Heterostructure Interface Research Articles

Na0.6Co3O4- La/Pr co-Doped Ceria as Semiconductor-Ionic Heterostructure Material for Fuel Cell Application

Abstract Functional Sodium-doped cobalt oxide (Na0.6Co3O4, NCO) was incorporated to regulate and improve the electrochemical performance of La/Pr co-doped ceria (LCP) electrolytic materials with good operative stability, forming an p-n heterostructure electrolyte (LCP-NCO) for low-temperature solid oxide fuel cell (LTSOFC) application. LCP-NCO is a new potential semiconductor-ionic material, achieving a maximum power density of 1075 mW cm-2 along with a high open-circuit voltage of 1.061 V at 520℃. Scanning electron microscopy combined with transmission electron microscopy unveiled the crystallographic microstructure of heterostructure interface between LCP and NCO. Raman spectra and Fourier transform infrared spectroscopy spectra were analyzed to distinguish the functional groups and the vibrational properties. Ultraviolet–visible absorption and ultraviolet photoelectron spectroscopy have determined the accurate band edge positions of LCP and NCO and p-n heterojunction nature. Built-in electric field in semiconductor heterostructure and more oxygen vacancies created through the variation of Co3+/Co2+ ratio in LCP-NCO during the fuel cell test, contributed to the enhanced ionic transport. Characteristic of competent conductivity of 0.26-0.42 S cm-1 at 400-520℃, and the improved cell duration, revealed that the LCP-NCO as a hybrid oxygen ion and protonic conductor would be a potential electrolyte for LTSOFC.

Strain-Induced Self-Assembly at Interface of Two-Dimensional Heterostructures Boosts CO2 Reduction to Methanol by H2O.

CO2 conversion with pure H2O into CH3OH and O2 driven by solar energy can supply fuels and life-essential substances for extraterrestrial exploration. However, the effective production of CH3OH is significantly challenging. Here we report an organozinc complex/MoS2 heterostructure linked by well-defined zinc-sulfur covalent bonds derived by the structural deformation and intensive coupling of dx2-y2(Zn)-p(S) orbitals at the interface, resulting in distinctive charge transfer behaviors and excellent redox capabilities as revealed by experimental characterizations and first-principle calculations. The synthesis strategy is further generalized to more organometallic compounds, achieving various heterostructures for CO2 photoreduction. The optimal catalyst delivers a promising CH3OH yield of 2.57 mmol gcat-1 h-1 and selectivity of more than 99.5%. The reverse water gas shift mechanism is identified for methanol formation. Meanwhile, energy-unfavorable adsorption of methanol on MoS2, where the photogenerated holes accumulate, ensures the selective oxidation of water over methanol.

Modulating Interfacial Charge Transfer Behavior through the Construction of a Hetero-Interface for Efficient Photoelectrochemical Water Splitting

Surface-coupled transition metal oxyhydroxide (TMOOH) on semiconductor (SC)-based photoanodes are effective strategies for improving photoelectrochemical (PEC) performance. However, there is a substantial difference between the current density and theoretical value due to the inevitable interfacial charge recombination of SC/TMOOH. Here, we employ BiVO4/FeNiOOH as a model, constructing the BiVO4/MnOx/CoOx/FeNiOOH integrated system by introducing a novel hetero-interface regulation unit, i.e., MnOx/CoOx. As expected, the optimized integrated system demonstrates a photocurrent density as high as 5.0 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (RHE) under 1 sun AM 1.5G illumination, accompanied by 12-h stability. The detailed electrochemical analysis and intensity modulated photocurrent spectroscopy (IMPS) have confirmed that the high PEC performance mainly originates from the hetero-interface structure, which not only suppresses the interfacial charge recombination by accelerating the photogenerated hole transfer kinetics from BiVO4 to FeNiOOH but promotes the kinetics of surface oxygen evolution reaction (OER). Notably, these findings can also be extended to other structures (CeOx/CoOx), reflecting its universality. This finding has provided a new insight into the highly efficient solar energy conversion in the SC/TMOOH system.

Spatiotemporal evolution of ultrafast photocarrier dynamics across WS2-ReS2 lateral interface.

