Heterostructure Interface Research Articles

A waveguide-integrated self-powered van der Waals heterostructure photodetector with high performance at the telecom wavelength.

Two-dimensional (2D) materials are attractive candidates for high-performance photodetectors due to their wide operating wavelength and potential to integrate with silicon photonics. However, due to their limited atomic thickness and short carrier lifetime, they suffer from high driving source-drain voltages, weak light-matter interactions and low carrier collection efficiency. Here, we present a high-performance van der Waals (vdWs) heterostructure-based photodetector integrated on a silicon nitride photonic platform combining p-type black phosphorus (BP) and n-type molybdenum disulfide (MoS2). Owing to the efficient carrier separation process and dark current suppression at the junction interface of the vdWs heterostructure, high photodetectivity and a fast response speed can be achieved. A fast response time (∼2.08/3.54 μs), high responsivity (11.26 mA W-1), and a high light on/off ratio (104) operating in the near-infrared telecom band are obtained at zero bias. Our research highlights the great potential of the high-efficiency waveguide-integrated vdWs heterojunction photodetector for integrated optoelectronic systems, such as high-data-rate interconnects operated at standardized telecom wavelengths.

Epitaxial van der Waals contacts of 2D TaSe2-WSe2 metal-semiconductor heterostructures.

The electronic contact between two-dimensional (2D) transition metal dichalcogenide (TMD) semiconductors and metal electrodes is a formidable challenge due to the undesired Schottky barrier, which severely limits the electrical performance of TMD devices and impedes the exploration of their unconventional physical properties and potential electronic applications. In this study, we report a two-step chemical vapor deposition (CVD) growth of 2D TaSe2-WSe2 metal-semiconductor heterostructures. Raman mapping confirms the precise spatial modulation of the as-grown 2D TaSe2-WSe2 heterostructures. Transmission electron microscopy (TEM) characterization reveals that this two-step method provides a high-quality and clean interface of the 2D TaSe2-WSe2 heterostructures. Meanwhile, the upper 1T-TaSe2 is formed heteroepitaxially on/around the pre-synthesized 2H-WSe2 monolayers, exhibiting an epitaxial relationship of (20-20)TaSe2//(20-20)WSe2 and [0001]TaSe2//[0001]WSe2. Furthermore, characterization studies using a Kelvin probe force microscope (KPFM) and electrical transport measurements present compelling evidence that the 2D metal-semiconductor heterostructures under investigation can improve the performance of electrical devices. These results bear substantial significance in augmenting the properties of field-effect transistors (FETs), leading to notable improvements in FET mobility and on/off ratio. Our study not only broadens the horizons of direct growth of high-quality 2D metal-semiconductor heterostructures but also sheds light on potential applications in future high-performance integrated circuits.

Enhanced photoelectrochemical oxidation of glycerol to dihydroxyacetone coupled with hydrogen generation via accelerative middle hydroxyl dehydrogenation over a Bi0/Bi3+ interface of a cascade heterostructure

A unique photoanode composed of spatially ternary WO3/BiVO4/Bi cascade heterostructure with Bi0/Bi3+ interface is constructed and exhibits a high glycerol conversion rate of 379.9 mmol m−2 h−1, DHA selectivity of 60.6% and high stability.

Photo-controllable heterostructured crystals of metal-organic frameworks via reversible photocycloaddition.

Metal-organic framework (MOF)-based heterostructures are attractive because they can provide versatile platforms for various applications but are limited by complex liquid epitaxial growth methods. Here, we employ photolithography to fabricate and control MOF-based heterostructured crystals via [4 + 4] photocycloaddition. A layered dysprosium-dianthracene framework, [Dy(NO3)3(depma2)1.5]·(depma2)0.5 (2) [depma2 = pre-photodimerized 9-diethylphosphonomethylanthracene (depma)] underwent a single-crystal-to-single-crystal transition at 140 °C to form [Dy(NO3)3(depma)(depma2)]·(depma2)0.5 (3). The dissociated anthracene moieties are face-to-face π-π interacted allowing a reversible photocycloaddition between 2 and 3. This structural transformation causes a luminescence switch between blue and yellow-green and thus can be used to fabricate erasable 2 + 3 heterostructured crystals for rewritable photonic barcodes. The internal strain at the heterostructure interface leads to photobending and straightening of the crystal, a photomechanical response that is fast, reversible and durable, even operating at 140 °C, making it promising for photoactuation. This work may inspire the development of intelligent MOF-based heterostructures for photonic applications.

