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Silicon nitride (Si3N4) has great potential for applications in photoelectric and semiconductor fields. In this study, a novel strategy of fabricating Si3N4 crystals is reported, and the morphology of α-Si3N4 can be controlled. The aBN/SiO2/Si wafers were designed and irradiated by a high-energy electron beam for 2 min using home-made equipment. Tree-like α-Si3N4 dendrites and [001]-oriented unbranched α-Si3N4 whiskers can be synthesized by controlling the electron beam energy. Related formation mechanisms were analyzed based on componential and structural characterization using a scanning electron microscope and high-resolution transmission electron microscope. In addition, photoluminescence measurements indicate that the synthesized α-Si3N4 exhibit unique photoluminescence properties. This is attributed to α-Si3N4 forming abundant Si–Si bonds, Si dangling bonds, N dangling bonds and oxygen bonds in the synthesis process. These findings provide new insights into fabricating high-quality Si3N4 crystals, as well as developing related high-performance micro- or nano-devices. [ABSTRACT FROM AUTHOR]

A highly stable new structural phase of monoelemental two-dimensional boron sheet has been discovered. Such new material was acquired by removing the metal atom layers from the quasi-layered boride material AlMgB14, inspired by the top-down synthesis of MXenes, which includes the direct etching and exfoliation of the bulk MAX phase. It has been shown that this structure possesses distinct stability over other two-dimensional boron phases, which is caused by the B–B single bonds that connect B12 clusters and three-coordinate boron atoms, instead of the universally existing three-center two-electron B–B bonds. This new structure has proved to be a direct narrow bandgap semiconductor with intermediate bands and favorable for metal cation and hydrogen molecule adsorption. Specifically, this new structure exhibits particularly high specific capacities as anodes for various metal ion batteries. The findings indicate that this new structure of two-dimensional boron has great potential in the energy fields, such as high-efficiency solar cells, energy storage devices and hydrogen storage substrates. [ABSTRACT FROM AUTHOR]

A Mn/Co dual nanoparticle-decorated hierarchical carbon structure was derived from a Zn/Mn/Co/chitosan composite hydrogel. This strategy critically relied on the formation of a supramolecularly crosslinked hydrogel that allowed the efficient and homogeneous incorporation of highly active Mn/Co species onto the surface of hierarchical carbon structures. The resultant electrocatalyst outperformed Pt/C toward the oxygen reduction reaction in 0.1 M KOH electrolytes. [ABSTRACT FROM AUTHOR]

Engineering nanoarray structures with favorable hydrophilicity is proposed to unlock the electrocatalysis of NiFe2O4 for the oxygen evolution reaction (OER). The resulting electrode, consisting of NiFe2O4 nanospindles directly grown on FeNi3 foam, features enlarged active surface area, high hydrophilicity and increased electronic conductivity, which achieves superior OER activity and remarkable durability. [ABSTRACT FROM AUTHOR]

A novel photocatalyst-free visible-light-mediated dithioacetalization of aldehydes and thiols has been developed. This protocol is operationally simple, mild and atom-economical, which provides an environmental benign access to dithioacetals at room temperature under aerobic conditions. [ABSTRACT FROM AUTHOR]

Harvesting energy from environmental moisture is a promising technique for sustainable electric power resource. Herein, a new scalable fabrication method for flexible moisture-electric energy transformation device by dispersing or direct printing carbon dots (CDs) on paper is reported. A facile strategy for self-establishing ionic gradient on both sides of the device by constructing an asymmetric structure (the side of device is encapsulated) is proposed, which avoids prior processing of the materials for building asymmetric functional groups. The carboxyl groups on CDs near the open side of the device ionize more protons than that near the closed side, resulting in a potential drop across the device due to the concentration difference of the released protons on the two sides. The device can produce a sustainable voltage of −40 mV for over 100 min at a fixed humidity value. In addition, the device responds to direct touching of a finger or human exhalation, thus indicating its great potential for applications in electronic skins and humidity sensors. [ABSTRACT FROM AUTHOR]

