth (CC) via in-situ growth, formation of NiFe LDH on the surface of Co MOF and subsequent partial sulfidation. The electrocatalyst of NiFe LDH/NiFeS exhibits outstanding performance towards HMF oxidation, about 98.5% yield for FDCA and 97.2% Faraday efficiency (FE) in the alkaline electrolyte with 10 mmol/L HMF, as well as excellent stability retaining 90.1% FE for FDCA after six cycles test. Moreover, even at an HMF concentration of 100 mmol/L, the yield and FE for FDCA remain high at 83.6% and 93.6%, respectively. These findings highlight that 2D heterostructure containing abundant interfaces between NiFe LDH nanosheets and NiFeS can enhance the intrinsic activity of LDH and thus promote the oxidation reaction kinetics. Additionally, the synergistic effect of the bimetallic NiFe compounds also improved the selectivity of HMF conversion to FDCA. Our present work demonstrates that constructing 2D ultrathin heterostructure of NiFe LDH/NiFeS is a facile strategy via interface engineering to enhance the intrinsic activity of LDH electrocatalysts, which would open new avenues toward low-cost and advanced 2D nanocatalysts for sustainable energy conversion and electrochemical valorization of biomass derivatives.

Facile construction of MoS2 decorated CdS hybrid heterojunction with enhanced hydrogen generation performance

Promoting the charge separation to improve photocatalytic performance of semiconductor photocatalysts is very important in the field of artificial photosynthesis. Here, a novel MoS2/CdS 2D–2D ultrathin nanosheet heterostructure was fabricated via a one-pot solvothermal route. The obtained 2D–2D MoS2/CdS nanojunction has not only provided large contact areas, but also shortened the charge transport distance, resulting in significantly enhanced photocatalytic H2 evolution property. The composites that were synthesized were examined using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Transmission electron microscope (TEM), UV-vis diffuse reflectance spectra (DRS), Photoluminescence (PL) and X-ray photoelectron spectra (XPS) analysis. By optimizing the 2D MoS2 amounts in the heterojunction, the 5 wt.% 2D/2D MoS2/CdS heterojunction displayed the maximal photocatalytic H2 evolution rate of 4449 μmolh−1g−1 under visible light irradiation in the presence of lactic acid as the sacrificial reagent, which was 6 times higher than that of pristine 2D CdS. Based on the photoelectrochemical and photoluminescence spectra tests, it could be deduced that the charge separation and transfer of 2D/2D MoS2/CdS heterojunction was tremendously improved, and the recombination of photoinduced electron-hole pairs was effectively impeded. Moreover, the 2D MoS2 was used as a cocatalyst to provide the abundant active sites and lower the overpotential for H2 generation reaction. The current work would offer an insight to fabricate the 2D/2D heterojunction photocatalysts for splitting H2O into H2.

Enhanced Ferromagnetism in Atomically Thin Oxides Achieved by Interfacial Reconstruction

AbstractDiscoveries of ferromagnetic materials with ultrathin thickness are of great importance for both fundamental science and technological applications. Transition metal oxides (TMOs) provide promising candidates in the context of next‐generation spintronics, despite the severe decay of ferromagnetism as the thickness reduces to the nanometer regime. Here, an efficient strategy to eliminate the magnetic dead layer in atomically thin oxides is presented, by using the epitaxial interface of 3d and 5d oxide monolayers that reconciles both strong exchange interaction and large uniaxial magnetic anisotropy. Combining multiple experimental methods, a ferromagnetic transition in an ultrathin oxide heterostructure comprised of only one La0.2Sr0.8MnO3 monolayer sandwiched by SrIrO3 monolayer (total thickness of three unit‐cells) is unambiguously demonstrated. Remarkably, a largely enhanced saturation magnetization (2 µB Mn−1) and Curie temperature (80 K) are observed for the single manganite monolayer, as compared to previously reported ferromagnetic monolayer oxides. The results demonstrate a general strategy for creating robust ferromagnetism in ultrathin TMOs, potentially enabling novel oxide spin‐orbitronic devices.