Enhanced Raman scattering based on a ZnO/Ag nanostructured substrate: an in-depth study of the SERS mechanism.

Combining semiconductor and noble metal nanostructures into a hybrid system has shown many complementary advantages in the optical properties, making them more attractive in practical applications. Herein, we prepared a semiconductor/noble metal hybrid system composed of Ag nanoparticles decorated on ZnO nanoplates acting as a surface-enhanced Raman scattering (SERS) substrate for probing methyl red. The tuning of the optical characteristics of the hybrid system was demonstrated through the changes in the absorption, fluorescence, and Raman spectra. The formation of the local electromagnetic field at the heterostructure interface plays a pivotal role in its SERS activity. Thanks to density functional theory calculations, methyl red's vibrational modes and symmetry properties were assigned to be consistent with the contribution of the neutral trans conformer and protonated state. Then, using Herzberg-Teller-surface selection rules, these assignments strongly support the realization that the SERS mechanism based on the ZnO/Ag substrate has a significant electromagnetic contribution versus the Ag substrate in which charge transfer plays a pivotal role. To the best of our knowledge, this is the first investigation that has clarified the mechanism and advantage of semiconductor/metal (ZnO/Ag nanostructures) even over noble metals (Ag nanoparticles) in SERS applications. Moreover, the SERS behavior based on the ZnO/Ag substrate was also examined and the results indicated high sensitivity and good repeatability.

Highly responsive SnSe/GaN heterostructure-based UVC-SWIR broadband photodetector

Broadband photodetection spans the ultraviolet-C (250 nm) to shortwave-infrared (1250 nm) range is essential and desirable for various applications such as optical communication, spectral switching, and memory storage. We have utilized ultraviolet-responsive gallium nitride (GaN) and Tin selenide (SnSe) as the infrared-activated material to fabricate a broadband heterojunction-based optical detector. Through SnSe/GaN heterostructure, the fabricated detector combines GaN's ultraviolet to visible, with SnSe's visible to shortwave-infrared detectability. The device also possesses great responsiveness and a low dark current due to edge contact geometry, which directly accesses the heterostructure interface for both materials. The fabricated device functions well from the ultraviolet-C to the shortwave-infrared region, exhibiting the highest responsivity of 128 AW-1 and the lowest noise equivalent power of 5.2 × 10−14 WHz−1/2, the quantum efficiency ∼5 × 104% with a response time ∼800 μs for ultraviolet illumination while the highest responsivity of 6.06 AW-1 and noise equivalent power of 1 × 10−12 WHz−1 for the device under infrared illumination. The research will open up new possibilities for optoelectronic applications utilizing heterostructure-based wideband detection.

One-step solvothermal synthesis of heterostructured nanocomposite Ni0.85Se/MnSe as the high-performance electrode material for supercapacitors

A facile one-step solvothermal method is developed to prepare heterostructured nanocomposite Ni0.85Se/MnSe. High-resolution transmission microscopy confirms the formation of the heterostructure. When coated onto carbon cloth and used as the electrode material for supercapacitors, the electrode with the optimized Ni0.85Se/MnSe exhibits specific capacity of 1118 C g−1 at the current density of 1 A g−1, and a capacity retention at 83.2% after 5000 charge-discharge cycles at 10 A g−1 in 4 M KOH using three-electrode system. The assembled asymmetric supercapacitor exhibits the specific energy of 49.3 Wh kg−1 at the power density of 799.81 W kg−1, and 97.8% of the initial capacity is retained after 5000 charge-discharge cycles at 5 A g−1. Kinetic study indicates that the major contribution of the capacity is the diffusion-controlled process, and the electrode exhibits battery-type behavior. The excellent charge storage performance is originated from the higher number of electrochemically active sites, improved reaction kinetics and facilitated diffusion that are induced by the charge redistribution at the heterostructure interface. Conversion of the surface metal selenides to oxides and (oxy)hydroxides is observed during the long-term charge-discharge cycling. The heterostructured nanocomposite Ni0.85Se/MnSe is a promising candidate as the electrode material for supercapacitors.

