Heterostructure Composites Research Articles

One-Step Cooperative Growth of High Reaction Kinetics Composite Homogeneous Core-Shell Heterostructure.

Reaction kinetics can be improved by the enhanced electrical contact between different components growing symbiotically. But so far, due to the necessity for material synthesis conditions match, the component structures of cooperative growth are similar, and the materials are of the same type. The collaborative growth of high-reaction kinetics composite homogeneous core-shell heterostructure between various materials is innovatively proposed with different structures in one step. The NiCo-LDH and PPy successfully symbiotically grow on activated carbon fiber fabric in one step. The open channel structure of the NiCo-LDH nanosheets is preserved while PPy effectively wrapped around the NiCo-LDH. The well-defined nanostructure with abundant active sites and convenient ion diffusion paths is favorable for electrolyte entry into the entire nanoarrays. In addition, owing to the enhanced electronic interaction between different components through XPS analysis, the NiCo-LDH@PPy electrode shows outstanding reaction kinetics and structural stability. The as-synthesized NiCo-LDH@PPy exhibited excellent super-capacitive storage capabilities, robust capacitive activity, and good rate survival. Furthermore, an asymmetric supercapacitor (ASC) device made of NiCo-LDH@PPy and activated carbon (AC) is able to maintain a long cycle life while achieving high power and energy densities.

Facile fabrication of N-doped heterostructured hybrid particles based on montmorillonite incorporated with g-C3N4 for enhanced hydrogen production by NaBH4 in methanol

As an alternative to the currently increasing use of fossil fuels, hydrogen has become very important as a clean energy carrier. Herein, facile fabrication of N doped-heterostructured hybrid particles based montmorillonite (M) incorporated on graphitic carbon nitride (g-C3N4) with calcination and hydrothermal nitric acid activation was performed. The N-doped heterostructured g-C3N4-M hybrid material was used as a metal-free hybrid catalyst for NaBH4 dehydrogenation in methanol for the first time. The hydrogen generation rate (HGR) of 11,200 ml min−1 g−1 in methanol was obtained. XRD, SEM, FTIR, EDS, XPS and nitrogen adsorption/desorption analyses were used to characterize the physicochemical properties of heterostructured composites. Also, the mechanism of catalytic activity was evaluated with the obtained N-doped g-C3N4-M hybrid material.

Regulating In-MOF derivatives for bidirectionally boosting redox kinetics of sulfur cathodes

Lithium sulfur (Li–S) batteries are regarded as a promising application device due to their high theoretical capacity and energy density. However, the commercialization of Li–S batteries is restricted due to their fast capacity fading caused by the shuttle effect of lithium polysulfide (LiPSs) and slow redox reaction of sulfur cathodes. Designing highly-active bidirectional electrocatalysts is an effective strategy to address the problems caused by complex multi-step reactions. Herein, the phase of In-metal-organic framework (In-MOF) derivatives are regulated by controlling the carbonization temperature, and In–In2O3@C heterostructure composite can be obtained at 800 °C. The results show that the polar In2O3 can not only effectively adsorb LiPSs but also accelerate the conversion from Li2S8 to Li2S4, and In can promote the conversion from Li2S4 to Li2S and simultaneously lower the dissociation energy barrier of Li2S. Due to the different catalytic functions of In and In2O3 for different reaction stages of Li–S batteries, In–In2O3@C shows bidirectionally catalytic effect, and renders the corresponding batteries achieve the best electrochemical properties. The specific discharge capacity of In–In2O3@C/S can reach 1298.5 mAh g−1 at 0.2 C after three cycles of activation, and it keeps 620.9 mAh g−1 after 80 cycles with Coulombic efficiency of approximate 100 %. Regulating the products of MOF derivatives provides a reference for the regulation of catalysts for Li–S batteries.

