MoS2/NiS heterostructure grown on Nickel Foam as highly efficient bifunctional electrocatalyst for overall water splitting

It is great important to develop and explore a non-precious bifunctional electrocatalyst with high efficiency and good stability for Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER) in alkaline electrolyte. Herein, a three-dimensional (3D) needle-like MoS₂/NiS heterostructure supported on Nickel Foam (NF) (MoS₂/NiS/NF) is synthesized by a simple hydrothermal method for the first time, which can act as a good bifunctional electrocatalyst for overall water splitting. As expected, the optimal MoS₂/NiS/NF exhibits excellent catalytic performance with a low overpotential of 87 and 216 mV at 10 mA cm⁻² for HER and OER in 1 M KOH electrolyte, respectively, accompanied by good cycle stability. Furthermore, the MoS₂/NiS/NF as bifunctional electrocatalyst in an electrolyzer shows high efficiency with a cell voltage of 1.5 V at 10 mA cm⁻², as well as superior durability. The present work may open a new direction to design and develop a non-precious bifunctional electrocatalyst with excellent catalytic activity for water splitting in the future.     

Biaxial CdTe/CaF2 films growth on amorphous surface

A continuous and highly biaxially textured CdTe film was grown by metal organic chemical vapor deposition on an amorphous substrate using biaxial CaF₂ nanorods as a buffer layer. The interface between the CdTe film and CaF₂ nanorods and the morphology of the CdTe film were studied by transmission electron microscopy (TEM) and scanning electron microscopy. Both the TEM and X-ray pole figure analysis clearly reveal that the crystalline orientation of the continuous CdTe film followed the {111}<121> biaxial texture of the CaF₂ nanorods. A high density of twin faults was observed in the CdTe film. Furthermore, the near surface texture of the CdTe thin film was investigated by reflection high-energy electron diffraction (RHEED) and RHEED surface pole figure analysis. Twinning was also observed from the RHEED surface pole figure analysis.     

Si diffusion in magnetron sputtered silicon carbide films deposited on silicon and carbon substrates

Self-diffusion of silicon in magnetron sputtered silicon carbide films deposited on different substrates (crystalline silicon and glassy carbon) is investigated. Since crystallization of amorphous silicon carbide films strongly depends on the substrate, the diffusivity of silicon is expected to depend on the substrate as well. Isotope hetero-structures and secondary ion mass spectrometry were used for analysis. For amorphous samples an upper limit of the diffusivity of 1 × 10^− 21 m²/s is derived at 1100 C°. For crystallized films diffusivities between 1350 °C and 1600 °C are found to be not significantly different for the two types of substrates. For samples deposited on glassy carbon substrates an activation enthalpy ΔH_D = (8.7 ± 0.9) eV was found for the self-diffusion of Si. The consequences of our findings for crystallization are discussed.     

调制掺杂AlxGa1-xN/GaN异质结磁输运研究

通过低温和高磁场下的磁输运测量,首次在Ａｌ０．２２Ｇａ０．７８Ｎ／ＧａＮ异质结中观察到了舒勃尼科夫－德哈斯振荡的双周期特性,发现在Ａｌ０．２２Ｇａ０．７８Ｎ／ＧａＮ异质结的三角势阱中产生了二维电子气（２ＤＥＧ）的第二子带占据,发生第二子带占据的阈值２ＤＥＧ浓度估算为７．２＊１０＾１２ｃｍ＾－２,在阈值２ＤＥＧ浓度下第一子带和第二子带能级的距离计算为７５ｍｅＶ。     

Carbon nanotube-based heterostructures for high-performance photodetectors: Recent progress and future prospects

Unique optical, electrical and chemical properties make carbon nanotubes (CNTs) an excellent candidate for potential applications in the next-generation optoelectronics. Especially, the optoelectronic properties of CNTs can be enhanced dramatically by constructing heterostructures with other materials, in which the charge separation efficiency is enhanced and the recombination probability of excitons is suppressed significantly. Therefore, the CNT-based heterostructures have been widely used as active materials in high-performance photoelectronic devices. Herein, the recent progress of the CNT-based heterostructure photodetectors is reviewed. Firstly, the working mechanisms and typical figures-of-merits are introduced. Secondly, different type CNT-based heterostructures and related photodetectors are highlighted, such as van der Waals heterostructures, all-carbon heterostructures, and bulk heterostructures. Finally, we give the current challenges and future prospects for the development of this emerging field.     