2D lateral heterostructures possess atomically sharp lateral interfaces, while understanding of their ultrafast photocarrier dynamics from a spatiotemporal viewpoint is rather elusive. In this study, we have investigated the spatiotemporal evolution of photocarrier dynamics across the 1D lateral interface of a WS2-ReS2 2D lateral heterostructure utilizing femtosecond laser pump-probe. The nontrivial band offset across the 1D lateral interface markedly mediates the spatiotemporal photocarrier transfer and transport processes. Subsequently, a hole accumulation region on the WS2 side and an electron accumulation region (1DEG) on the ReS2 side have been spatially identified by correlating ultrafast photocarrier signals. The measured width of the unilateral depletion region is 1360 ± 160nm. Our work has provided substantial insights into mediated photocarrier dynamics in the 2D lateral heterostructure, which will benefit explorations in 2D interfacial physics and 2D lateral optoelectronic devices.

Interfacial Bonding Induced Charge Transfer in Two-dimensional Amorphous MoO3-x/Graphdiyne Oxide Non-van der Waals Heterostructures for Dominant SERS Enhancement.

Two-dimensional semiconductor-based nanomaterials have shown to be an effective substrate for Surface-enhanced Raman Scattering (SERS) spectroscopy. However, the enhancement factor (EF) tends to be relatively weak compared to that of noble metals and does not allow for trace detection of molecules. In this work, we report the successful preparation of two-dimensional (2D) amorphous non-van der Waals heterostructures MoO3-x/GDYO nanomaterials using supercritical CO2. Due to the synergistic effect of the localized surface plasmon resonance (LSPR) effect and the charge transfer effect, it exhibits excellent SERS performance in the detection of methylene blue (MB) molecules, with a detection limit as low as 10-14M while the enhancement factor (EF) can reach an impressive 2.55 × 1011. More importantly, the chemical bond bridging at the MoO3-x/GDYO heterostructures interface can accelerate the electron transfer between the interfaces, and the large number of defective surface structures on the heterostructures surface facilitates the chemisorption of MB molecules. And the charge recombination lifetime can be proved by a ~1.7-fold increase during their interfacial electron-transfer process for MoO3-x/GDYO@MB mixture, achieving highly sensitive SERS detection.

Interface engineering of three-phase nickel–cobalt sulfide/nickel phosphide/iron phosphide heterostructure for enhanced water splitting and urea electrolysis

Rational designing efficient transition metal-based multifunctional electrocatalysts is highly desirable for improving the efficiency of hydrogen production from water cracking. Herein, a self-supported three-phase heterostructure electrocatalyst of nickel–cobalt sulfide/nickel phosphide/iron phosphide (CoNi5S8-Ni2P-FeP2) was prepared by a two-step gas-phase sulfurization/phosphorization strategy. The heterostructure in CoNi5S8-Ni2P-FeP2 provides a favorable interfacial environment for electron transfer and synergistic interaction of multiphase active components, while the introduced electronegative P/S not only serves as a carrier for proton capture in the hydrogen evolution reaction (HER) process but also promotes the metal-electron outflow, which in turn accelerates the generation of high-valent Ni3+ species to enhance the catalytic activity of oxygen evolution reaction (OER) and urea oxidation reaction (UOR). As expected, CoNi5S8-Ni2P-FeP2 reveals excellent multifunctional electrocatalytic properties. An overpotential of 35/215 mV is required to reach 10 mA cm−2 for HER/OER. More encouragingly, a current of 100 mA cm−2 requires only 1.36 V for UOR with CoNi5S8-Ni2P-FeP2 as anode, which is much lower as compared to the OER (1.50 V). Besides, a two-electrode water/urea electrolyzer assembled based on CoNi5S8-Ni2P-FeP2 has a voltage of only 1.59/1.48 V when the system reaches 50 mA cm−2. This work provides a new idea for the design of energy-efficient water/urea-assisted water-splitting multifunctional catalysts with multi-component heterostructure synergistic interface engineering.

Ultrasensitive ion liquid-CNT vdW heterostructure interface via anion-cation pair switch for SO2 detection