Mapping the intrinsic photocurrent streamlines through micromagnetic heterostructure devices

Photocurrent in quantum materials is often collected at global contacts far away from the initial photoexcitation. This collection process is highly nonlocal. It involves an intricate spatial pattern of photocurrent flow (streamlines) away from its primary photoexcitation that depends sensitively on the configuration of current collecting contacts as well as the spatial nonuniformity and tensor structure of conductivity. Direct imaging to track photocurrent streamlines is challenging. Here, we demonstrate a microscopy method to image photocurrent streamlines through ultrathin heterostructure devices comprising platinum on yttrium iron garnet (YIG). We accomplish this by combining scanning photovoltage microscopy with a uniform rotating magnetic field. Here, local photocurrent is generated through a photo-Nernst type effect with its direction controlled by the external magnetic field. This enables the mapping of photocurrent streamlines in a variety of geometries that include conventional Hall bar-type devices, but also unconventional wing-shaped devices called electrofoils. In these, we find that photocurrent streamlines display contortion, compression, and expansion behavior depending on the shape and angle of attack of the electrofoil devices, much in the same way as tracers in a wind tunnel map the flow of air around an aerodynamic airfoil. This affords a powerful tool to visualize and characterize charge flow in optoelectronic devices.

Ultrathin NiO/Ni3S2 Heterostructure as Electrocatalyst for Accelerated Polysulfide Conversion in Lithium–Sulfur Batteries

The practical application of Lithium–Sulfur batteries largely depends on highly efficient utilization and conversion of sulfur under the realistic condition of high‐sulfur content and low electrolyte/sulfur ratio. Rational design of heterostructure electrocatalysts with abundant active sites and strong interfacial electronic interactions is a promising but still challenging strategy for preventing shuttling of polysulfides in lithium–sulfur batteries. Herein, ultrathin nonlayered NiO/Ni3S2 heterostructure nanosheets are developed through topochemical transformation of layered Ni(OH)2 templates to improve the utilization of sulfur and facilitate stable cycling of batteries. As a multifunction catalyst, NiO/Ni3S2 not only enhances the adsorption of polysulfides and shorten the transport path of Li ions and electrons but also promotes the Li2S formation and transformation, which are verified by both in‐situ Raman spectroscopy and electrochemical investigations. Thus, the cell with NiO/Ni3S2 as electrocatalyst delivers an area capacity of 4.8 mAh cm−2 under the high sulfur loading (6 mg cm−2) and low electrolyte/sulfur ratio (4.3 μL mg−1). The strategy can be extended to 2D Ni foil, demonstrating its prospects in the construction of electrodes with high gravimetric/volumetric energy densities. The designed electrocatalyst of ultrathin nonlayered heterostructure will shed light on achieving high energy density lithium–sulfur batteries.

Interfacial interaction driven enhancement in the colossal magnetoresistance property of ultra-thin heterostructure of Pr0.6Sr0.4MnO3 in proximity with Pr0.5Ca0.5MnO3

The ultra-thin heterostructure of Pr0.6Sr0.4MnO3(15 nm)/Pr0.5Ca0.5MnO3(15 nm)/SrTiO3 fabricated using pulsed laser deposition technique exhibits the phase-segregated nature wherein the ferromagnetism of Pr0.6Sr0.4MnO3, and the antiferromagnetic state of Pr0.5Ca0.5MnO3 coexist in proximity. The observation of two exciting phenomena in the grown ultra-thin heterostructure, namely, the kinetic arrest and training effect, confirms its phase-segregated nature. The melting of the antiferromagnetic state in Pr0.5Ca0.5MnO3 into a ferromagnetic state due to the interfacial interaction arising from the magnetic proximity of the ferromagnetic clusters of Pr0.6Sr0.4MnO3 have been observed. A metal–insulator transition (TMIT) found at 215 K, close to its Curie temperature (TCurie) observed at 230 K, reveals a strong correlation between the electrical transport and the magnetization of the ultra-thin heterostructure. The electrical conduction in the high-temperature regime is explained in terms of the adiabatic small polaron hopping model. While the resistance in the metallic regime for temperatures above 100 K is contributed by the inelastic scattering due to the two-magnons, in the metallic regime below 100 K, the one-magnon inelastic scattering contribution is prevalent. An enhanced colossal magnetoresistance property near room temperature is obtained in the ultra-thin heterostructure arising from the proximity-driven interfacial interaction, making it a suitable candidate for technological applications near room temperature.

