Topochemical synthesis of Mn2O3/TiO2 and MnTiO3/TiO2 nanocomposites as lithium-ion battery anodes with fast Li+ migration and giant pseudocapacitance via the mesocrystalline effect.

Transition metal compounds are a promising substitute for graphite as lithium-ion battery (LIB) anodes. In this study, mesocrystalline Mn2O3/TiO2 and MnTiO3/TiO2 nanocomposites were synthesized using a layered titanic acid H1.07Ti1.73O4 (HTO) precursor. The ß-MnOOH layer is intercalated into the interlayer of HTO by Mn2+-exchange treatment of H2O2-intercalated HTO, which includes ion-exchange of Mn2+ with H+ in the interlayer and oxidation of Mn2+ to the ß-MnOOH layer by H2O2 in the interlayer space. Mesocrystalline Mn2O3/TiO2 and MnTiO3/TiO2 nanocomposites with a platelike morphology were obtained by heat treatment of a sandwich layered HTO/ß-MnOOH under air and H2/Ar atmospheres, respectively. The electrochemical results suggest that the mesocrystalline Mn2O3/TiO2 and MnTiO3/TiO2 nanocomposites show a synergistic effect for enhanced cycling stability and a mesocrystalline effect for enhanced discharge-charge specific capacity by improving the Li+ mobility and enhancing the pseudocapacitance of the mesocrystalline nanocomposites as LIB anode materials. The discharge-charge specific capacity of the mesocrystalline Mn2O3/TiO2 nanocomposite is twice as high as that of the polycrystalline one caused by the mesocrystalline effect. Furthermore, the synergistic and mesocrystalline effects led to a stable large discharge-charge specific capacity of 710 mA h g-1 for the mesocrystalline Mn2O3/TiO2 nanocomposite. This work proposes a new concept to enhance the performance of anode materials for LIBs using mesocrystalline materials.

Ginger (Zingiber officinale) extract mediated green synthesis of silver nanoparticles and evaluation of their antioxidant activity and potential catalytic reduction activities with Direct Blue 15 or Direct Orange 26.

The green synthesis of silver nanoparticles (AgNPs) using a water extract of Ginger (Zingiber officinale) root by microwave irradiation and its antibacterial activities have been reported. However, AgNPs prepared from different parts of ginger root water or ethanol extract by ultrasound synthesis and their antioxidant activity and whether the biogenic could be used to catalyze the reduction of hazardous dye are unknown. This study concentrated on the facile green synthesis of AgNPs prepared from different parts (unpeeled ginger, peeled ginger, and ginger peel) of ginger root water or ethanol extract by the ultrasound-assisted method. We studied their antioxidant activity and catalytic degradation of hazardous dye Direct Orange 26 (DO26) and Direct Blue 15 (DB15). The surface plasmon resonance (SPR) peak of AgNPs was at 428-443 nm. The biogenic AgNPs were approximately 2 nm in size with a regular spherical shape identified from TEM analysis. The ethanol extracts of dried unpeeled ginger and peeled ginger, fresh peeled ginger and ginger peel. The Z. officinale AgNPs synthesized by dried unpeeled ginger ethanol extract showed the best antioxidant activity. Their scavenging activities were significantly better than BHT (p <0.05). The different parts of ginger extracts showed no catalytic degradation activities of DB15 and DO26. Still, the synthesized Z. officinale AgNPs exhibited good catalytic degradation activities, while their ability to catalytic degradation to DB15 was better than DO26. In the additive ratio of 3 mL DB15, 0.1 mL NaBH4 and 0.1 mL AgNPs, the degradation rates of DB15 (or DO26) at 15 min, 30 min and 60 min were only 1.8% (0.9%), 2.8% (1.4%) and 3.5% (1.6%) in the absence of AgNPs. When adding Z. officinale AgNPs prepared from dried ginger peel ethanol extract or fresh ginger peel water extract, the degradation rates of DB15 sharply increased to 97% and 93% after 30 min, respectively. In conclusion, ginger extract has good antioxidant properties. Z. officinale AgNPs biosynthesis from ginger extract exhibit excellent catalytic degradation activities, especially for the ginger peel extract. They have application value in the treatment of textile effluents and provide a new idea and method for the comprehensive development and utilization of ginger resources.

Controllable preparation of crystalline red phosphorus and its photocatalytic properties.