Theoretical Investigation of Origin of Quantized Conduction in 2D Layered Ruddleson–Popper Perovskite Heterostructure for the RRAM Applications

Quantized conduction achieved in layered materials offers a wide range of applications in electronics. A comprehensive analysis of electronic properties of Sr2ZrO4/TiN- and Sr2ZrO4/TaN-layered heterostructure is carried out using plane wave-based first principles calculations. To understand the origin of quantized conduction, the role of oxygen vacancies (Vos) in 2D layered Ruddleson–Popper perovskite (Sr2ZrO4) is analyzed using density of states, isosurface, and integrated charge density plots. The origin of quantized states formed near the Fermi level is proposed in terms of charge conduction layer formed at the interface. The comprehensive insight of Sr2ZrO4/TiN and Sr2ZrO4/TaN heterostructure interface is provided by shedding light on the charge redistribution from charge density and Bader charge analysis. Meanwhile, work function is calculated for the confirmation of charge conducting behavior of the two layered heterostructures. The interface of these two layered heterostructures revealed the quantized conduction phenomena which cannot be achieved with either layer alone. Stable switching achieved withaTaN electrode being an important task for robust RS and solving sneak path related problem is opening roadmap for 2D layered RRAM devices.

Modulating Hydrogen Adsorption via Charge Transfer at the Semiconductor-Metal Heterointerfacefor Highly Efficient Hydrogen Evolution Catalysis.

Designing and synthesizing highly efficient and stable electrocatalysts for hydrogen evolution reaction (HER) is important for realizing the hydrogen economy. Tuning the electronic structure of the electrocatalysts is essential to achieve optimal HER activity, and interfacial engineering is an effective strategy to induce electron transfer in a heterostructure interface to optimize HER kinetics. In this study, ultrafine RhP2 /Rh nanoparticles are synthesized with a well-defined semiconductor-metal heterointerface embedded in N,P co-doped graphene (RhP2 /Rh@NPG) via a one-step pyrolysis. RhP2 /Rh@NPG exhibits outstanding HER performances under all pH conditions. Electrochemical characterization and first principles density functional theory calculations reveal that the RhP2 /Rh heterointerface induces electron transfer from metallic Rh to semiconductive RhP2 , which increases the electron density on the Rh atoms in RhP2 and weakens the hydrogen adsorption on RhP2 , thereby accelerating the HER kinetics. Moreover, the interfacial electron transfer activates the dual-site synergistic effect of Rh and P of RhP2 in neutral and alkaline environments, thereby promoting reorganization of interfacial water molecules for faster HER kinetics.

Inheritable Organic‐Inorganic Hybrid Interfaces with π–d Electron Coupling for Robust Electrocatalytic Hydrogen Evolution at High‐Current‐Densities

AbstractRational heterointerface engineering is crucial for superior and robust hydrogen evolution reaction (HER). Herein, a delicate organic‐inorganic hybrid heterojunction based on the assembly of oxalate with polyaniline (PANI) for HER at high‐current‐densities is envisioned. Strong π–d electron coupling is achieved between the delocalized π electrons of PANI and the localized d electrons of oxalate metal sites. The CoC2O4 nanosheets are grown on nickel foam (NF) with Ni2+ ions substitution by the precursor etching. By virtue of the synergy of hetero ions and π–d electron coupling, metal sites obtain sufficient exposure and electronic structure optimization. Surprisingly, the phase transition of oxalate during HER in the alkaline environment does not weaken the π–d electronic coupling of the organic‐inorganic hybrid interfaces. Inheritable interfacial electron interaction provides a reliable guarantee for robust stability at high‐current‐densities while endowing the hybrid materials with extremely low overpotentials. As expected, post‐phase reconstructed Co0.59Ni0.41(OH)2@PANI/NF displays impressive HER activity, with a low overpotential of 43 mV@−10 mA cm−2 and robust stability at −1000 mA cm−2 for 30 h in the alkaline environment. This study sheds light on the rational heterostructure interface design and promotes the architecture of an impressive electrocatalysts system.