Construction of Ultrathin Layered MXene-TiN Heterostructure Enabling Favorable Catalytic Ability for High-Areal-Capacity Lithium–Sulfur Batteries

HighlightsAn in-situ strategy to synthesize ultrathin two-dimensional MXene-TiN heterostructures and the ultrathin structure extremely shortens the electrons diffusion distance from catalysts to active sulfur species.The heterostructure exhibits superior electronic structures to strongly capture the polysulfides and enhance bidirectional electrocatalytic ability between LiPSs and Li2S.The advanced cathode achieves an excellent long-term cyclability with an extremely low-capacity fading rate of 0.022% over 1000 cycles and a remarkable areal capacity of 8.27 mAh cm−2 at high sulfur loading of 10.16 mg cm−2.

Ultrathin scroll-like CdSe/CdS core/crown heteronanoplatelets: Colloidal synthesis and properties

We report the synthesis and the optical properties of a new type of scroll-like CdSe/CdS core/crown nanoplatelets (NPLs), based on the ultrathin rolled-up CdSe core NPLs with the laterally epitaxial grown of CdS crowns. This typical synthesis pathway is explored by optimizing crowns growth temperatures and precursor injection conditions by a high-efficiency one-step strategy, thus controlling the ultrathin thickness of scrolled CdS crowns at the monolayer level. These novel ultrathin nanoroll-like core/crown NPLs not only have excellent optical properties with the ultra-narrow emission spectra, but also given the improved photoluminescence efficiency and enhanced photostability in the blue light region. Importantly, the broad trap emission in core/crown hetero-NPLs is completely suppressed by a photo-annealing process, which could avoid the significant adverse effects on intrinsic emission and keep their emission intensity of ~90%. Therefore, this work proposes a useful strategy for synthesizing ultrathin scrolled core/crown NPLs heterostructures, which paves the way for fabricating high-efficiency and stable ultrathin NPL-based heterostructure materials in the blue-violet emission band.

In-situ construction of ultrathin MoP-MoS2 heterostructure on N, P and S co-doped hollow carbon spheres as nanoreactor for efficient hydrogen evolution

Rational design hierarchical nano-heterojunction electrocatalysts with high activity and durability for hydrogen evolution reaction (HER) are attractive for sustainable energy conversion. Here, one-step and space-confine pyrolysis strategy is demonstrated to in-situ construct ultrathin MoP-MoS2 heterostructure on N, P and S co-doped hollow carbon spheres (MoP-MoS2/HCSs) that present remarkable HER performance. The intimate contact among MoP outer-layer, MoS2 intermediate layer and N, P and S co-doped HCSs inner-layer facilitates the formation of triple-shelled heterogeneous nanoreactor. Benefiting from abundant active sites, high specific surface area, heteroatomic doping, intimate catalyst-substrate contact and ultrathin active heterostructure, the resulting MoP-MoS2/HCSs not only displays significant electrocatalytic activity with low overpotentials (71 mV and 125 mV in 1.0 M KOH and 0.5 M H2SO4, respectively) at current density of 10 mA cm−2, but exhibits outstanding stability toward HER process. This study offers a promising approach to design hierarchical nano-heterojunction with remarkable electrochemical properties for green energy development.

Two-step electrodeposition synthesis of heterogeneous NiCo-layered double hydroxides@MoO3 nanocomposites on nickel foam with high performance for hybrid supercapacitors

Reasonable assembly and heterogeneous growth using new energy storage materials is a popular and promising method to ameliorate the electrochemical performance of hybrid supercapacitors. Herein, a unique intercalation pseudocapacitance characteristics and battery-type electrode materials layered double hydroxides (LDHs) nanosheet arrays are obtained by a simple and environmentally pollution-free two-step electrodeposition technology. The electrode materials are composed of MoO3 and NiCo-layered double hydroxides (NiCo-LDH), which was directly grown on the three-dimensional (3D) conductive nickel foam (NF) substrate, forming a binder free two-dimensional (2D) ultra-thin cross-multilayer heterostructure (NiCo-LDH@MoO3/NF). The heterogeneous NiCo-LDH@MoO3/NF nanomaterial manifests a prominent specific capacity of 952.2 C g−1 at the current density of 1 A g−1, and also delivers good cycling performance of 86.42% capacity retention at current density of 20 A g−1 after 10,000 cycles. Remarkably, the fabricated NiCo-LDH@MoO3/NF//AC HSC equipment shows an excellent energy density, whose value is 58.06 Wh kg−1 with the power density of 800 W kg−1, and the capacity retention rate and coulombic efficiency can reach 73% and 96.7% at 15 A g−1, respectively, suggesting that it has application prospects in supercapacitor electrode materials.

