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The current limited and uneven distribution of lithium resources has stimulated strong motivation to develop new rechargeable batteries that use alternative charge carriers. Potassium‐based batteries are promising candidates for future large‐scale energy storage due to their low cost and high operating voltage. Here for the first time, a rechargeable K/Br battery is reported, which is assembled with a hollow carbon spheres cathode, a K metal anode, and a SOBr2 electrolyte containing AlBr3 and potassium bis‐(fluorosulfonyl)imide. The in situ formed crystalline KBr protective film during discharging plays a significant role in this system. The redox reaction between the KBr film and liquid Br2 at the cathode contributes to the main reversible capacity. K/Br battery exhibits high capacity (up to 400 mAh g‐1) and constant operating voltage (at 3.72 V vs K+/K). As a proof of concept, the K/Br battery demonstrated in this work points to a new pathway for low‐cost and next‐generation rechargeable batteries. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) is a promising photocatalytic material for use in environmental protection and water splitting. However, its short photogenerated carrier lifetime and narrow visible-light response restrict its extensive application. Herein, a novel electrospinning method was developed to prepare bismuth (Bi)-modified BiVO4 (Bi/BiVO4) porous nanofibers. The morphologies, structures, and chemical states of the obtained samples were characterized using a series of analytical techniques. The photocatalytic performance of the Bi/BiVO4 porous nanofibers was evaluated via the photocatalytic degradation of methylene blue (MB) under visible-light irradiation. The enhanced visible-light photocatalytic activity of Bi/BiVO4 can be attributed to the Bi nanoparticles, which exhibit a surface plasmon resonance (SPR) effect and have semiconductor character, extending the optical absorption of BiVO4 and restraining the recombination of electron–hole pairs during the photocatalytic degradation process, respectively. In this work, new insight is provided into the fabrication of a Bi/BiVO4 composite, which can act as an outstanding visible-light responsive photocatalyst, facilitating its application in the field of environmental protection. [ABSTRACT FROM AUTHOR]

Ceramic matrix nanocomposites containing graphene possess superior mechanical properties. However, these nanocomposites are very difficult to be prepared using the conventional methods due to severe grain growth and simultaneous degradation of the graphene at high sintering temperatures and long dwell time. Herein, the dense ZrO2/rGO (reduced graphene oxide) nanocomposites are successfully fabricated by flash sintering of the green compacts consisting of ZrO2 nanoparticles and graphene oxide (GO) at 893–951℃ in merely 5 seconds under the alternating current (AC) electric fields of 130–150 V cm−1. The GO can be in situ thermal reduced during the flash sintering. The as‐prepared ZrO2/rGO nanocomposites exhibit excellent mechanical properties. This study presents a green and simple approach to fabricate the dense ceramic matrix nanocomposites reinforced with graphene at low temperatures in a short time. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) nanosheets are promising candidates as earth-abundant and low-cost catalyst for hydrogen evolution reaction (HER). Nevertheless, compared with the benchmark Pt/C catalyst, the application of MoS2 nanosheets is limited to its relatively low catalytic activity, especially in alkaline environments. Here, we developed a dual-cation doping strategy to improve the alkaline HER performance of MoS2 nanosheets. The designed Ni, Co co-doped MoS2 nanosheets can promote the tandem HER steps simultaneously, thus leading to a much enhanced catalytic activity in alkaline solution. Density functional theory calculations revealed the individual roles of Ni and Co dopants in the catalytic process. The doped Ni is uncovered to be the active site for the initial water-cleaving step, while the Co dopant is conducive to the H desorbing by regulating the electronic structure of neighboring edge-S in MoS2. The synergistic effect resulted by the dual-cation doping thus facilitates the tandem HER steps, providing an effective route to raise the catalytic performance of MoS2 materials in alkaline solution. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new acetylenic carbon material called pyridyne, which is composed of acetylenic linkages and pyridine rings. From first-principles calculations, we investigate the structural, elastic and electronic properties of pyridyne. It is found that the structure of pyridyne is stable at 300 K and its stability is comparable to experimentally synthesized graphdiyne and graphtetrayne. Compared with graphene or graphyne, pyridyne possesses more diverse pores and reduced delocalization of electrons. The in-plane stiffness of pyridyne is 183 N m−1 with a Poisson's ratio of 0.304. Pyridyne is found to be a semiconductor with a direct band gap of 0.91 eV. The intrinsic electron mobility can reach 6.08 × 104 cm2 V−1 s−1, while the hole mobility can reach 1.82 × 104 cm2 V−1 s−1. [ABSTRACT FROM AUTHOR]