Single-element phosphorus has received extensive attention in recent years because of its remarkable photocatalytic properties. In the present experiment, amorphous red phosphorus was controllably transformed into [P12(4)]P2[and Hittorf's phosphorus structures by performing bismuth catalysis. The temperature-controllable chemical vapor transport reaction realized the conversion of more than 90% of amorphous red phosphorus to single-phase crystalline red phosphorus. Under very mild ultrasonic treatment, the high-quality [P12(4)]P2[microbelts and Hittorf's phosphorus microrods were stripped into a few layers of nanobelts and sheet-like structures, respectively. As non-metallic catalysts, their rapid photocatalytic degradations of pollutants (methyl orange) and high hydrogen evolution rates revealed the rapid charge transfer and application potential of the crystalline red phosphorus catalyst. The results of this work could provide new ideas for the development of phosphorus-based crystalline photocatalytic systems.

Remarkably enhanced ion-exchange capacity of H2O2-intercalated layered titanate.

H2O2-intercalated layered titanate H1.07Ti1.73O4 (H2O2-HTO) exhibits a dramatically enhanced ion-exchange capacity and remarkably improved reaction rate with various divalent cations. The intercalation can increase the negative charge density of the TiO6 octahedral layer and the number of ion-exchangeable H+ by forming a Ti(iv)-O-O-H bond that is the driving force to change the ion exchange performance.

Enhanced Photovoltaic Performance of BiSCl Solar Cells Through Nanorod Array.

BiSCl single-crystalline nanofibers were synthesized by a facile one-pot solvothermal approach for the first time. BiSCl possesses a double chain type structure and grows readily along the c-axis, resulting the fibrous morphology. UV/Vis absorption spectroscopy revealed that BiSCl nanofibers exhibit a strong light absorption in a wavelength range from UV to visible light, corresponding to a bandgap of 1.96 eV. Ultraviolet photoelectron spectroscopy and density functional theory calculations revealed that BiSCl is a direct n-type semiconductor with valence band maximum and conduction band minimum located at 6.04 and 4.08 eV below the vacuum level, respectively. To investigate the photovoltaic performance, the homogeneous thin film of BiSCl-nanorod array was fabricated on a TiO2 porous film by a modified solvothermal process, where the nanorod array is oriented vertically to the surface of the TiO2 porous film. A proper band alignment of BiSCl-based solar cells with an architecture of fluorine-doped tin oxide (FTO)/TiO2 /BiSCl/(I3 - /I- )/Pt gave a PCE of 1.36 % and a relatively large short-circuit photocurrent density of 9.87 mA cm-2 for the first time. The preliminary photovoltaic study result revealed a potential possibility of BiSCl-nanorod array as a light absorber for solar cells that can be fabricated by the low-cost solution process.

Ferroelectric mesocrystalline BaTiO3/BaBi4Ti4O15 nanocomposite: formation mechanism, nanostructure, and anomalous ferroelectric response.

Ferroelectric mesocrystalline nanocomposites are promising materials for the enhancement of ferroelectricity via lattice strain engineering due to their high density of heteroepitaxial interfaces. In the present study, a ferroelectric mesocrystalline BaTiO3/BaBi4Ti4O15 (BT/BBT) nanocomposite was synthesized using the layered titanate H1.07Ti1.73O4via a facile two-step topochemical process. The BT/BBT nanocomposite is constructed from well-aligned BT and BBT nanocrystals oriented along the [110] and [11-1] crystal-axis directions, respectively. Lattice strain is introduced into the nanocomposite through the formation of a BT/BBT heteroepitaxial interface, which results in a greatly elevated Curie temperature for BBT in the range of 400 °C to 700 °C and an improved piezoelectric response with . In addition, the BT/BBT nanocomposite is stable up to a high temperature of 1100 °C; therefore, mesocrystalline ceramics can be fabricated as high-performance ferroelectric materials.

Introduction of Fe2+ in Fe0.8Ti1.2O40.8- nanosheets via photo reduction and their enhanced electrochemical performance as a lithium ion battery anode.

Fe2+ doped Fe0.8Ti1.2O40.8- nanosheets were firstly utilized as a lithium ion battery anode. The Fe2+ was introduced into the Fe0.8Ti1.2O40.8- nanosheets using a photoreduction method. The introduction of Fe2+ enhanced the electrical conductivity of the material, as well as the specific capacity.