Low dimensional van der Waals (vdW) interface shows great advantages for application in vapor detection, such as ultra-high sensitivity and excellent reversibility. However, detection of non-character REDOX capacity and low atmosphere concentration gas such as SO2 is more challengeable. Inspired by the high efficient gas adsorption performance and versatile ion pair combination of ionic liquids, we constructed a vdW heterostructure interface based polymeric ion liquid/SWCNT sensor with different ionic pairs for SO2 detection. Via the composites tuning of SWCNTs and poly(vinylbenzyl 3-ethylimidazolium)-based ionic liquids (PILs) modified with different anions of chloride (Cl-), boron tetrafluoride (BF4-), hexafluorophosphate (PF6-), and bis(trifluoromethanesulfonimide) ions (Tf2N-), stable vdW heterostructure interface was successfully constructed, as proved by SEM, FTIR, XPS and Raman spectra. Upon SO2 adsorption, the distance between the cation/anion was tuned at the heterostructure interface, which triggered great composite tightness changes and thus electrical signal changes of heterostructure interface due to the reversed electron transfer, proved by XPS, Raman spectra and dynamics simulations. Among the sensors composed of the different anions, PIL-BF4-SWCNT exhibited lowest detection limit 20.4 ppt for SO2, which is the best result ever reported. The sensor also show great selectivity, reversibility and stability, with 3.77% response for 512 ppt SO2 within 14 days. The new strategy will open a new way for selective, ultrasensitive and low power vapor detection in complex environment.

Probing impact on magnetic behavior of cobalt layer grown on thick MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document} layer

Understanding the metal-semiconductor heterostructure interface is crucial for the development of spintronic devices. One of the prospective candidates and extensively studied semiconductors is molybdenum disulfide (MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document}). Herein, utilizing Kerr microscopy, we investigated the impact of thick MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document} on the magnetic properties of the 10 nm Co layer. A comparative study on Co/MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {Co}/\\hbox {MoS}_{2}$$\\end{document} and Co/Si shows that coercivity increased by 77% and the Kerr signal decreased by 26% compared to Co grown on Si substrate. In addition, the Co domain structure significantly changed when grown on MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document}. The plausible reason for the observed magnetic behavior can be that the Co interacts differently at the interface of MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document} as compared to Si. Therefore, our studies investigate the interfacial effect on the magnetic properties of Co grown on thick MoS2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_{2}$$\\end{document} layer. Furthermore, our results will help in developing next-generation spintronic devices.

Ab initio study of quantized conduction mechanism in trilayered heterostructure for scaled down memory device applications

Interface of the layered heterostructure revealing the quantized conductance phenomena which cannot be achieved with either semiconducting layer alone in absence of externally applied electric field has wide range of applications in electronic industry of RRAM devices. A comprehensive analysis of electronic properties of CeO2/Ta2O5/CeO2 trilayered heterostructure has been carried out using first principle calculation employing VASP to explore the state of art of RRAM including barrier height, barrier width, conducting filament width and shape. For better understanding of conduction mechanism involved in RS, the influence of crystalline and amorphous phase of Ta2O5 sandwiched between CeO2 layers is analyzed by potential energy lineups, DOS, isosurface and integrated charge density plots. Origin of quantized states formed near the Fermi level in DOS is provided physically by growth of charge conducting filaments in isosurface charge density plots, and charge redistribution from Bader charge analysis. Outcomes of this study confirmed that with more quantized charge, crystalline Ta2O5 is better for interfacial RRAM devices. Apart from previously available findings, results of this study will provide new route to the potential application of this layered material in electronics especially storage devices.

Optimizing Electron Spin-Polarized States of MoSe2 /Cr2 Se3 Heterojunction-Embedded Carbon Nanospheres for Superior Sodium/Potassium-Ion Battery Performances.

The principal challenges faced by sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) revolve around identifying suitable host materials capable of accommodating metal ions with larger dimensions and addressing the issue of sluggish chemical kinetics. Herein, a MoSe2 /Cr2 Se3 heterojunction uniformly embedded is fabricated in nitrogen-doped hollow carbon nanospheres (MoSe2 /Cr2 Se3 @N-HCSs) as an electrode material for SIBs and KIBs. Cr2 Se3 exhibits spontaneous antiparallel alignment of magnetic moments. Mo2+ doping is employed to regulate the electron spin states of Cr2 Se3 . Moreover, the MoSe2 and Cr2 Se3 heterojunctions induce a lattice mismatch at the heterostructure interface, resulting in spin-polarized states or localized magnetic moments at the interface, potentially contributing to spin-polarized surface capacitance. MoSe2 /Cr2 Se3 @N-HCSs demonstrate a high capacity of 498 mAh g-1 at 0.1 A g-1 with good cycling stability (capacity of 405 mAh g-1 and a coulombic efficiency of 99.8% after 1000 cycles). Additionally, density functional theory (DFT) calculations simulate the accumulation of spin-polarized charges at the MoSe2 /Cr2 Se3 @N-HCSs heterojunction interface, dependent on the surface electron density of the antiferromagnetic Cr2 Se3 and the surface spin polarization near the Fermi level. After regulating the electron spin states through Mo-doping, the band gap of the material decreases. These significant findings provide novel insights into the design and synthesis of electrode materials with exceptional performance characteristics for batteries.