Spatial hetero-structured composites with ultrawide linear range for positive-negative pressure sensing and e-skin of bionic fish

For impelling practical applications of flexible sensors or electronic skins, it is challenging and urgent to fabricate multifunctional flexible mechanical sensors with good linearity over a wide working range in an economical and scalable manner. Currently, it is immensely difficult to simultaneously detect tension, pressure and bending with high linearity over a wide strain range by using one film without sensor integration. Herein, we present a porous flexible mechanical sensor with a spatial electron transport network consisting of ethylene-α-octene random copolymer (ORC) elastic skeleton with surface embedded carbon black (CB) and carbon fiber (CF) bridges. Such an interesting spatial hetero-structure can shunt the electron transport effectively to regulate the resistance change of the sensor during strain loading, resulting in linear electrical signal response to mechanical deformation for a tensile strain up to 320% and a pressure up to 1.3 MPa, as well as a bending angle ranging from− 90 o to 90 o, respectively. Besides, it shows the detection capability of ambient pressure ranging from −0.09 MPa to 0.4 MPa continuously. Such a multifunctional film sensor with ultrawide linear working range demonstrates potential applications for monitoring body motions of athletics and underwater soft robots.

Tungsten Nitride/Tungsten Oxide Nanosheets for Enhanced Oxynitride Intermediate Adsorption and Hydrogenation in Nitrate Electroreduction to Ammonia.

Electrochemical NO3- reduction reaction (NO3RR) is a promising technique for green NH3 synthesis. Tungsten oxide (WO3) has been regarded as an effective electrocatalyst for electrochemical NH3 synthesis. However, the weak adsorption and the sluggish hydrogenation of oxynitride intermediates (NOx, e.g., *NO3 and *NO2) over WO3 materials hinder the efficiency of converting NO3- to NH3. Herein, we design a heterostructure of tungsten nitride (WN) and WO3 (WN/WO3) nanosheets to optimize *NO3 and *NO2 adsorptions and facilitate *NO2 hydrogenations to achieve a highly efficient electrochemical NO3RR to produce NH3. Theoretical calculations predict that locally introducing WN into WO3 will shorten the distance between adjacent W atoms, resulting in *NO3 and *NO2 being strongly adsorbed on W active sites in the form of bidentate ligands instead of the relatively weak monodentate ligands. Furthermore, WN facilitates H2O dissociation to supply the requisite protons, which is beneficial for *NO2 hydrogenations. Inspired by theoretical prediction, WN/WO3 nanosheets are successfully fabricated through a high-temperature nitridation process. The transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption near-edge spectroscopy investigations confirm that the amorphous WN has been locally introduced in situ into WO3 nanosheets to form a composite heterostructure. The as-prepared WN/WO3 nanosheets exhibit a high Faraday efficiency of 88.9 ± 7.2% and an appreciable yield rate of 8.4 mg h-1 cm-2 toward NH3 production, which is much higher than that of individual WO3 and WN. The enhanced adsorption and hydrogenation behaviors of *NOx over WN/WO3 are characterized by in situ Fourier-transform infrared spectroscopy, consistent with the theoretical predictions. This work develops facile and effective heterostructure nanomaterials to tune the adsorption and hydrogenation of NOx for boosting the efficiency from NO3- to NH3.

Construction of FeSbO4-Sb2O4 hetero-nanocrystals anchored on reduced graphene oxide sheets for superior lithium and sodium storage

Antimony-based oxides with conversion-alloying/dealloying mechanism have attracted great attentions as alternative anode materials for lithium/sodium-ion batteries due to their high theoretical capacities. However, slow reaction kinetics, inherent poor conductivity and large volume change severely inhibit their practical application. Herein, a novel composite with FeSbO4-Sb2O4 hetero-nanocrystals anchored on reduced graphene oxide (rGO) sheets is designed and successfully constructed by a facile solvothermal method. The intense interaction between Fe3+ and Sb5+ oxidized from Sb3+ by graphene oxide (GO) boosts priority formation of rutile FeSbO4 nanoparticles. And the excess Sb3+ and Sb5+ subsequently generate nano-sized cervantite Sb2O4 to form FeSbO4-Sb2O4 hetero-interface. Such unique structure not only can enhance electrical conductivity and structural stability of electrode, but also shorten diffusion distance of lithium/sodium ions during discharge/charge processes. Moreover, the in-situ generated Fe during electrochemical reaction can boost lithium/sodium release from Li2O/Na2O. Attributed to the unique structure, the as-obtained FeSbO4-Sb2O4/rGO-200 electrode delivers greatly improved electrochemical performance for both lithium and sodium storage, including large reversible capacities, high rate capability, and superior long-term cycling stability. This work provides an efficient route to rationally design and synthesize hetero-structural composites boosting lithium-/sodium-storage properties.