Construction of heterostructure interface with FeNi2S4 and CoFe nanowires as an efficient bifunctional electrocatalyst for overall water splitting and urea electrolysis

The design of high-performance non-noble-metal-based electrocatalysts for electrooxidation reactions involving splitting of water molecule for energy and environmental applications is the need of the hour. In this study, we report the electrocatalytic performance of a nanocomposite catalyst of FeNi2S4 nanoparticles/CoFe nanowires supported on nickel foam that was prepared by a simple hydrothermal method. The electrocatalyst has several advantages, such as the nanocomposite structure, relatively high electrical conductivity, and synergistic effect between FeNi2S4 and CoFe. These characteristics enhanced the catalytic efficiency of FeNi2S4/CoFe electrode, gaining small overpotentials of 380 and 207 mV for oxygen and hydrogen evolution reactions, respectively, at a current density of 100 mA cm−2. The charge transfer processes are significantly improved by the electron pairs from FeNi2S4 and CoFe, as well as by the enhanced active sites at the electrode-electrolyte interface and their bonding interactions. The electrooxidation of urea was also explored, which showed a lower overpotential of 230 mV to reach 100 mA cm−2 current density. Interestingly, FeNi2S4/CoFe was successfully employed as cathode and anode for urea-assisted water electrolysis, utilizing 1.56 V to produce 10 mA cm−2 current density, which is approximately 160 mV below that for water electrolysis, thus verifying the lower energy consumption during electrolysis. These results indicate that nanoparticle and nanowire composite catalysts can be used for wastewater treatment and green energy production applications.

Rational design of double perovskite La2Ni0.5Co0.5MnO6 decorated polyaniline array on MoO3 nanobelts with strong heterointerface boosting oxygen evolution reaction and urea oxidation

The design and implementation of affordable high-performance electrocatalysts for the oxygen evolution reaction (OER) and urea electrooxidation reaction (UOR) are critical for clean and environmentally friendly energy conversion. Herein, we constructed a novel heterostructure interface engineering of double perovskite La2Ni0.5Co0.5MnO6 (LNCM) nanoparticles and MoO3 nanobelt array-supported amorphous polyaniline (PANI; MoO3/P) for high-performance OER and UOR. Structural and morphological analyses confirmed the formation of a heterostructure interface. The optimized La2Ni0.5Co0.5MnO6@MoO3/P (LMP-30) demonstrated electrocatalytic performance with low overpotentials of 300 mV at 10 mA cm−2 (vs RHE) for OER and 0.48 V at 50 mA cm−2 (vs Hg/HgO) for UOR, as well as better stability after testing for 12 h. The improved electrocatalytic performance was attributed to its distinctive hierarchical nanostructure, which had a synergistic effect on modulating the electrical characteristics and an electrochemically active surface area. More importantly, the LNCM nanoparticles on the surface of MoO3/P nanobelts can potentially provide more electrocatalytic active sites, excellent charge transport capacity, enhanced electrical properties, and strong electronic contacts between MoO3/P and LNCM.

Coaxial electrospinning synthesis of size-tunable CuO/NiO hollow heterostructured nanofibers: Towards detection of glucose level in human serum

Nanofibers (NFs) have found wide applications by virtue of their particular morphology and high specific surface area. In this study, size-tunable hollow CuO/NiO NFs were synthesized by coaxial electrospinning and subsequent calcination. The synthesized hollow CuO/NiO NFs owned large specific surface area for catalytic active sites. In addition, the formation of heterostructure interface between CuO and NiO was beneficial to improve the electrocatalytic performance. As non-enzymatic electrode material, the synthesized CuO/NiO NFs exhibited superior electrocatalytic capability for glucose oxidation. When the molar ratio of CuO to NiO is 0.4, the composite NFs achieved the optimal electrocatalytic ability for glucose oxidation, performing high sensitivity of 1324.17 μA mM−1 cm−2 and wide liner range from 1 to 10,000 μM. The constructed electrode has been utilized to detect glucose concentration in real serum with excellent recovery, indicating that CuO/NiO hollow heterostructured NFs are promising materials for biomedical applications.