Anomalous piezoelectric response of ferroelectric mesocrystalline BaTiO3/Bi0.5Na0.5TiO3 nanocomposites designed by strain engineering.

Mesocrystals, a new class of unique materials, not only have potential properties based on the individual nanocrystals but also have a single-crystal-like function. Here, we report a ferroelectric mesocrystalline BaTiO3/Bi0.5Na0.5TiO3 (BT/BNT) nanocomposite synthesized from a layered titanate H1.07Ti1.73O4 (HTO) by an ingenious two-step topochemical process for the first time. The BT/BNT nanocomposite is constructed from well-aligned BT and BNT nanocrystals with the same crystal-axis orientation. The BT/BNT heteroepitaxial interface in the nanocomposite is promising for an enhanced piezoelectric performance by using lattice strain engineering, which gives a giant piezoelectric response with a value of 408 pm V-1. The introduced lattice strain at the BT/BNT heteroepitaxial interface causes transitions of pseudo-paraelectric BT and BNT nanocrystals to ferroelectric nanocrystals in the mesocrystalline nanocomposite, which enlarges ferroelectric, piezoelectric and dielectric responses. The lattice strain also results in the elevated Curie temperatures (Tc) of BT and BNT and a new intermediate phase transition.

High Pseudocapacitance in FeOOH/rGO Composites with Superior Performance for High Rate Anode in Li-Ion Battery.

Capacitive storage has been considered as one type of Li-ion storage with fast faradaic surface redox reactions to offer high power density for electrochemical applications. However, it is often limited by low extent of energy contribution during the charge/discharge process, providing insufficient influences to total capacity of Li-ion storage in electrodes. In this work, we demonstrate a pseudocapacitance predominated storage (contributes 82% of the total capacity) from an in-situ pulverization process of FeOOH rods on rGO (reduced graphene oxide) sheets for the first time. Such high extent of pseudocapacitive storage in the FeOOH/rGO electrode achieves high energy density with superior cycling performance over 200 cycles at different current densities (1135 mAh/g at 1 A/g and 783 mAh/g at 5 A/g). It is further revealed that the in-situ pulverization process is essential for the high pseudocapacitance in this electrode, because it not only produces a porous structure for high exposure of tiny FeOOH crystallites to electrolyte but also maintains stable electrochemical contact during ultrahigh rate charge transfer with high energy density in the battery. The utilization of in-situ pulverization in an Fe-based anode to realize high surface pseudocapacitance with superior performance may inspire future design of electrode structures in Li-ion batteries.

Lightweight NiFe2O4 with controllable 3D network structure and enhanced microwave absorbing properties.

3D network structure NiFe2O4 was successfully synthesized by a templated salt precipitation method using PMMA colloid crystal as templates. The morphology, phase composition and microwave absorbing properties of as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vector network analyzer (VNA), and so on. The results revealed that the 3D network structure was configurated with smooth spherical walls composed of NiFe2O4 nanocrystals and their pore diameters being in the range of 80-250 nm. The microwave absorption properties of the 3D network structure NiFe2O4 were crucially determined by the special structure. The synergy of intrinsic magnetic loss of magnetic NiFe2O4 and the interfacial polarization enhanced by 3D network structure and the interaction of multiple mechanisms endowed the sample with the feature of strong absorption, broad bandwidth and lightweight. There is more than one valley in the reflection loss curves and the maximum reflection loss is 27.5 dB with a bandwidth of 4 GHz. Moreover, the 3D network structure NiFe2O4 show a greater reflection loss with the same thickness comparing to the ordinary NiFe2O4 nanoparticles, which could achieve the feature of lightweight of the microwave absorbing materials.

pH-regulated template-free assembly of Sb4O5Cl2 hollow microsphere crystallites with self-narrowed bandgap and optimized photocatalytic performance.

