nH2O Nanorods Research Articles

Synthesis and Electrochemical Performance of the Orthorhombic V2O5·nH2O Nanorods as Cathodes for Aqueous Zinc Batteries.

Aqueous zinc-ion batteries offer the greatest promise as an alternative technology for low-cost and high-safety energy storage. However, the development of high-performance cathode materials and their compatibility with aqueous electrolytes are major obstacles to their practical applications. Herein, we report the synthesis of orthorhombic V2O5·nH2O nanorods as cathodes for aqueous zinc batteries. As a result, the electrode delivers a reversible capacity as high as 320 mAh g−1 at 1.0 A g−1 and long-term cycling stability in a wide window of 0.2 to 1.8 V using a mild ZnSO4 aqueous electrolyte. The superior performance can be attributed to the improved stability of materials, inhibited electrolyte decomposition and facilitated charge transfer kinetics of such materials for aqueous zinc storage. Furthermore, a full cell using microsized Zn powder as an anode within capacity-balancing design exhibits high capacity and stable cycling performance, proving the feasibility of these materials for practical application.

Effect of Sr2+ doping on sintering behavior, microstructural development and electrical properties of LaPO4·nH2O nanorods prepared by dry mechanical milling

The effect of Sr2+ doping on the presence of second phases, sintering behavior, microstructural development, and electrical properties of LaPO4·nH2O nanorods (La1−xSrxPO4−x/2 where x = 0.025 and 0.05) obtained by a dry mechanochemical milling process was investigated. When Sr2+ is present monazite-type La1−xSrxPO4 nanopowders were obtained instead of rhabdophane-type LaPO4·nH2O. In addition, Sr2+ doping implies a larger P/La ratio and it enhances the formation of lanthanum tryoxophosphate (La(PO3)3), a thermodinamically stable phase, in doped samples. Dilatometric studies reveal a shift of the maximum shrinkage rate at lower temperatures for doped samples, with larger shifts with higher Sr2+ contents. This shift is related to the presence of oxygen vacancies but also to a higher content of La(PO3)3. Furthermore, the derivative of the linear shrinkage curves for all the samples showed peaks at temperatures higher than 1300 °C that are associated to the volatilization of P4O10 gas and to the recrystallization of monazite from the incongruent melting of La(PO3)3. After the dilatometric tests at 1500 °C the samples showed polygonal grains with a bimodal size distribution. For the doped samples the smaller grains do not present Sr2+ in their composition and it is related to those grains form from the recrystallization of monazite-LaPO4 formed in turn from La(PO3)3. The total conductivity of the studied samples (x = 0.05) is higher for the samples sintered at 1000 °C for 1 h than for those sintered at 1500 °C without any dwell time. It can be due in part to the fact that the smaller grains of the samples sintered at 1500 °C do not contain Sr2+ and it can hinder the charge transport.

Effect of Tb3+ doping and self-generated pressure on the crystallographic/morphological features and thermal stability of LaPO4·nH2O single-crystal nanorods obtained by microwave-assisted hydrothermal synthesis

The effect of Tb3+-doping content (in the range 0–20mol%) and autogeneous/self-generated pressure (in the range 2.3–3.4±0.1bar) on the crystallographic/morphological features and thermal stability of single-crystal nanorods of LaPO4·nH2O obtained by a simple and fast microwave-assisted hydrothermal synthesis was investigated. It is shown that high-quality (that is, well-shaped and linear/planar defect free) rhabdophane-type single-crystal La1-xTbxPO4·nH2O (x=0–0.20) nanorods, with a high morphological uniformity, are obtained in all cases. In addition, it is shown that the Tb3+ solutes are incorporated into the LaPO4·nH2O host, forming substitutional solid solutions (i.e., partial substitution of La3+ by Tb3+) with progressively smaller unit-cell volume but with identical thermal stability. Morphologically Tb3+ doping however results in the formation of nanorods with lower aspect ratio. With respect to the self-generated pressure during the microwave synthesis, it is shown that its increase does not affect to crystallographic aspects, but however results again in nanorods with lower aspect ratio. It is also demonstrated that monazite-type single-crystal La1-xTbxPO4 nanorods can be obtained by calcining their rhabdophane-type La1-xTbxPO4·nH2O counterparts at ~700°C in air. Consequently, in the present study important guidelines have been identified for the controlled synthesis of functional La1-xTbxPO4·nH2O nanorods with tailored morphology.