Ni-based heterostructures have been regarded as promising catalysts for the hydrogen evolution reaction (HER) in alkaline solutions due to its high efficiency in catalyzing the water dissociation process. Therefore, an in-depth understanding of the water-dissociation-related activity of Ni species within varied structures and coordination environments is significant for the design of novel catalysts. Herein, we synthesized three types of Ni-based heterostructures, namely NiS/MoS2, NiSe/MoS2 and NiSe2/MoS2 by a controllable route to investigate their catalytic trends and origins of the HER under alkaline conditions. Combined with experimental data and theoretical calculation results, we revealed that the alkaline HER activity of the heterostructures relies on the catalyzing ability of Ni species in the Volmer step, which is associated with the d-band center, and is further related to the coordination condition of the Ni atoms in the chalcogenides. With the highest valence state and d-band center among the samples, Ni atoms in NiS exhibit the fastest reaction rate in the Volmer step, thus providing the best catalytic activity for the NiS/MoS2 heterostructure in the alkaline HER. Furthermore, an activity trend for the Ni chalcogenides in the Volmer step, in the order of NiS > NiSe2 > NiSe, has been proposed, which is expected to contribute insights into the design of novel heterostructured catalysts. [ABSTRACT FROM AUTHOR]

To develop new phosphor materials for optical temperature sensing application, a series of Yb3+-Tb3+ and Eu3+ doped Ca2Gd8(SiO4)6O2 (CGS) phosphors were designed by solid-state reaction method. Upon 980 nm excitation, the green emission of Tb3+ was observed in the CGS:0.8Yb3+, xTb3+ (0.08 ≤ x ≤ 1.2) phosphors, which could be mainly owing to the cooperative energy transfer from Yb3+ to Tb3+. The corresponding upconversion (UC) luminescence mechanism was studied by using the dependence of UC emission intensity on excitation powder. The temperature-dependence indicates that the ratio of the Tb3+ emission intensities of I5D4 and I5D3 changes with temperature, which shows a linear relationship. The high absolute sensitivity was achieved to be about 0.431 K−1. Upon 463 nm excitation, the Eu3+ 5D0,1-7FJ transitions were found in the Eu3+-activated CGS. The investigation on temperature-dependence reveals that with increasing temperature the intensities of 5D0-7FJ transitions decrease but those of 5D1-7FJ transitions increase gradually, owing to the thermally coupled 5D0 and 5D1 levels. The fluorescence lifetime based temperature sensing properties was studied in this sample. [ABSTRACT FROM AUTHOR]

A phosphate based composite ceramics system, (1 − x)SrZn(PO)- xTiO (0 ≤ x ≤ 0.5), was prepared by the solid-state reaction method, and the relations between the phase composition, crystal structure and microwave dielectric properties were investigated. The results show that only two phases of SrZn(PO) and TiO can be obtained in the whole range of x value, and high relative density can be archived for all compositions as suitable sintering temperatures were applied. In the variation process of phase composition ratio, lower increase of dielectric constant value (<14) and wide changing range of temperature coefficient of resonant frequency (from −76 to +110 ppm/°C) can be obtained synchronously. When the phase composition ratio x value are 0.5, composite ceramics above possesses microwave dielectric properties as ε = 12.011, Q × f = 24900 GHz and τ = +91 ppm/°C as the sintering temperature was 1000 °C. [ABSTRACT FROM AUTHOR]

Water-soluble carbon dots (CDs) have been successfully synthesized by green-one-pot hydrothermal method. The CDs with small particle size exhibit fairly good water solubility, tunable photoluminescence, up-converted photoluminescence, and low toxicity. What is more, the as-prepared CDs were successfully applied in the field of cell image. [ABSTRACT FROM AUTHOR]

Carbon quantum dots/TiO2 nanotubes composites were prepared by a simple technical route through which TiO2 nanotubes prepared by electrospinning were dispersed in carbon quantum dots solution, and dried at 80 °C. The results indicated that the TiO2 nanotubes composites were combined with the carbon quantum dots. The photocatalytic activity of the carbon quantum dots/TiO2 nanotubes composites was investigated by the degradation of rhodamine B under visible light irradiation, and it was demonstrated to be significantly enhanced compared with that of pure TiO2 nanotubes. Through analysis, this enhancement of visible light photocatalytic activity was attributed to the carbon quantum dots with the unique up-converted photoluminescence behavior. [ABSTRACT FROM AUTHOR]

