2D/2D g‑C₃N₄/MnO₂ Nanocomposite as a Direct Z‑Scheme Photocatalyst for Enhanced Photocatalytic Activity

Constructing two-dimensional (2D) composites using layered materials is considered to be an effective approach to achieve high-efficiency photocatalysts. Herein, a 2D/2D g-C₃N₄/MnO₂ heterostructured photocatalyst was synthesized via in situ growth of MnO₂ nanosheets on the surface of g-C₃N₄ nanolayers using a wet-chemical method. The hybrid nanomaterial was characterized by a range of techniques to study its micromorphology, structure, chemical composition/states, and so on. The g-C₃N₄/MnO₂ nanocomposite exhibited greatly improved photocatalytic activities for dye degradation and phenol removal in comparison to the single g-C₃N₄ or MnO₂ component. On the basis of the electron paramagnetic resonance spectra, X-ray photoelectron spectra, and the Mott–Schottky measurements, we consider that a Z-scheme heterojunction was generated between the g-C₃N₄ nanosheets and MnO₂ nanosheets, wherein the photoinduced electrons in MnO₂ combined with the holes in g-C₃N₄, leading to enhanced charge carrier extraction and utilization upon photoexcitation. This work provides an effective approach to construct the 2D/2D heterojunctions for the application in solar-to-fuel conversion and photocatalytic water treatment

MoSe₂ Nanosheet Array with Layered MoS₂ Heterostructures for Superior Hydrogen Evolution and Lithium Storage Performance

Engineering heterostructures of transition metal disulfides through low-cost and high-yield methods instead of using conventional deposition techniques still have great challenges. Herein, we present a conveniently operated and low-energy-consumption solution-processed strategy for the preparation of heterostructures of MoSe₂ nanosheet array on layered MoS₂, among which the two-dimensional MoS₂ surface is uniformly covered with high-density arrays of vertically aligned MoSe₂. The unique compositional and structural features of the MoS₂–MoSe₂ heterostructures not only provide more exposed active sites for sequent electrochemical process, but also facilitate the ion transfer due to the open porous space within the nanosheet array serving as well-defined ionic reservoirs. As a proof of concept, the MoS₂–MoSe₂ heterostructures serve as promising bifunctional electrodes for both energy conversions and storages, which exhibit an active and acid-stable activity for catalyzing the hydrogen evolution reaction, high specific capacity of 728 F g^–1 at 0.1 A g^–1, and excellent durability with a remained capacity as high as 676 mA h g^–1 after 200 cycles

Upconversion-Agent Induced Improvement of g‑C₃N₄ Photocatalyst under Visible Light

Herein, we report the use of upconversion agents to modify graphite carbon nitride (g-C₃N₄) by direct thermal condensation of a mixture of ErCl₃·6H₂O and the supramolecular precursor cyanuric acid-melamine. We show the enhancement of g-C₃N₄ photoactivity after Er³⁺ doping by monitoring the photodegradation of Rhodamine B dye under visible light. The contribution of the upconversion agent is demonstrated by measurements using only a red laser. The Er³⁺ doping alters both the electronic and the chemical properties of g-C₃N₄. The Er³⁺ doping reduces emission intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes

Liquid-Based Growth of Polymeric Carbon Nitride Layers and Their Use in a Mesostructured Polymer Solar Cell with <i>V</i>_oc Exceeding 1 V

Herein we report a general liquid-mediated pathway for the growth of continuous polymeric carbon nitride (C₃N₄) thin films. The deposition method consists of the use of supramolecular complexes that transform to the liquid state before direct thermal condensation into C₃N₄ solid films. The resulting films exhibit continuous porous C₃N₄ networks on various substrates. Moreover, the optical absorption can be easily tuned to cover the solar spectrum by the insertion of an additional molecule into the starting complex. The strength of the deposition method is demonstrated by the use of the C₃N₄ layer as the electron acceptor in a polymer solar cell that exhibits a remarkable open-circuit voltage exceeding 1 V. The easy, safe, and direct synthesis of carbon nitride in a continuous layered architecture on different functional substrates opens new possibilities for the fabrication of many energy-related devices