Thermal evolution, second phases, and sintering behavior of LaPO4·nH2O nanorods prepared by two different chemical synthesis routes

Thermal evolution and sintering behavior of LaPO4·nH2O, prepared by two different chemical synthesis routes, are presented in this work as a comparative study. The presence of polytrioxophosphate (La(PO3)3) in the as-synthesized powders, as minor second phase, and its consequences on thermal and sintering behavior are also discussed.At temperatures ~1000°C, the samples suffer a weight loss that could be caused by the volatilization of P4O10 during the incongruent melting of the polytrioxophosphate. Furthermore, the derivative curves of the linear shrinkage show peaks at temperatures higher than 1000°C that can be also related to that process. HREM–SAED–XEDS showed an amorphous phase in samples calcined at 800°C/12h that surrounds the boundaries of La(PO3)3 crystals and according to XEDS analyses corresponds to LaPO4. In addition, a glassy phase is also detected at some grain boundaries in sintered samples after polishing and thermal etching.

Hierarchical m‐ZrO2 Nanorods Template‐Free Synthesis by Hydrothermal Method

Hierarchical m‐ZrO2 nanorods synthesized by the simple hydrothermal method, and the possible formation mechanism was proposed based on a series of chemical reactions. The as‐synthesized products are composed of many 1D ZrO2·nH2O nanorods with 150–250 nm in diameter and 6–8 μm in length. The final product after annealing at the 700°C was involved into hierarchical monoclinic m‐ZrO2 nanorods, and the big nanorod was made up of many small nanorods with 10–20 nm in diameter and 400–500 nm in length. This discovery could helpful in understanding, the chemical properties of ZrB2 and ZrO2, the design of its derivatives for m‐ZrO2 nanomaterials.

Synthesis, characterization and electrochemical performance of graphene decorated with 1D NiMoO4·nH2O nanorods

One-dimensional NiMoO4 · nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4 · nH2O, a maximum specific capacitance of 161 F g(-1) was obtained at 5 A g(-1) current density, accompanied with an energy density of 4.53 W h kg(-1) at a steady power delivery rate of 1125 W kg(-1). The high utility of the pseudocapacitive NiMoO4 · nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g(-1) at 5 A g(-1) current density and a high energy density of 10.32 W h kg(-1) at a power density of 1125 W kg(-1) accompanied with long term cyclic stability.

Hydrothermal Synthesis of Neodymium Orthophosphate with Controlled Structure and Morphology

NdPO4•nH2O nanorods with a pure hexagonal and monoclinic phase were controlled synthesized through a hydrothermal route at low temperature. By simply increasing the molar ratio of PO4/Nd, pure monoclinic NdPO4can be obtained at lower temperature of 180 °C. Furthermore, NdPO4•nH2O nanorods can be assembled into flower- or bundle-shape. The reactant molar ratio played key roles in the formation of the products with different morphologies and structures. The possible formation mechanism for NdPO4 nanorods with different morphologies and structures was discussed. In addition, low-cost preparation of NdPO4 nanorods could be achieved through cycling use of phosphoric acid. Furthermore, this synthesis strategy will open a novel approach to rare earth phosphates with multiple structures.

High-Performance Li-ion Batteries and Supercapacitors Base on 1-D Nanomaterials in Prospect

One-dimensional (1-D) nanomaterials with superior specific capacity, higher rate capability, better cycling peroperties have demonstrated significant advantages for high-performance Li-ion batteries and supercapacitors. This review describes some recent developments on the rechargeable electrodes by using 1-D nanomaterials (such as LiMn2O4 nanowires, carbon nanofibers, NiMoO4 · nH2O nanorods, V2O5 nanoribbons, carbon nanotubes, etc.). New preparation methods and superior electrochemical properties of the 1-D nanomaterials including carbon nanotube (CNT), some oxides, transition metal compounds and polymers, and their composites are emphatically introduced. The VGCF/LiFePO4/C triaxial nanowire cathodes for Li-ion battery present a positive cycling performance without any degradation in almost theoretical capacity (160 mAh/g). The Si nanowire anodes for Li-ion battery show the highest known theoretical charge capacity (4277 mAh/g), that is about 11 times lager than that of the commercial graphite (∼372 mAh/g). The SWCNT/Ni foam electrodes for supercapacitor display small equivalent series resistance (ESR, 52 mΩ) and impressive high power density (20 kW/kg). The advantages and challenges associated with the application of these materials for energy conversion and storage devices are highlighted.