Multicolor x-rays from free electron-driven van der Waals heterostructures.

The emergence of van der Waals (vdW) heterostructures has led to precise and versatile methods of fabricating devices with atomic-scale accuracies. Hence, vdW heterostructures have shown much promise for technologies including photodetectors, photocatalysis, photovoltaic devices, ultrafast photonic devices, and field-effect transistors. These applications, however, remain confined to optical and suboptical regimes. Here, we theoretically show and experimentally demonstrate the use of vdW heterostructures as platforms for multicolor x-ray generation. By driving the vdW heterostructures with free electrons in a table-top setup, we generate x-ray photons whose output spectral profile can be user-customized via the heterostructure design and even controlled in real time. We show that the multicolor photon energies and their corresponding intensities can be tailored by varying the electron energy, the electron beam position, as well as the geometry and composition of the vdW heterostructure. Our results reveal the promise of vdW heterostructures in realizing highly versatile x-ray sources for emerging applications in advanced x-ray imaging and spectroscopy.

Development of a Composite Heterostructure Electrolyte for Low-Temperature Ceramic Fuel Cells: CaSnO3–ZnO Semiconductor Design and Optimization

Development of a Composite Heterostructure Electrolyte for Low-Temperature Ceramic Fuel Cells: CaSnO₃–ZnO Semiconductor Design and Optimization

Accelerated design of stable halide perovskite heterostructure film in hostile condition via surface modifier

The bulk halide perovskite heterostructure has been adopted for perovskite-based optoelectronic devices owing to their interesting interfacial phenomena; however, most of them are unstable in hostile condition and the extremely large virtual design space causes problems for traditional trial-and-error methods to optimize them. In this study, we combine photoelectrochemical experiments, machine learning and first-principles calculations (Exp + ML + DFT) to accelerate the design of halide perovskite heterostructures in aqueous solution, in an effort to improve stability of halide perovskite materials in hostile condition (prototypical CH3NH3PbI3 quickly deactivates in water within seconds). The optimization of halide perovskite heterojunction with surface modifier is speeded up via machine learning using extra tree algorithm, and a large virtual design space consisting of halide perovskite heterostructure composites is predicted. Five new water-stable perovskite heterostructure candidates predicted via machine learning are experimentally validated, and the first-principles calculations reveal the detailed atomic and electronic structures of an exemplar stable heterostructure candidate. This study demonstrates the effectiveness of machine learning to accelerate the design of stable halide perovskite heterostructure materials in hostile condition.

Interfacial charge density modulation by coupling CeO2 with dual-phase NiS/Ni3S2 to accelerate alkaline water splitting

To improve the catalytic kinetics for water electrolysis, it is essential to apply oxygen vacancies and heterojunction engineering simultaneously to electrocatalysts and enhance the ad/desorption process of intermediate substances (H*, OH*, O*, OOH*). Nevertheless, the synergistic effect of these two strategies in eutectic nickel sulfide composite materials has not received systematic investigation. In this study, a self-supported NiS/Ni3S2/CeO2 composite heterostructure comprising NiS/Ni3S2 nanosheets and CeO2 nanoparticles as a dual-functional electrocatalyst was proposed. NiS/Ni3S2/CeO2 exhibits remarkable catalytic activity with an ultra-low overpotential of 85 mV at 10 mA cm−2 for HER and 300 mV at 50 mA cm−2 for OER. As a dual-function electrode, NiS/Ni3S2/CeO2 electrocatalysts require only 1.52 V battery potential to deliver 10 mA cm−2, outperforming Pt-based/RuO2-based metal catalysts. DFT calculations reveal that the interface coupled with CeO2 undergoes rapid charge recombination, leading to the introduction of many oxygen vacancies that can effectively adjust the electron density of neighboring Ni sites and optimize the H* adsorption binding force, thereby accelerating the overall kinetic process of water electrolysis. This work provides a reliable electronic structure adjustment strategy to fabricate highly cost-effective and durable electrocatalysts for overall water splitting.