Large‐Area Tellurium/Germanium Heterojunction Grown by Molecular Beam Epitaxy for High‐Performance Self‐Powered Photodetector

AbstractAs an attractive elemental semiconductor material, p‐type tellurium (Te) with a narrow bandgap provides high carrier mobility, strong light–matter interactions in a wide spectral range, and good chemical stability, which enlightens the potential in optoelectronic devices. However, the applications are impeded by weak carrier separation and vague potential in scaling‐up. In this work, the integration of Te and conventional semiconductor germanium (Ge) is designed. Through molecular beam epitaxy (MBE) method, large‐area and uniform Te films with high crystallinity are directly deposited on the Ge substrates. The difference in work function between Te and Ge layer leads to a built‐in electric field, which can effectively enhance the carrier separation. As a result, a self‐powered splendid photovoltaic performance is observed in the MBE grown Te/Ge vertical heterojunction with current on/off ratio over 103, responsivity (R) 523 mA W−1, and specific detectivity (D*) 9.50 × 1010 cm Hz1/2 W−1 when illuminated by near‐infrared light (980 nm, 2.15 µW cm−2). Furthermore, excellent stability and high response speed of the ultrathin heterostructure offer a significant application value for multipurpose photoelectric devices.

One-step hydrothermal synthesized 3D P–MoO3/FeCo LDH heterostructure electrocatalysts on Ni foam for high-efficiency oxygen evolution electrocatalysis

Low-cost yet high-efficiency oxygen evolution reaction (OER) catalysts have attracted ardent attention to speed up the development of water electrolysis. Recent researches have shown that layered double hydroxides (LDH) are promising candidates towards OER, but further improvement is still highly demanded for its large-scale practical application in water splitting. Herein, we report a 3D P-doped MoO3/FeCo LDH/NF (P–MoO3/FeCo LDH/NF) ultrathin nanosheet heterostructure electrocatalyst with an extremely low overpotentials of 225 mV for delivering a current density of 10 mA cm−2 for OER and a great durability for at least 80 h by a simple one-step hydrothermal method. Extraordinarily, the P–MoO3/FeCo LDH catalyst achieves a high current density of 300 mA cm−2 and even 350 mA cm−2 at an extremely low overpotential of 297 mV and 302 mV, respectively, which is crucial for the water electrolysis industry. The remarkable performance may be attributed to that the heterostructure between P–MoO3 and FeCo LDH not only optimizes electronic structure, thus inducing electron transfer from P–MoO3 to FeCo LDH and then realizing fast electron transfer rates, but also produces more catalytic active sites. Moreover, the synergetic effect between MoO3 and FeCo LDH also plays an essential role for enhancing the catalytic performances. This work explores the effect of phosphomolybdic acid on the structure, composition and performances of FeCo LDH catalysts, and also provides a simple and cost-effective way to prepare high-efficiency and low-cost layered double hydroxide electrocatalysts for OER.

"One stone, two birds": engineering 2-D ultrathin heterostructure nanosheet BiNS@NaLnF4 for dual-modal computed tomography/magnetic resonance imaging guided, photonic synergetic theranostics.

It is interesting yet challenging to design theranostic nanoplatforms for the accurate diagnosis and therapy of diseases; these nanoplatforms consist of single contrast-enhanced imaging or therapeutic agents, and they possess their own unique shortcomings that limit their widespread bio-medical applications. Therefore, designing a potential theranostic agent is an emerging approach for the synergistic diagnosis and therapeutics in bio-medical applications. Herein, a lanthanide-loaded (NaLnF4) heterostructure BiOCl ultrathin nanosheet (BiNS@NaLnF4) as a theranostic agent was synthesized facilely by a solvothermal protocol. BiNS@NaLnF4 was employed as a multi-modal contrast agent for computed tomography (CT) and magnetic resonance imaging (MRI), showing a high-performance X-ray absorption contrast effect, an outstanding T1-weighted imaging function result, good cytocompatibility and favorable in vivo effective imaging for CT. Notably, BiNS@NaLnF4 was applied to achieve a satisfactory photon-thermal conversion efficiency (35.3%). Moreover, the special heterostructure barrier achieved increased utilization of electrons/holes, enhancing the generation of reactive oxygen species (ROS) under visible-light irradiation to further expand the therapeutic effect. Dramatically, visible light emission with the up-conversion law was employed to stimulate ROS after irradiation with a 980 nm laser. Simultaneously, the as-prepared BiNS@NaLnF4 can be applied in photothermal/photodynamic therapy (PTT/PDT) investigation for tumor ablation. In summary, the results reveal that BiNS@NaLnF4 is a potential multi-modal theranostic candidate, providing new insights for synergistic theranostics of tumors.