A thermoregulating separator based on black phosphorus/MOFs heterostructure for thermo-stable lithium-sulfur batteries

Apart from the traditional problems of shuttling effect of polysulfides and unmanageable growth of lithium dendrites, lithium-sulfur batteries (LSBs) could also unavoidably undergo drastic changes in internal temperature for high-rate charging/discharging process, which could shorten the cycle lifespan of the batteries. Herein, a novel asymmetric thermoregulating separator based on MOFs/black phosphorus heterostructure (UiO66@BP) was developed to address the issues above-mentioned effectively. The asymmetric separator was fabricated by encapsulating the phase-change material of paraffin wax (PW) in polyacrylonitrile nanofibers followed by vacuum filtration of UiO66@BP hybrids onto the surface of the electrospun separator. The block-adsorb-catalyze process of polysulfides in UiO66@BP heterostructure interface contributed to the smooth and effective conversion of the captive polysulfides, therefore the cell exhibited ultralow fading rate of 0.016% per cycle over 1000 cycles, which was comparable to other relative reports of Li-S cells. Moreover, the thermoregulating separator could alleviate the internal temperature rise timely since the melting process of PW could absorb large amounts of heat. The experimental results also showed that the heat absorption and preservation properties of the encapsulated PW endowed the separator with good performance in temperature adjustment, therefore the cells presented smooth and stable cycling stability as well as stable coulomb efficiency compared to none PW-based separator. This work proposed a new insight of phase-change material-based separator contributing to stable solid electrolyte interface and cycling stability of the battery in temperature-varying condition, anticipating its promising application in stable and long-life cycles Li-S batteries.

Elucidating the Synergic Effect in Nanoscale MoS2 /TiO2 Heterointerface for Na-Ion Storage.

Interface engineering in electrode materials is an attractive strategy for enhancing charge storage, enabling fast kinetics, and improving cycling stability for energy storage systems. Nevertheless, the performance improvement is usually ambiguously ascribed to the "synergetic effect", the fundamental understanding toward the effect of the interface at molecular level in composite materials remains elusive. In this work, a well-defined nanoscale MoS2 /TiO2 interface is rationally designed by immobilizing TiO2 nanocrystals on MoS2 nanosheets. The role of heterostructure interface between TiO2 and MoS2 by operando synchrotron X-ray diffraction (sXRD), solid-state nuclear magnetic resonance, and density functional theory calculations is investigated. It is found that the existence of a hetero-interfacial electric field can promote charge transfer kinetics. Based on operando sXRD, it is revealed that the heterostructure follows a solid-solution reaction mechanism with small volume changes during cycling. As such, the electrode demonstrates ultrafast Na+ ions storage of 300 mAh g-1 at 10 A g-1 and excellent reversible capacity of 540 mAh g-1 at 0.2 A g-1 . This work provides significant insights into understanding of heterostructure interface at molecular level, which suggests new strategies for creating unconventional nanocomposite electrode materials for energy storage systems.

100% N2O inhibition in photocatalytic NOx reduction by carbon particles over Bi2WO6/TiO2 Z-scheme heterojunctions