Mn2+-Doped MoS2/MXene Heterostructure Composites as Cathodes for Aqueous Zinc-Ion Batteries.

Typical layered transition-metal chalcogenide materials, especially MoS2, are gradually attracting widespread attention as aqueous Zn-ion battery (AZIB) cathode materials by virtue of their two-dimensional structure, tunable band gap, and abundant edges. The metastable phase 1T-MoS2 exhibits better electrical conductivity, electrochemical activity, and zinc storage capacity compared to the thermodynamically stable 2H-MoS2. However, 1T-MoS2 is still limited by the phase stability and layered structure destruction for AZIB application. Thus, a three-dimensional interconnected network heterostructure (Mn-MoS2/MXene) consisting of Mn2+-doped MoS2 and MXene with a high percentage of 1T phase (82.9%) was synthesized by hydrothermal methods and investigated as the cathode for AZIBs. It was found that S-Mn-S covalent bonds between MoS2 interlayers and Ti-O-Mo bonds at heterogeneous interfaces can act as "electron bridges" to facilitate electron and charge transfer. And the doping of Mn2+ and the combination of MXene not only expanded the interlayer spacing of MoS2 but also maintained the metastable structure of 1T-MoS2 nanosheets, acting to reduce the activation energy for Zn2+ intercalation and enhance specific capacity. The obtained Mn-MoS2/MXene contains more 1T-MoS2 and provides an improved specific capacity of 191.7 mAh g-1 at 0.1 A g-1. Compared with Mn-MoS2 and pure MoS2, it also exhibits enhanced cycling stability with a capacity retention of 80.3% after 500 cycles at 1 A g-1. Besides, the conductivity of Mn-MoS2/MXene is significantly improved, which induces a lower activation energy of the zinc ions during intercalation/deintercalation.

Alkanolamine-Grafted and Copper-Doped Titanium Dioxide Nanosheets–Graphene Composite Heterostructure for CO2 Photoreduction

Alkanolamine-Grafted and Copper-Doped Titanium Dioxide Nanosheets–Graphene Composite Heterostructure for CO₂ Photoreduction

Tailoring the structure of MoS2/vertical graphene composites via chemical vapor deposition for hydrogen evolution reaction

Controlling the mutual structure between different materials in the heterostructured composites is of key importance in determining their properties and further applications. In this work, joint molybdenum disulfide (MoS2) nanosheets supported by vertically standing graphene (VSG) were fabricated by full chemical vapor deposition (CVD) method, thus leading to precisely tailoring the support-joint coupling structures between VSG support and joint MoS2 nanosheets in the as-fabricated MoS2/VSG or (MoS2-MoO3−x)/VSG hybrid architectures. Which were then directly used as effective, stable and binder-free electrodes for hydrogen evolution reaction (HER), and revealing that the CVD loading mode of MoS2 (or MoS2-MoO3−x) on VSG support in a vertically or obliquely inserted three-dimensional (3D) architecture has a key influence on improving their HER activities. These results shed light on structural design of multicomponent heterostructures by coupling engineering for various applications.

A dual-layer electrolyte of CuFeO2–ZnO for low-temperature solid oxide fuel cells

Semiconductor-based heterostructure composites with high ionic conductivity have gained considerable attentions as potential electrolytes for low temperature solid oxide fuel cells (LT-SOFCs). Thereinto, the p-n junction is designed for the built-in electric field, thus avoiding short-circuiting occurrence and implementing fuel cell functionality. Herein, a novel strategy to construct the dual-layer electrolyte using p-type CuFeO2 (CFO) and n-type ZnO respectively as individual layer is proposed. Electrochemical studies find that the fuel cell performance is significantly correlated with the weight ratios of CFO and ZnO phases. The device based on 3CFO-7ZnO (CFO in 30 wt% and ZnO in 70 wt%) electrolyte exhibits an open circuit voltage (OCV) of 1.06 V and a peak power density (PPD) of 557 mW cm−2 at 550 °C, apparently superior to both of the direct mixture of CFO-ZnO nanocomposite (468 mW cm−2) and single-phase ZnO electrolytes (300 mW cm−2) at the same operating temperature. Further investigations on energy band structure and rectifying characteristics related to the CFO and n-type ZnO indicate the existence of p-n junction. This work proposed a new method to design effective dual-layer semiconductor-based electrolytes for LT-SOFC.