A flower-cluster heterogenous structure assembled by ultrathin NiCo/NiCoOx-SiO2 nanobelts with stable catalytic performance

Ultrathin two-dimensional heterogeneous structural with large specific surface area have abundant interface defects and changed surface state, which provides a mass of active sites. This novel structure can obviously enhance catalytic performance and have received researcher’s attention. Herein, a tactful way has been explored to synthesize a flower-cluster heterogenous structure NiCo/NiCoOx-SiO2 assembled by ultrathin nanobelts through coordination controlling coprecipitation in hydrothermal system followed by H2 in-situ reduction. NiCo alloy nanophase uniformly dispersed on the stable ultrathin NiCoOx-SiO2 nanobelts. Based on the favorable reactant transmission of the flower-clustered ultrathin 2D heterogeneous structure and the stabilized NiCo active sites via strong interaction with NiCoOx-SiO2, the as-obtained NiCo/NiCoOx-SiO2 nanocatalyst shows excellent stable catalytic performance, which allows over 25 recycles without obvious performance decay for the amination of p-nitrophenol and maintaining 100 % conversion even after 7 days for CO oxidation reaction at 400 °C. This work provides a new way to construct a stable, non-noble metal ultrathin heterostructure nanocatalyst with superior catalytic degradation performance of environmental pollutants for the requirement of green chemistry.

Simultaneous formation of Bi2O2(OH)(NO3)/BiOBr ultrathin hierarchical microspheres for effectively promoting visible-light-driven photocatalytic activity in environmental remediation

As a two-dimensional nanomaterial, bismuth oxybromide (BiOBr) have attracted tremendous interest in the area of visible-light photocatalysis since it can provide the internal electric field (IEF) through z-axis through its unique electronic band structure. However, the insufficient active sites and rapid recombination rate of charged carriers hamper the efficiency of the photocatalysis. To address these two major obstacles, an enticing strategy of constructing heterojunction was established by introducing Bi2O2(OH)(NO3) (BiON) in BiOBr with the same precursor. Through a facile one-pot hydrothermal synthesis, two Sillén-type layered photocatalysts, with intimately constructed ultrathin heterostructure, was synthesized by the co-precipitation method. In this work, the formation of Bismuth-based heterojunction for charge separation is established by the excessive bismuth nitrate, which subsequently participates with the in situ growth of ultrathin hierarchical microspheres. By attenuating the thickness of BiOBr from 20 nm to 8 nm with the aid of BiON, the photogenerated charges could migrate to the active sites through shorter charge diffusion pathway. Also, the BiOBr and BiON act as an active bridge to promote the separation of electron-hole pairs, which also brings out more active sites due to its increased specific surface area. BiON/BiOBr ultrathin hierarchical microspheres exhibited enhanced visible-light photocatalytic activity for decontaminating several types of pollutants. Besides, the activity of as-prepared BiON/BiOBr was further evaluated by inhibiting the growth of kanamycin-resistant bacteria strains. This study presents a novel strategy to incorporate the crystalline bismuth hydrate nitrate into BiOBr to form ultrathin hierarchical microspheres with high surface area for environmental remediation.