Two-Dimensional SiH/g-C3N4 van der Waals Type-II Heterojunction Photocatalyst: A New Effective and Promising Photocatalytic Material

The two-dimensional layered heterostructure have been demonstrated as an effective method for achieving efficient photocatalytic hydrogen production. In this work, we propose, for the first time, the creation of van der Waals heterostructures from monolayers of SiH and g-C3N4 using first-principle calculations. We also systematically investigated additional properties for the first time, such as the electronic structure and optical behavior of van der Waals heterostructures composed of SiH and g-C3N4 monolayers. The results of this study show that the SiH/g-C3N4 heterostructure is categorized as a type-II heterostructure, which has a bandgap of 2.268 eV. Furthermore, the SiH/g-C3N4 heterostructure interface was observed to efficiently separate and transfer photogenerated charges, resulting in an enhanced photocatalytic redox performance. Moreover, the calculation of HOMO (Highest occupied molecular orbital) and LUMO (Least unoccupied molecular orbital) and charge density difference can further confirm that the SiH/g-C3N4 heterojunction is a type-II heterojunction, which has excellent photocatalytic hydrogen production and water decomposition performance. In addition, the SiH/g-C3N4 heterostructure exhibited excellent HER (Hydrogen evolution reaction) efficiency. This is essential for the process of photocatalytic water splitting. In SiH/g-C3N4 heterojunctions, the redox potential required for water splitting is spanned by the band edge potential. Calculating the absorption spectra, it was discovered that the SiH/g-C3N4 heterostructure possesses outstanding optical properties within the visible-light range, implying its high efficiency in photocatalytic hydrogen production. This research provides a broader research direction for the investigation of novel efficient photocatalysts and offers effective theoretical guidance for future efficient photocatalysts.

Interface engineering of metal sulfides-based composites enables high-performance anode materials for sodium-ion batteries

Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe3N embedded in N-doped carbon nanosheets (SnS/FeS/Fe3N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe3N/NC NSs with abundant heterointerfaces and high conductivity of N-doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe3N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe3N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs.

Decoration of Bi2MoO6 nanosheets with NH2-UiO-66 for boosting visible-light photocatalytic activities

Constructing heterostructured photocatalysts for organic contaminants elimination is promising in the area of environmental purification. For boosting the photocatalytic performance, modulating the heterojunction interface can enhance solar light utilization and facilitate the transporation of photoinduced charge carriers. In this research, octahedral NH2-UiO-66 nanoparticles with large surface area and wide light absorption range were prepared and further employed to in-situ construction of NH2-UiO-66/Bi2MoO6 nanocomposite. The optimized NH2-UiO-66/Bi2MoO6 nanocomposite displays enhanced photocatalytic activities in the elimination of rhodamine B (RhB) and tetracycline (TC). The corresponding degradation rate constant is about 4 and 1.76 times larger than that of individual Bi2MoO6. Combined with the photochemical and electrochemical results, it can be speculated that the higher photocatalytic performance is assigned to the accelerative photoinduced carrier transfer by the formation of well-contacted heterostructured interface. This study provides a theoretical basis for further developing organic–inorganic hybrid catalyst with significant improvement of photocatalytic properties in wastewater treatment.

Auger‐Assisted Secondary Hot Carrier Transfer in a Type I MoS2/PtSe2 Heterostructure

AbstractCharge transfer is vital in determining the optoelectronic properties of atomically thin materials, yet remains elusive in type I heterostructures. Here, distinct two‐step charge transfer processes in a type I MoS2/PtSe2 heterostructure are reported. By exclusively exciting the smaller bandgap PtSe2, strong exciton photobleaching peaks of the larger bandgap MoS2 are observed, indicating primary hot carrier transfer from PtSe2 to MoS2 within 70 fs. More importantly, the amplitude of the exciton peaks shows a secondary increase after the initial rapid decay. These dynamics are distinctly different from the monotonic decrease in monolayer MoS2 and indicate a secondary charge transfer process that is attributed to hot carriers re‐generated in PtSe2 by intralayer Auger recombination. Concurrently, the exciton energy blue shifts within 100 ps, probing the dynamic buildup of a charge‐transfer induced electric field across the heterostructure interface, which displaces electron and hole wavefunctions of MoS2 excitons and reduces the exciton binding energy. The results are corroborated by carrier dynamics and transient absorption spectra simulations by considering the two‐step charge transfer processes. The work reveals Auger‐assisted hot carrier transfer processes in type I heterostructures and suggests the possibility for optoelectronic and photocatalytic applications by optical sub‐bandgap excitation.