Sb4O5Cl2 hollow microspheres with self-narrowed bandgap and optimized photocatalytic performances are synthesized via a facile template-free method. It is found that the crystal structure and morphology of Sb4O5Cl2 crystallites are strongly dependent on the pH values of precursors. Nano-sized irregular-cuboids assembled Sb4O5Cl2 micro-particles and hollow microspheres can be synthesized at pH 1 and 2, whereas individual Sb4O5Cl2 micro-belts become to form when the pH is higher than 3. The irregular-cuboids assembled Sb4O5Cl2 micro-particles and hollow microspheres exhibit self-narrowed bandgap and higher light absorption ability compared with individual Sb4O5Cl2 micro-belts. The photoelectrochemical measurements show that the assembled Sb4O5Cl2 hollow microsphere crystallites prepared at pH 2 exhibit enhanced carrier density, improved separation efficiency of electron-hole pairs and decreased electron-transfer resistance. As a result, the irregular-cuboids assembled Sb4O5Cl2 hollow microspheres prepared at pH = 2 exhibit the highest photocatalytic activity for the degradation of gaseous iso-propanol (IPA) and Rhodamine B (RhB) aqueous solution. The good photocatalytic activity of Sb4O5Cl2 sample prepared at pH = 2 may be caused by the synergistic effect of its higher light absorption, the decreased electron-transfer resistance, the suppressed recombination of photogenerated electrons and holes, and the increased surface area.

Ti-O-O coordination bond caused visible light photocatalytic property of layered titanium oxide.

The layered titanium oxide is a useful and unique precursor for the facile and rapid preparation of the peroxide layered titanium oxide H1.07Ti1.73O4·nH2O (HTO) crystal with enhanced visible light photoactivity. The H2O2 molecules as peroxide chemicals rapidly enter into the interlayers of HTO crystal, and coordinate with Ti within TiO6 octahedron to form a mass of Ti-O-O coordination bond in the interlayers. The introduction of these Ti-O-O coordination bonds result in lowering the band gap of HTO, and promoting the separation efficiency of the photo induced electron-hole pairs. Meanwhile, the photocatalytic investigation indicates that such peroxide HTO crystal has the enhanced photocatalytic performance for RhB degradation and water splitting to generate oxygen under visible light irradiating.

Ferroelectric mesocrystals of bismuth sodium titanate: formation mechanism, nanostructure, and application to piezoelectric materials.

Ferroelectric mesocrystals of Bi0.5Na0.5TiO3 (BNT) with [100]-crystal-axis orientation were successfully prepared using a topotactic structural transformation process from a layered titanate H1.07Ti1.73O4·nH2O (HTO). The formation reactions of BNT mesocrystals in HTO-Bi2O3-Na2CO3 and HTO-TiO2-Bi2O3-Na2CO3 reaction systems and their nanostructures were studied by XRD, FE-SEM, TEM, SAED, and EDS, and the reaction mechanisms were given. The BNT mesocrystals are formed by a topotactic structural transformation mechanism in the HTO-Bi2O3-Na2CO3 reaction system and by a combination mechanism of the topotactic structural transformation and epitaxial crystal growth in the HTO-TiO2-Bi2O3-Na2CO3 reaction system, respectively. The BNT mesocrystals prepared by these methods are constructed from [100]-oriented BNT nanocrystals. Furthermore, these reaction systems were successfully applied to the fabrication of [100]-oriented BNT ferroelectric ceramic materials. A BNT ceramic material with a high degree of orientation, high relative density, and small grain size was achieved.

Transformation of potassium Lindquist hexaniobate to various potassium niobates: solvothermal synthesis and structural evolution mechanism.

This paper introduces the formation reactions and reaction mechanisms of a series of potassium niobates from a potassium salt of the Lindquist hexaniobate [Nb6O19](8-) ion under solvothermal conditions. The structure and particle morphology of the potassium niobate product can be controlled easily with the reaction solution alkalinity using this solvothermal process. KNb3O8 with a plate-like morphology, K4Nb6O17·4.5H2O with a plate-like morphology, a new phase of K2Nb2O6·H2O with fibrous morphology, KNbO3 perovskites with cubic morphology are obtained at pH = 5.5, and in 0.3, 0.5, 1.0 mol L(-1) KOH solutions at 230 °C, respectively. The reaction conditions are much milder than those in the normal hydrothermal process. Furthermore, the K2Nb2O6·H2O fibers can be topotactically transformed into KNbO3 fibers, Nb2O5 fibers after H(+)-exchange-treatment, and LiNbO3 fibers after Li(+)-exchange-treatment by heat-treatments at 730, 560, and 520 °C, respectively. The formation reaction and structure of these potassium niobates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy-dispersive spectroscopy (EDS), Raman spectra and TG-DTA. The formation mechanism of this series of potassium niobates from the [Nb6O19](8-) precursor is systematically explained via the correlation between the octahedrons [NbO6] sharing forms in the precursor structure and in the product structures.