Engineering the active sites by tuning the Ni and Mn composition in hierarchical heterostructured composites for electrocatalytic water splitting

Hydrogen production via electrochemical water splitting is a potentially clean and sustainable energy technology. Composition tuned binary NiMn oxides of Ni0.75Mn0.25O and Ni0.8Mn0.2O as an anode and cathode, respectively, demonstrate an excellent bifunctional electrocatalytic performance with a long term stability of 77 hours at a higher current density of 200 mA cm−2 toward overall water splitting (OWS) in an alkaline 1M KOH electrolyte solution. An anion exchange membrane H-type electrolytic cell requires a cell voltage of 1.74 V in order to generate a current density of 10 mA cm−2. The manganese oxide-modified nickel oxide nanosheets expedite the O–O bond formation via synergistic interaction between Ni3+ (t2g6eg1) and Jahn–Teller active Mn3+ (t2g3eg1). Moreover, due to their single electron occupancy in the eg orbital, the higher Mn3+ and NiO active sites could readily adsorb OH− ions from the electrolyte and promote a higher oxidation state, thereby accelerating the OER reaction. During OER, the energy and occupancy of these antibonding orbitals result in strong σ-bonds between these orbitals and oxygen-related adsorbate. Furthermore, the highest concentration of Ni(OH)2 attracts H+ ions, promoting the formation of H2.

Ultrahigh Capacitive Energy Density in Stratified 2D Nanofiller-Based Polymer Dielectric Films.

Dielectric capacitors are critical components in electronics and energy storage devices. The polymer-based dielectric capacitors have the advantages of device flexibility, fast charge-discharge rates, low loss, and graceful failure. Elevating the use of polymeric dielectric capacitors for advanced energy applications such as electric vehicles (EVs), however, requires significant enhancement of their energy densities. Here, we report a polymer thin film heterostructure-based capacitor of poly(vinylidene fluoride)/poly(methyl methacrylate) with stratified 2D nanofillers (Mica or h-BN nanosheets) (PVDF/PMMA-2D fillers/PVDF), that shows enhanced permittivity, high dielectric strength, and an ultrahigh energy density of ≈75 J/cm3 with efficiency over 79%. Density functional theory calculations verify the observed permittivity enhancement. This approach of using oriented 2D nanofillers-based polymer heterostructure composites is expected to be versatile for designing high energy density thin film polymeric dielectric capacitors for myriads of applications.

Synthesis of heterostructure composite (g-C3N4/phosphomolybdic acid) for synergistic piezo/photo-catalytic degradation of CR dye and S. aureus bacteria

In photocatalysis systems, piezocatalytic effect is widely utilized to achieve efficient separation of photo-produced carriers for powerfully decomposing organic contaminants and bacteria under both mechanical vibrations and visible illumination. Herein, an efficient heterogeneous composite of phosphomolybdic acid (PMA)-immobilized onto g-C3N4 has been constructed via ionothermal and impregnation methods. After characterization, the g-C3N4/PMA hybrid has been applied for piezophotocatalytic degradation of Congo red dye (CR) and bacterial inactivation of staphylococcus aureus (S. aureus) under visible-light illumination and ultrasonication. Compared with the photocatalysis, the g-C3N4/PMA hybrid exhibited improved piezophotocatalytic degradation of CR, reaching 99 % within only 60 min, indicating the piezoelectric polarization promotes considerably photocatalytic activity. Also, high bacterial inactivation performance (>94.0 %) has been obtained compared with pristine g-C3N4 and PMA samples after 180 min of visible-illumination/ultrasonication. These improved outcomes were due to the synergistic impact between high reversible redox capabilities of PMA with the controllable electronic structured of g-C3N4, and piezoelectric polarization, which acts as a driving force to prevent the recombination of generated charges, leading to an efficient separation rate and transfer of the photogenerated electrons-holes, and thus boosting degradation and bacterial inactivation efficiencies. The recommended mechanisms for piezophotocatalytic degradation of both CR dye and S. aureus bacteria have been clarified and supported by trapping experiments, which confirmed the significant roles of •O2– and electrons. The reusability investigations demonstrated the high stability performance of g-C3N4/PMA hybrid during five sequential piezophotocatalytic cycles.