Synthesis of NbSe2/Bilayer Nb‐Doped WSe2 Heterostructure from Exfoliated WSe2 Flakes

Forming heterostructures of 2D metals and semiconductors using chemical vapor deposition (CVD) has significant potential to effectively reduce contact resistance in electronic devices. However, semiconducting transition metal dichalcogenide (TMD) layers in metal–semiconductor heterostructures are currently restricted to monolayers despite the superior mobility and density of states in bilayer TMDs. Herein, NbSe2/bilayer Nb‐doped WSe2 metal/semiconductor heterostructure from exfoliated WSe2 flakes are synthesized first. The exfoliated WSe2 bulk crystals on an Nb‐coated substrate are heated to 950 °C under a flow of selenium vapor, and then the NbSe2/bilayer Nb‐doped WSe2 heterostructures are formed. Statistics on the number of Nb‐doped WSe2 layers grown on a 1 cm × 1 cm CVD substrate shows that 65% of the Nb‐doped WSe2 layers are grown as bilayers. X‐ray photoelectron spectroscopy, optical microscopy, and transmission electron microscopy clearly clarify the number of Nb‐doped WSe2 layers and heterostructure of NbSe2/bilayer Nb‐doped WSe2. Electrical measurements using Cr contacts show that bilayer Nb‐doped WSe2 displays 7‐ and 10‐times higher mobility and on/off ratio than monolayer Nb‐doped WSe2. The mobility and on/off ratio are further doubled in NbSe2/bilayer Nb‐doped WSe2 contact compared to Cr/bilayer Nb‐doped WSe2 contact, attributed to a clean interface in vertical stack heterostructure, enhancing electrical performance.

Unveiling the Ultrafast Electron Transfer Dynamics in Epitaxial Dodecahedron CsPbBr3/Au Heterostructure

AbstractEpitaxial perovskite heterostructures consisting noble metal nanoparticles have been received immense interest in hot carrier photovoltaic devices and photocatalysis. The major understanding of carrier extraction across the interface of perovskite heterostructure have shown exciting interest for next generation device applications. In the present study, dodecahedron CsPbBr3/Au heterostructure was synthesized via hot injection method. From HR‐TEM images, we observed direct epitaxial growth between (110) plane of CsPbBr3 and (111) plane of Au nanoparticle (NPs), which was further supported by steady‐state and time‐resolved photoluminescence studies. Further, femtosecond transient absorption spectroscopy has been utilized to understand the charge transfer dynamics of synthesized samples. In CsPbBr3/Au heterostructure, faster recovery has been noticed than that of pristine CsPbBr3, which clearly suggests transfer of electrons from the conduction band of CsPbBr3 to Au NPs. The distinct fast electron transfer in the CsPbBr3/Au heterostructure can be mainly ascribed to the epitaxial growth and strong electronic coupling between CsPbBr3 and Au NPs. The reduced bleach intensity, faster bleach growth and recovery kinetics strongly suggest efficient electron transfer from CsPbBr3 NCs to Au NPs. These findings clearly establish that architecture of metal and perovskite heterostructures may pave way to develop suitable alternative for highly efficient photovoltaic devices and photocatalysis applications.

Tuneable Vertical Hysteresis Loop Shift in Exchange Coupled La0.67Sr0.33MnO3‐SrRuO3 Bilayer

AbstractHarnessing extra degrees of freedom at the heterostructure interface is of crucial importance to bring additional functionalities in modern spintronic devices. Here, a vertical hysteresis loop shift (vertical bias) is demonstrated in an exchange biased system of ferromagnetic thin film heterostructure of La0.67Sr0.33MnO3 (10 nm)‐SrRuO3 (SRO) (20 nm), after field cooling with ±1 T below 100 K close to the Curie temperature (TC) ≈125 K of SRO and loop sweeping under ±1 T field. Besides, a positive exchange bias (HEB) is also observed below TC ≈125 K showing a maximum ≈11 mT at 2 K. The vertical shift is modeled closely using micromagnetic simulations and the layers’ thickness dependency is demonstrated. The reason for the shift is attributed to the simultaneous role of the interfacial antiferromagnetic interaction and the hard anisotropy of SRO against the Zeeman energy. Finally, from the experimental and simulation results, a generalized model of controllable and tunable vertical shift is proposed applicable for other material systems possessing glassy phases, uncompensated/canted spins, absent interfacial exchange coupling, etc., and hence can be informative for the use of vertical shift in future spintronic devices.