The chemically inert property of nitrous oxide (N2O) has made it difficult to be reduced to benign dinitrogen during (photo) selective catalytic reduction (SCR) of NOx. The introduction of oxygen vacancies and BrØnsted acid sites to thermal catalysts is found to effectively inhibit N2O formation. However, the efficiency is still far from satisfactory and the inhibition of N2O in photocatalytic selective reduction of NOx has not been investigated yet. Herein, 100% inhibition of N2O formation during photo-SCR of NOx with carbon particles is successfully achieved via the fabrication of Bi2WO6/TiO2 Z-scheme heterojunction photocatalyst. The completely inhibited N2O formation is attributed to the rapid charge separation and stronger N2O adsorption on the (101) plane of TiO2 according to the density functional theory calculations and experimental results. The presence of water vapor prolongs the reaction time for NOx photo-reduction of carbon particles but has no significant effect on carbon oxidation rate. Introduction of heterostructure interface effectively accelerates photo-induced charge carrier separation and transfer, thereby enhancing photocatalytic efficiency for NOx reduction with carbon particles. The optimized 0.2 Bi2WO6/TiO2 (molar ratio) composite achieves the highest formal electron/photon quantum efficiency of 0.036, which is 3.3 times that of TiO2. The results provide an alternative perspective on the catalyst fabrication via the simple heterojunction materials for toxic byproduct control in the field of pollutants removal.

Effect of novel La-based alloy modification on hydrogen storage performance of magnesium hydride: First-principles calculation and experimental investigation

LaNi4.5X0.5(X = Fe, Co, Al, Ni) alloys are prepared and doped into MgH2 by ball milling to enhance the hydrogen storage performance, respectively. Both hydrogenation & dehydrogenation kinetics are experimentally measured, and the results indicate that LaNi4.5Fe0.5 doped MgH2 exhibits the top H2 absorption/desorption performance compared with other samples. It is worth noting that the optimal doping amount of LaNi4.5Fe0.5 is selected as 15 wt.% combined with the consideration of working temperature and H2 storage capacity. More importantly, the as-prepared MgH2-15 wt.%LaNi4.5Fe0.5 sample may rapidly introduce the equivalent H2 within 1000 s at mild temperature and pressure of 200 °C and 1 MPa, and it is completely impossible for MgH2 to occur any hydrogenation under this operation conditions. Moreover, the activation energy barriers for hydrogenation & dehydrogenation decline by 62.90% & 20.75% respectively, suggesting the successful doping and property of La-based alloy inside MgH2 as expected. In addition, a variety of as-prepared alloys are experimentally compared and discussed, and the related the heterostructure interface, electronic structure and the formation energy of H vacancy are carried out based on the first-principles calculation, which confirm that LaNi4.5Fe0.5 owns the most favorable catalytic modification effect on Mg-based material.

Boosting the solar conversion efficiency of MoSe2/PtX2 (X = O, S) vdW heterostructure by strain and electric field engineering

Vertically stacking two-dimensional materials via weak van der Waals (vdW) forces is an effective strategy for modulating optoelectronic performance of materials. To accelerate more novel MoSe2-based heterostructure design, the interlayer coupling effect in MoSe2/PtX2 (X = O, S) heterostructure has been systematically studied, from the atomic structure to the electronic and optical properties, on the basis of first-principles calculations and BSE model with scissor inclusion. Density functional theory (DFT) calculations unveil a type-II indirect bandgap measuring between 0.85 and 0.91 eV at HSE06 level, with Bader and charge density difference analyses suggesting occurrence of charge redistributions at the interface and electrons diffusion from MoSe2 to PtX2 layers, driven by large band offsets. The thermodynamic and thermal stabilities of the heterostructures are demonstrated by the negative binding energy and AIMD simulation. The heterostructure interface is influenced by the weak vdW coupling with an equilibrium interlayer distance of 3.01 to 3.08 Å and binding energy of −5.5 to −11.2 meV Å−2, indicating an exothermic process and steady adhesion at the interface. Reasonable lattice mismatch that ranges from 1.5 to 4.7% between the vdW heterostructure and separate monolayers suggests good structure compatibility. The optical performance of the heterostructure was examined using the real and imaginary components of dielectric function, where enhanced light absorption of 104–105 cm−1 and prominent peaks are observed encompassing the infrared to ultraviolet domains. Record high spectroscopic limited maximum efficiency (SLME) of ∼33% was also predicted. The absorption strength of MoSe2/PtO2 and MoSe2/PtS2 enhances with increasing negative external electric field (Eext) and compressive strain, individually, inferring their optical properties modulation by Eext and biaxial strain. Both heterostructures present high carrier mobility up to 1322.98 cm2 V−1 s−1 in zigzag direction.