Abstract: Highly Photoluminescent (PL) carbon dots (CDs) with a PL quantum yield (PLQY) of 7.7% have been prepared from cornflour by a simple hydrothermal method. The as-prepared carbon dots have good water solubility, well distributed particle size, amorphous structure and acceptable fluorescence lifetime. Besides, due to the fairly good biocompatibility and outstanding fluorescent properties, the CDs were successfully applied to cell imaging and Cu2+ detecting. [Copyright &y& Elsevier]

Water-soluble, fluorescent carbon dots (CDs) have been successfully synthesized from waste paper. The as-prepared CDs, with an amorphous structure and small particle size, exhibit good photostability, high photoluminescence quantum yields (PLQYs) and fairly low toxicity, which indicate potential applications in the field of biolabelling. [ABSTRACT FROM AUTHOR]

Highly photoluminescent ZnSe/Au nanocomposites have been prepared via a simple low-temperature-aqueous synthesis and direct coupling approach. The mechanism of surface plasmons enhanced photoluminescence of ZnSe/Au nanocomposites is investigated. Furthermore, due to high photostability and biocompatibility, the as-prepared ZnSe/Au nanocomposites are demonstrated as excellent probes in cellular imaging. [ABSTRACT FROM AUTHOR]

Antiperovskite CuNFe3 (CNF) thin films have been successfully prepared by chemical solution deposition (CSD) for the first time. They are versatile in many applications as an iron-based nitride. The preparation of pure CNF thin films is a challenging work for the complexity of the phase diagram. Herein, the CNF thin films are phase-pure and polycrystalline. Annealing temperature effects on the microstructures and physical properties were investigated, showing that the CNF thin films are metallic and can be considered as a candidate for room temperature soft-magnets with a large saturated magnetization (Ms) and a low coercive field (Hc). At high temperatures, the electrical transport behavior of CNF thin films presents a low temperature coefficient of resistivity (TCR) value, while the electron–electron interaction is prominent at low temperatures. The reported solution methods of CNF thin films will enable extensive fundamental investigation of the microstructures and properties as well as provide an effective route to prepare other antiperovskite transition-metal nitride thin films. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a half-cell reaction in water electrolysis for producing hydrogen gas. In industrial water electrolysis, the HER is often conducted in alkaline media to achieve higher stability of the electrode materials. However, the kinetics of the HER in alkaline medium is slow relative to that in acid because of the low concentration of protons in the former. Under the latter conditions, the entire HER process will require additional effort to obtain protons by water dissociation near or on the catalyst surface. Heterostructured catalysts, with fascinating synergistic effects derived from their heterogeneous interfaces, can provide multiple functional sites for the overall reaction process. At present, the activity of the most active known heterostructured catalysts surpasses (platinum-based heterostructures) or approaches (noble-metal-free heterostructures) that of the commercial Pt/C catalyst under alkaline conditions, demonstrating an infusive potential to break through the bottlenecks. This review summarizes the most representative and recent heterostructured HER catalysts for alkaline medium. The basics and principles of the HER under alkaline conditions are first introduced, followed by a discussion of the latest advances in heterostructured catalysts with/without noble-metal-based heterostructures. Special focus is placed on approaches for enhancing the reaction rate by accelerating the Volmer step. This review aims to provide an overview of the current developments in alkaline HER catalysts, as well as the design principles for the future development of heterostructured nano- or micro-sized electrocatalysts. [ABSTRACT FROM AUTHOR]