Nonlinear magnetoelectric effect in a ring composite heterostructure

Objectives. The relevance of the study of magnetoelectric (ME) effect in ring ferromagnetic–piezoelectric heterostructures is due to the possibility of creating various ME devices having improved characteristics. A detailed investigation of the nonlinear ME effect in a ring composite heterostructure based on lead zirconate titanate (PZT) piezoceramics and Metglas® amorphous ferromagnetic (FM) alloy under circular magnetization is presented.Methods. The ME effect was measured by the low-frequency magnetic field modulation method. Excitation alternating- and constant magnetic bias fields were created using toroidal coils wound on a ring heterostructure for circular magnetization of the FM layer.Results. When excited with circular magnetic fields in a non-resonant mode, the ME ring heterostructure generates a nonlinear ME voltage of higher harmonics. The field and amplitude dependencies of the first three ME voltage harmonics were investigated. ME coefficients were obtained for the linear ME effect α(1) = 5.2 mV/(Oe·cm), the nonlinear ME effect α(2) = 6 mV/(Oe2·cm), and α(3) = 0.15 mV/(Oe3·cm) at an excitation magnetic field frequency f = 1 kHz. The maximum amplitudes of the 1st and 3rd harmonics were observed at a constant bias magnetic field H ~ 7 Oe, which is almost two times smaller than in planar PZT–Metglas® heterostructures.Conclusions. A nonlinear ME effect was observed and investigated in a ring heterostructure based on PZT piezoceramics and Metglas® amorphous FM alloy. Due to the absence of demagnetization during circular magnetization of the closed FM layer, nonlinear ME effects are detected at significantly lower amplitudes of the exciting alternating and constant bias magnetic fields as compared to planar heterostructures. The investigated ring heterostructures are of potential use in the creation of frequency multipliers.

Hollow Ti3C2T MXene@CoSe2/N-doped carbon heterostructured composites for multiphase electrocatalysis process in lithium-sulfur batteries

Hollow Ti3C2T MXene@CoSe2/N-doped carbon heterostructured composites for multiphase electrocatalysis process in lithium-sulfur batteries

ZnO-Bi2O3 Heterostructured Composite for the Photocatalytic Degradation of Orange 16 Reactive Dye: Synergistic Effect of UV Irradiation and Hydrogen Peroxide

The development of semiconductor photocatalysts has recently witnessed notable momentum in the photocatalytic degradation of organic pollutants. ZnO is one of the most widely used photocatalysts; however, its activity is limited by the inefficient absorption of visible light and the fast electron–hole recombination. The incorporation of another metal or semiconductor with ZnO boosts its performance. In this present study, a heterostructured ZnO-Bi2O3 composite was synthesized via a simple co-precipitation method and was investigated for the UV-driven photocatalytic degradation of the Reactive Orange 16 (RO16), a model textile dye. The successful fabrication of ZnO-Bi2O3 microstructures with crystalline nature was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The discoloration of the dye solution was quantified using UV–Vis spectroscopy to determine the photocatalytic efficiency. The photocatalytic activity results demonstrated that the photodegradation at ZnO-Bi2O3 heterojunction was more efficient and 300 and 33% faster than individual Bi2O3 and ZnO catalysts, respectively, an effect that is indicative of a synergistic effect. In the presence of ZnO-Bi2O3 particles, the UV light-driven activity for RO16 degradation was twice as high as in its absence. The influence of adding the oxidant H2O2 on the UV-induced photocatalytic degradation was investigated and the results revealed a two-time increase in the photocatalytic activity of ZnO-Bi2O3 compared to UV irradiation alone, which could be ascribed to a summative degradative effect between UV and H2O2. Hence, this approach holds the potential for environmentally friendly wastewater treatment.