Efficient removal of 2-chloroethyl ethyl sulfide in solution under solar light by magnesium oxide-decorated polymeric carbon nitride photocatalysts and mechanism investigation

• CN/MgO heterostructure was prepared by thermal exfoliation followed by precipitation. • Rich N defects and O dopants boosted photo-activity of CN/MgO with high surface area. • A built-in electric field at the interface spatially separated electron-hole pairs. • CN/MgO degraded 99% CEES within 120 min under visible light and ambient conditions. • CN/MgO detoxified CEES with good selectivity to non-toxic sulfoxide in solution. Removing hazardous chemicals such as chemical warfare agents is crucial for the environment, defense, and public security. Herein, magnesium oxide-decorated carbon nitride photocatalysts (CN/MgO) were fabricated for detoxification of 2-chloroethyl ethyl sulfide (CEES) in solutions under the irradiation of a solar simulator. CN/MgO samples were prepared via thermal exfoliation followed by precipitation. The surface enhancements of as-prepared photocatalyst, such as high specific surface area, rich-nitrogen defects, and oxygen dopants, improved adsorption capacity, reaction active sites, and localized charge distribution. CN/MgO catalyst showed high performance of detoxification of CEES in solutions (99% of 200 parts per million volume (ppmv) hydroxylethyl ethyl sulfide, a hydrolysis product of CEES, within 120 min). In addition, the detoxification in chloroform solution was conducted to elucidate the hydrolysis effect in the solution phase. Density functional theory calculations revealed that a built-in electric field at the heterostructure interface could facilitate spatial separation of photo-excited electron-hole pairs. Scavenger tests proved that superoxide radicals contributed to good photo-oxidation reactivity. The reaction mechanism was suggested using the results with GC-MS, XPS, FTIR, and XRD. The as-prepared photocatalyst could function under ambient conditions without adding any base or acid. The detoxification exhibited good selectivity to transfer CEES to sulfoxide, avoiding over-oxidation to generate toxic sulfone.

Inducing the SnO2-based electron transport layer into NiFe LDH/NF as efficient catalyst for OER and methanol oxidation reaction

• Introduce the electron transport layer SnO 2 between NiFe LDH and conductive substrate NF was first reported. • SnO 2 nanosheets are interwoven to form a sponge-like 3D structure, which promotes the formation of relatively smaller and thinner NiFe LDH nanosheets, thereby generating more active sites and reducing electron transmission resistance. • It was verified that the electronic structure of Ni and Fe was optimizing via the introduction of SnO 2 . • NiFe LDH@SnO 2 /NF possesses a low overpotential of 234 mV at 10 mA cm −2 for OER and 1.396 V at 10 mA cm −2 for methanol oxidation reaction. In an electrocatalyst with a heterointerface structure, the different interfaces can efficiently adjust the catalyst's conductivity and electron arrangement, thereby enhancing the activity of the electrocatalyst. Ultrathin and smaller NiFe LDH was successfully constructed on the surface of SnO 2 nanosheet supported NF by layer by layer assembly, and exhibits lower overpotential of 234 mV at a current density of 10 mA cm −2 , which only increases by 6.4% even at a high current density of 100 mA cm −2 . The excellent OER activity of catalyst is attributed to the contribution of the semiconductor SnO 2 electron transport layer. Through experiments and characterization, 3d structure SnO 2 nanosheets control the growth of ultra-thin nickel-iron, the hierarchical interface between SnO 2 and NiFe LDH can change the electron arrangement around the iron and nickel active centers at the interface, resulting the valence states of iron slightly increased and Ni 3+ content increased. The result will promote the oxidation of water. Meanwhile, the SnO 2 semiconductor as electron transport layer is conducive to trapping electrons generated in oxidation reaction, promoting electrons transferring from the NiFe LDH active center to the Ni substrate more quickly, and enhance the activity of NiFe LDH. It also shows excellent activity in an electrolyte solution containing 0.5 M methanol and 1 M KOH, and only 1.396 V (vs. RHE) is required to drive a current density of 10 mA cm −2 .