Ultrathin low dimensional heterostructure composites with superior photocatalytic activity: Insight into the multichannel charge transfer mechanism

Abstract Multi-level and multi-angle designations of photocatalysts have attracted great attention to address the insufficient photogenerated charge generation and transformation in photocatalysis. In this study, we reported an ultrathin 1D/2D W18O49/g-C3N4 nanocomposites with unique multiscale structure and electronic property through direct growth of 1D plasmonic W18O49 nanowires onto the surface of 2D ultrathin g-C3N4 nanosheets. Owing to the unique multiscale structure and electronic property, the synthesized nanocomposites present enhanced photocatalytic activity, owns the maximum removal efficiency of 96.3% and rate constant of 0.0464 min−1 for Ibuprofen (IBF) after 60 min under AM 1.5G light. Meanwhile, under near-infrared (NIR) light irradiation, the optimum UWN-3 present 39.2% removal efficiency of IBF and the reaction rate reached 0.0027 min−1 after 120 min. Additionally, the degradation pathway indicated that the decarboxylation process was the main decomposition route of IBF in this reaction system, and OH radical species attack process also contributed to the degradation of IBF. Scavenge experiments and mechanism analysis illustrated that IBF degradation in this reaction system mainly depends on h+, O2– and OH radical species, and the promoted photocatalytic performance of the synthesized ultrathin 1D/2D W18O49/g-C3N4 nanocomposites are stem from the synergism of the multichannel photogenerated charge transfer pathways. The combination of the multichannel charge transfer pathways mentioned above resulted in the highly efficient photocatalytic activity of the ultrathin 1D/2D W18O49/g-C3N4 nanocomposites.

Vertical van der Waals Heterostructure of Single Layer InSe and SiGe

We present a first-principles investigation on the stability, electronic structure and mechanical response of ultra-thin heterostructure composed of single layers of InSe and SiGe. First, by per- forming total energy optimization and phonon calculations, we show that single layers of InSe and SiGe can form dynamically stable heterostructures in 12 different stacking types. Valence and conduction band edges of the heterobilayers form a type-I heterojunction having a tiny bandgap ranging between 0.09-0.48 eV. Calculations on elastic-stiffness tensor reveal that two mechanically soft single layers form a heterostructure which is stiffer than constituent layers due to relatively strong interlayer interaction. Moreover, phonon analysis show that the bilayer heterostructure has highly Raman active modes at 205.3 and 43.7 cm −1 , stemming from out-of-plane interlayer mode and layer breathing mode, respectively. Our results show that, as a stable type-I heterojunction, ultra-thin heterobilayer of InSe/SiGe holds ...

Construction of uniform SnS2/ZnS heterostructure nanosheets embedded in graphene for advanced lithium-ion batteries

Lithium-ion batteries have been broadly used in energy storage systems and power batteries. However, the current research on LIBs anodes still faces key problems such as low specific capacity, limited cycle life and low initial coulombic efficiency, which limit its commercial applications. In order to solve these issues, SnS2/ZnS heterostructure nanosheets are synthesized on a reduced graphene oxide (expressed as SnS2/ZnS-rGO) derived from ZnSn(OH)6 through the solution sulfidation method. This composite has the features of two-dimensional ultrathin nanosheets and heterostructure, which can shorten Li+ diffusion distance, and provide additional charge transfer driving force. The three-dimensional (3D) SnS2/ZnS-rGO electrode represents high specific capacity (1458.3 mA h g−1 at 0.2 A g−1) and outstanding cycle stability of 4000 cycles (432.4 mA h g−1 at 10 A g−1). This unique lithium storage mechanism has been studied by in-situ and ex-situ XRD techniques in detail. This work not only provides a feasible method for the preparation of bimetallic sulfides, but also gives a novel application prospect for the new self-built high energy density anode.

Role of SnS2 in 2D–2D SnS2/TiO2 Nanosheet Heterojunctions for Photocatalytic Hydrogen Evolution

Constructing heterojunctions with face-to-face interface is a new avenue for accelerating the charge separation in semiconductor photocatalysts toward highly efficient solar water splitting systems. Here, a novel SnS2/TiO2 2D–2D ultrathin nanosheet heterostructure was fabricated via a hydrothermal route in two steps. The obtained 2D–2D SnS2/TiO2 nanojunction has not only provided large contact areas but also shortened the charge transport distance, resulting in significantly enhanced photocatalytic H2 evolution property. The H2 generation rate obtained for the optimized sample reaches 652.4 μmol h–1g–1, far exceeding (∼8 times) that of pristine TiO2 and SnS2 ultrathin nanosheets under simulated solar irradiation. Moreover, further analysis reveals a photoinduced carrier transfer from TiO2 to SnS2 at the interface junction, which causes a partial reduction of the SnS2 cocatalyst to SnS in the nanocomposite during the photocatalytic reactions. These results not only demonstrate that the construction of 2D–2...