Three-dimensional ZnCo/MoS2–Co3S4/NF heterostructure supported on nickel foam as highly efficient catalyst for hydrogen evolution reaction

Exploring inexpensive and earth-abundant electrocatalysts for hydrogen evolution reactions is crucial in electrochemical sustainable chemistry field. In this work, a high-efficiency and inexpensive non-noble metal catalysts as alternatives to hydrogen evolution reaction (HER) was designed by one-step hydrothermal and two-step electrodeposition method. The as-prepared catalyst is composed of the synergistic MoS₂–Co₃S₄ layer decorated by ZnCo layered double hydroxides (ZnCo-LDH), which forms a multi-layer heterostructure (ZnCo/MoS₂–Co₃S₄/NF). The synthesized ZnCo/MoS₂–Co₃S₄/NF exhibits a small overpotential of 31 mV and a low Tafel plot of 53.13 mV dec^?1 at a current density of 10 mA cm^?2, which is close to the HER performance of the overpotential (26 mV) of Pt/C/NF. The synthesized ZnCo/MoS₂–Co₃S₄/NF also has good stability in alkaline solution. The excellent electrochemical performance of ZnCo/MoS₂–Co₃S₄/NF electrode originates from its abundant active sites and good electronic conductivity brought by the multilayer heterostructure. This work provides a simple and feasible way to design alkaline HER electrocatalysts by growing heterostructures on macroscopic substrates.     

Ag@AgCl quantum dots embedded on Sn3O4 nanosheets towards synergistic 3D flower-like heterostructured microspheres for efficient visible-light photocatalysis

Taking advantage of the oil-water interface, we introduced Ag@AgCl quantum dots (QDs) onto 2D Sn₃O₄ nanosheets to fabricate a composite photocatalyst with a 3D flower-like structure (denoted as Ag@AgCl/Sn₃O₄). Using the degradation of tetracycline hydrochloride (TC-HCl) and methylene blue (MB) as the examples, the as-prepared Ag@AgCl/Sn₃O₄ composite with Ag@AgCl weight loading of 1% indicated 9.6 and 7.88 times higher photocatalytic activity than the Sn₃O₄ nanosheets. Within both degradation reactions, hydroxyl radicals (•OH) and superoxide radicals (•O²⁻) were identified as the critical oxidation intermediates based on radical trapping and electron spin resonance (ESR) experiments. The unique morphology and photoelectrochemical properties of the as-prepared composites suggested the introduced Ag@AgCl QDs cooperated with the Sn₃O₄ semiconductor to enhance the utilization of solar energy. Overall, the established heterojunction helped to reduce the transfer barrier of the photoinduced charge carriers, wherein the surface plasmonic resonance (SPR) of Ag nanoparticles was believed to take the main responsibility. The present work combines the Ag@AgCl-QDs and flower-like 3D Sn₃O₄ microspheres for the first time to achieve an impressive degrading rate of TC-HCl and MB at the Ag@AgCl weight loading as low as 1%.     

Enhanced photoelectrochemical performance based on conformal and uniform ZnO/ZnSe/CdSe heterostructures on Zn foil substrate

The erosion issue of ZnO nanorod arrays (NRAs) film is the major obstacle in surface sensitization of ZnO NRAs grown on Zn foil substrate for photoelectrochemical (PEC) applications. In this paper, PEC performance of ZnO NRAs grown on Zn foil substrate was greatly enhanced by coating ZnSe and CdSe on the surface of ZnO NRAs. Dense ZnO NRAs were in-situ grown on seed-free Zn foil substrate in a NH₃·H₂O and NaOH hydrothermal system. ZnSe/CdSe co-sensitized ZnO heterostructures were then successfully synthesized using ZnO NRAs as precursors by two successive in-situ ion exchanges without damaging Zn foil and ZnO NRAs film. To obtain optimal photoconversion efficiency, anion exchange time and temperature were optimized. ZnO/ZnSe/CdSe heterostructures with optimized structure were shown as a layer of compact ZnSe/CdSe nanofilm conformally and uniformly coated on ZnO NRAs, which leads to efficient separation of photogenerated carriers, significant enhancement in visible-light absorption, and excellent PEC performance with photocurrent density of 3.008 mA/cm² (−0.2 V vs. Ag/AgCl) and photoconversion efficiency of 1.99% (0.418 V vs. RHE in polysulfide electrolyte solution), 27.55 and 40.61 times higher than those of ZnO NRAs, respectively.     

B-implantation and Annealing for SiGe Epilayers

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