Hierarchical materials are a favourite for energy storage/harvesting technologies, such as supercapacitors and electrically-driven hydrogen production. In this work, we report a robust and highly active nanomaterial for pseudocapacitors and hydrogen production by growing vanadium pentoxide on the surface of nickel sulfide (denoted as V2O5@Ni3S2). V2O5@Ni3S2 shows a capacitance of up to 854 F g−1 at a current density of 1 A g−1 and good rate capability. The capacitance can retain ca. 60% of the initial specific capacitance even after 1000 cycles at a current density of 1 A g−1. For the hydrogen evolution reaction (HER), the overpotential of V2O5@Ni3S2 is around 95 mV at 10 mA cm−2. The excellent electrochemical performance of the V2O5@Ni3S2 hybrid is attributed to the synergistic effect between vanadium pentoxide and nickel sulfide for pseudocapacitors, and the V2O5@Ni3S2 interface and V–S active bonding in the hierarchical structure for the HER. This work demonstrates an effective structure design for supercapacitors with high energy density and for efficient hydrogen production with high catalytic activity by incorporating metal oxide with metal sulfide. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting is an environmentally friendly technique for hydrogen production. In this work, we report a novel photocatalyst consisting of two-dimensional (2D) titanium carbide (Ti2C) and graphitic carbon nitride (g-C3N4). We observe substantially enhanced water splitting activities due to the efficient synergistic interaction between Ti2C and g-C3N4. Optimal properties are achieved in the g-C3N4 with a loading of 0.4 wt% Ti2C with a hydrogen production rate of 47.5 μmol h−1, which is 14.4 times as much as that in the case using pure g-C3N4, and it even outperforms Pt-loaded g-C3N4. We further show that the Ti2C/g-C3N4 has high stability and good reproducibility. We expect that the Ti2C/g-C3N4 can be a photocatalyst for large scale applications because both Ti2C and g-C3N4 are low-cost, abundant, and nontoxic. [ABSTRACT FROM AUTHOR]

It is a great challenge to explore cheap, abundant and eco-friendly electrocatalysts for hydrogen evolution reaction (HER). Here, we report the fabrication of VS2 nanoflowers with 1T phase by a simple hydrothermal method and their electrocatalytic performance in the HER. We find that the VS2 nanoflowers show comparable HER performance to Pt in acids, including an ultra-low onset potential of 32 mV, a Tafel slope of 34 mV dec−1 which resembles that of Pt, and a small overpotential of 58 mV (54 mV for Pt) at a current density of 10 mA cm−2. High stability and almost 100% faradaic efficiency indicate the practical application of VS2 nanoflowers in the HER. Our first-principles calculations reveal that the thermoneutral Gibbs free energy of hydrogen adsorption on both the basal and edge sites of the 1T-VS2 monolayer can be achieved under certain hydrogen coverage and the monolayer shows good conductivity, which contribute to the impressive catalytic performance of VS2 nanoflowers. We expect that the VS2 nanostructures may be applicable in electrocatalysis with high efficiency. [ABSTRACT FROM AUTHOR]

A novel hollow-structured CuO derived from chitosan-coated Cu/Cu2O composite hollow spheres was mass produced via a supramolecular hydrogel templating method and homogeneously co-doped with C and N. Evaluation of the as-produced co-doped CuO hollow spheres as anode materials for Li ion batteries showed that they had superior electrochemical properties. [ABSTRACT FROM AUTHOR]

A biopolymer-chitosan based Supramolecular Hydrogel type solid state Electrolyte (SHE) is prepared via a simple and fast cross-linking between chitosan and Li+/Ag+. The obtained SHE itself shows high thermal stability and excellent flexible and mouldable properties. When integrated in an asymmetric supercapacitor with MnO2 as the positive electrode and active carbon as the negative electrode, it can survive more than 10 000 cycles with the areal capacity of 10 mF cm−2 at the 1.8 mA cm−2 current density. [ABSTRACT FROM AUTHOR]