Large-Scale Silver Sulfide Nanomesh Membranes with Ultrahigh Flexibility

The growth of flexible semiconductor thin films and membranes is highly desirable for the fabrication of next-generation wearable devices. In this work, we have developed a one-step, surface tension-driven method for facile and scalable growth of silver sulfide (Ag2S) membranes with a nanomesh structure. The nanomesh membrane can in principle reach infinite size but only limited by the reactor size, while the thickness is self-limited to ca. 50 nm. In particular, the membrane can be continuously regenerated at the water surface after being transferred for mechanical and electronic tests. The free-standing membrane demonstrates exceptional flexibility and strength, resulting from the nanomesh structure and the intrinsic plasticity of the Ag2S ligaments, as revealed by robust manipulation, nanoindentation tests and a pseudo-in situ tensile test under scanning electron microscope. Bendable electronic resistance-switching devices are fabricated based on the nanomesh membrane

Large-Scale Silver Sulfide Nanomesh Membranes with Ultrahigh Flexibility

The growth of flexible semiconductor thin films and membranes is highly desirable for the fabrication of next-generation wearable devices. In this work, we have developed a one-step, surface tension-driven method for facile and scalable growth of silver sulfide (Ag2S) membranes with a nanomesh structure. The nanomesh membrane can in principle reach infinite size but only limited by the reactor size, while the thickness is self-limited to ca. 50 nm. In particular, the membrane can be continuously regenerated at the water surface after being transferred for mechanical and electronic tests. The free-standing membrane demonstrates exceptional flexibility and strength, resulting from the nanomesh structure and the intrinsic plasticity of the Ag2S ligaments, as revealed by robust manipulation, nanoindentation tests and a pseudo-in situ tensile test under scanning electron microscope. Bendable electronic resistance-switching devices are fabricated based on the nanomesh membrane

Hierarchical Nanostructures of Nitrogen-Doped Porous Carbon Polyhedrons Confined in Carbon Nanosheets for High-Performance Supercapacitors

Interconnected close-packed nitrogen-doped porous carbon polyhedrons (NCPs) confined in two-dimensional carbon nanosheets (CNSs) have been prepared through a sustainable one-pot pyrolysis of a simple solid mixture of zeolitic imidazolate framework-8 (ZIF-8) crystals and with organic potassium as the precursors. The hierarchically organized framework of the NCP–CNS composites enables NCPs and CNSs to act as well-defined electrolyte reservoirs and mechanical buffers accommodating large volume expansions of NCPs, respectively. Among the unique composite nanostructures, the NCPs with vast micropores provide electric double-layer capacitances, while the CNSs bridge the individual NCPs to form a conductive pathway with a hierarchical porosity. As a result, the NCP–CNS composites with high electrical integrity and structural stability are used as electrode materials for high-performance supercapacitors, which exhibit excellent electrochemical capacitive characteristics in terms of an outstanding capacitance of 300 F g^–1 at 1 A g^–1, large energy density of 20.9 W h kg^–1, and great cycling performance of 100% retention after 6000 cycles. This work therefore presents a one-pot and efficient strategy to prepare an ordered arrangement of ZIF-8-derived porous carbons toward new electrode materials in promising energy storage systems

Deterministic Nucleation of InP on Metal Foils with the Thin-Film Vapor–Liquid–Solid Growth Mode

A method for growth of ultralarge grain (>100 μm) semiconductor thin-films on nonepitaxial substrates was developed via the thin-film vapor–liquid–solid growth mode. The resulting polycrystalline films exhibit similar optoelectronic quality as their single-crystal counterparts. Here, deterministic control of nucleation sites is presented by substrate engineering, enabling user-tuned internuclei spacing of up to ∼1 mm. Besides examining the theory associated with the nucleation process, this work presents an important advance toward controlled growth of high quality semiconductor thin films with unprecedented grain sizes on nonepitaxial substrates