Foam-like three dimensional mesoporous NiO on Ni foam was fabricated via facile hydrothermal etching and subsequent annealing treatment. The porous NiO consists of a large number of nanosheets with mean thickness about 50 nm, among which a large number of mesoscopic pores with size ranges from 100 nm to 1 μm distribute. The electrochemical performance of the as-prepared NiO-Ni as anode for lithium ion battery was studied by conventional charge/discharge test, which shows excellent cycle stability and rate capability. It exhibits initial discharge and charge capacities of 979 and 707 mA h g −1 at a charge/discharge rate of 0.7 C, which maintain of 747 and 738 mA h g −1 after 100 cycles. Even after 60 cycles at various rates from 0.06 to 14 C, the 10th discharge and charge capacities of the NiO-Ni electrode can revert to 699 and 683 mA h g −1 when lowering the charge/discharge rate to 0.06 C. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of g-C 3 N 4 /ZnIn 2 S 4 composites were prepared by simple two-step methods. • The photocatalytic tendency of CN/ZIS samples shows "M" type with the increase of CN. • A relative p-n junction can be constructed after the combination of CN and ZIS samples. • This work mainly studies the migration direction of the photogenerated carriers. Semiconductor photocatalysis as an alternative technology has received extensive attention for addressing the worldwide energy and environment issues. However, it is still a great challenge and imperative to profoundly understand the migration mechanisms for achieving the complete utilization of photoexcited charge carriers. In this paper, a series of g-C 3 N 4 /ZnIn 2 S 4 heterojunction composites were fabricated by thermal polycondensation and solvothermal methods and then thoroughly characterized by a range of techniques. Photocatalytic selective oxidation of aromatic alcohols to corresponding aldehydes with O 2 under visible light irradiation was introduced as a model reaction system to evaluate the photocatalytic performance of the as-prepared samples. The results exhibit that when the main constituent of photocatalyst is ZnIn 2 S 4 , the transfer of the photogenerated charge carriers adopts a band-band mechanism in g-C 3 N 4 /ZnIn 2 S 4 heterojunction composite. However, when the main constituent of photocatalyst is g-C 3 N 4 , the transfer of the photogenerated charge carriers adopts a Z-scheme mechanism. Therefore, the different compositions of the composite samples lead to the different electronic conductivities and then affect the direction of the built-in electric field in the relative p-n junction, finally causing the different transfer mechanisms of the photogenerated charge carriers for g-C 3 N 4 /ZnIn 2 S 4 composite samples. [ABSTRACT FROM AUTHOR]

Searching for a cost-effective, high efficient and stable bifunctional electrocatalyst for overall water-splitting is critical to renewable energy systems. In this study, three-dimensional (3D) curved nanosheets of Mo-doped Ni 3 S 2 grown on nickel foam were successfully synthesized via a one-step hydrothermal process. The hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) in alkaline environment of this 3D catalyst are investigated in detail. The results show that it possesses lower overpotential, high current densities and small Tafel slopes both in OER and HER. For HER, the catalysts show excellent electrochemical performance, demonstrating a low over-potential of 212 mV at 10 mA cm −2 with a large decrease of 127 mV compared to the undoped Ni 3 S 2 . And it also shows a lower overpotential of 260 mV at 10 mA cm −2 which decreases 30 mV for OER. In addition, it is only need 1.67 V for the overall water splitting at 10 mA cm −2 which is 70 mV. It found that the Mo element would change the morphology of Ni 3 S 2 and induce much more active sites for HER and OER. The as-prepared Mo-doped Ni 3 S 2 bi-functional electrocatalyst could act as the promising electrode materials for water splitting. [ABSTRACT FROM AUTHOR]

Abstract: A low-temperature hydrothermal method was developed to synthesize urchinlike γ-MnO2 nanostructures. Time-dependent evolutions of morphology and crystallinity were investigated to explore the growth mechanism of the γ-MnO2 urchins. The results show that the growth process of the γ-MnO2 urchins occurs in two main stages, which are the generation of γ-MnO2 microspheres and the following epitaxial growth of γ-MnO2 nanoneedles on the surface of the initial microspheres. Microwave absorption properties of the urchinlike γ-MnO2 nanostructures were studied in terms of complex permittivity and permeability. An effective absorption bandwidth (reflection loss lower than −10dB) of 8.8GHz was achieved from the γ-MnO2/paraffin wax composite. [Copyright &y& Elsevier]

Inexpensive metal-based electrocatalyst with excellent stability and activity for efficient hydrogen evolution reaction is the most critical issue for large-scaled water splitting. However, the electricity kinetics in alkaline is relatively sluggish than in acid owing to the concentration of protons in alkaline is low. Thus, accurate structural designs to obtain more protons in the water dissociation on the surface of catalyst are necessary. In this work, a defect-rich MoP is encapsulated with carbon shell, which precisely regulated to distinguish the affection on hydrogen evolution reaction. The synergistic effect between carbon shell and defective sites is identified by the free energy and charge distribution density for water/hydrogen adsorption in hydrogen evolution via a density functional theory calculation. The results show that the lattice defects and the carbon shells play a unique role in enhancing catalytic performance, which the lattice defects decide the active sites and the thinner carbon shell would enhance its activity. The optimal overpotential in alkaline media of this designed MoP/C is 100 mV at 10 mA cm−2, its Tafel slope is 67.4 mV dec−1, and also exhibits a long-term stability for 12 h. • Structure disordering and carbon shell on MoP precisely regulated. • Low onset overpotential (30 mV), small Tafel slope (67.4 mV·dec−1) can achieved in alkaline media. • Synergistic effect between lattice defects and carbon shell are considered to enhance HER catalytic performance. [ABSTRACT FROM AUTHOR]