Probing the multi-disordered nanoscale alloy at the interface of lateral heterostructure of MoS2–WS2

Abstract Transition metal dichalcogenide (TMDs) heterostructure, particularly the lateral heterostructure of two different TMDs, is gaining attention as ultrathin photonic devices based on the charge transfer (CT) excitons generated at the junction. However, the characteristics of the interface of the lateral heterostructure, determining the electronic band structure and alignment at the heterojunction region, have rarely been studied due to the limited spatial resolution of nondestructive analysis systems. In this study, we investigated the confined phonons resulting from the phonon-disorder scattering process involving multiple disorders at the lateral heterostructure interface of MoS2–WS2 to prove the consequences of disorder-mediated deformation in the band structure. Moreover, we directly observed variations in the metal composition of the multi-disordered nanoscale alloy Mo1−x W x S2, consisting of atomic vacancies, crystal edges, and distinct nanocrystallites. Our findings through tip-enhanced Raman spectroscopy (TERS) imply that a tens of nanometer area of continuous TMDs alloy forms the multi-disordered interface of the lateral heterostructure. The results of this study could present the way for the evaluation of the TMDs lateral heterostructure for excitonic applications.

Ce-doped multi-phase NiMo-based phosphorus/sulfide heterostructure for efficient photo-enhanced overall water splitting at high current densities

NiMo-based electrocatalysts are widely regarded as promising electrocatalysts for overall water splitting (OWS). However, to solve the problem of slow reaction kinetics and serious deactivation at high current density, the reasonable design of NiMo-based electrocatalysts is still a great challenge. In this work, NiMo-based phosphorus/sulfide heterostructure electrocatalysts with different Ce doping ratios (5%/10%/15%Ce-NiMo-PS@NF) have been designed using the combination of cation doping and heterostructure engineering. The doping of Ce not only changes the electronic environment of the heterostructure, accelerates the electron transport at the heterostructure interface, but also enhances the light absorption capacity of the heterostructure. The experimental results show that 10%Ce-NiMo-PS@NF has the best photo-enhanced electrocatalytic activity (hydrogen evolution reaction (HER): η1000 = 250 mV, oxygen evolution reaction (OER): η1000 = 242 mV, and OWS: E1000 = 1.864 V). In addition, its solar-to-hydrogen (STH) efficiency in a photoelectric coupled water splitting system is as high as 18.68%. This study not only provides a new method for the synthesis of new heterostructure electrocatalysts, but also provides a reference for the rational use of light energy to enhance electrocatalytic activity.

Heterostructured Co/CeO2-Decorating N-Doped Porous Carbon Nanocubes as Efficient Sulfur Hosts with Enhanced Rate Capability and Cycling Durability toward Room-Temperature Na-S Batteries.

Room-temperature sodium-sulfur (RT Na-S) batteries have gained significant interest thanks to their satisfactory energy density and abundant earth resources. Nevertheless, practical implementations of RT Na-S batteries are still impeded by serious shuttle effects of sodium polysulfide (NaPS) intermediates, sluggish redox kinetics of cathodes, and poor electronic conductivity from S-species. To solve these problems, heterostructured Co/CeO2-decorating N-doped porous carbon nanocubes (Co/CeO2-NPC) are constructed as a S support, which integrates the strong adsorption and fast conversion of NaPSs, together with superior electronic conductivity. Consequently, the as-synthesized S@Co/CeO2-NPC cathode for RT Na-S batteries exhibits improved rate performance (1275, 561.1, and 485 mAh g-1 at 0.1, 5, and 10 C, respectively) and superior cyclic durability (capacity degeneration of 0.027% per cycle after 1000 cycles at 5 C). Such a S cathode combining a heterostructure interface, hierarchical porous carbon nanocubes, and polar compositions can considerably increase electronic conductivity and promote NaPS adsorption and conversion, achieving superior performance toward RT Na-S batteries.