High-Performance Li-ion Batteries and Supercapacitors Based on Prospective 1-D Nanomaterials

Abstract One-dimensional (1-D) nanomaterials with superior specific capacity, higher rate capability, better cycling peroperties have demonstrated significant advantages for high-performance Li-ion batteries and supercapacitors. This review describes some recent developments on the rechargeable electrodes by using 1-D nanomaterials (such as LiMn2O4 nanowires, carbon nanofibers, NiMoO4 · nH2O nanorods, V2O5 nanoribbons, carbon nanotubes, etc.). New preparation methods and superior electrochemical properties of the 1-D nanomaterials including carbon nanotube (CNT), some oxides, transition metal compounds and polymers, and their composites are emphatically introduced. The VGCF/LiFePO4/C triaxial nanowire cathodes for Li-ion battery present a positive cycling performance without any degradation in almost theoretical capacity (160 mAh/g). The Si nanowire anodes for Li-ion battery show the highest known theoretical charge capacity (4277 mAh/g), that is about 11 times lager than that of the commercial graphite (∼372 mAh/g). The SWCNT/Ni foam electrodes for supercapacitor display small equivalent series resistance (ESR, 52 mΩ) and impressive high power density (20 kW/kg). The advantages and challenges associated with the application of these materials for energy conversion and storage devices are highlighted.

Synthesis and conductivity of GdPO 4 nanorods: Impacts of particle size and Ca 2+ doping

A series of Gd 1− x Ca x PO 4· nH 2O nanorods were prepared using a simple hydrothermal reaction which was optimized by tuning the pH values of the precursor. The resulted nanorods were characterized by X-ray diffraction, transmission electron microscopy, Fourier transformation infrared spectroscopy, and alternative current impedance technique. It is demonstrated that all Gd 1− x Ca x PO 4· nH 2O nanorods crystallized in a pure hexagonal structure. For x = 0, the particle dimension decreased with increasing the pH value. For x > 0, the solid solution limit of Ca 2+ in GdPO 4· nH 2O nanorods was about 3 mol%, below which the lattice volume increased with increasing the doping level of Ca 2+. The conductivities of nanorods were highly dependent on both the particle size and Ca 2+ concentration, as indicated by the increased conductivity as particle size reduces or Ca 2+ doping level increases. These observations were understood in terms of the dehydration and the introduction of HPO 4 2− defects by Ca 2+ doping.

Synthesis, Characterization, and Lithium Storage Capability of AMoO4 (A = Ni, Co) Nanorods

One-dimensional (1D) AMoO4·nH2O (A = Ni, Co) nanorods have been synthesized by a facile hydrothermal method. The effect of different synthetic conditions on the morphologies of the final products was systematically investigated. The size of the nanorods can be easily controlled by adding ethanol in the synthetic solution. For the first time, the self-assembled growth of oriented NiMoO4·nH2O nanorod arrays on Ti-foil substrates was achieved. The thermal dehydration and phase transformation processes of AMoO4·nH2O nanorods were thoroughly investigated by TG-DTA and time-resolved synchrotron XRD. As-prepared hydrate nanorods can be further converted to corresponding AMoO4 nanorods by annealing at 300−600 °C for 1 h without significant alteration of 1D morphology. Electrochemical lithium storage capabilities of dehydrated AMoO4 nanorods have been investigated. The results suggest their potential use as cathode materials for lithium ion batteries.

Facile, alternative synthesis of lanthanum phosphate nanocrystals by ultrasonication

Highly luminescent, rhabdophane (Ce 0.33La 0.66)PO 4⋅ nH 2O nanorods and nanoparticles were prepared in aqueous solutions by ultrasonication, at pH 1 and pH 12, respectively. Both nanorods (5 to 9 nm wide and several tens to several hundreds nm long) and nanoparticles (elongated, connected 5 nm particles) were as small and as uniform as products obtained from methods that utilize complexing agents or surfactants, only with no complexing agent. This method of synthesis by ultrasonication is a fast and simple method and it is expected to be applicable for the synthesis of other nanocrystalline lanthanide phosphates.

Dimensional Control of Cobalt-hydroxide-carbonate Nanorods and Their Thermal Conversion to One-Dimensional Arrays of Co3O4 Nanoparticles

We report a detailed investigation on the formation of cobalt-basic-carbonate compounds [Co(OH)x(CO3)0.5(2-x)·nH2O] with dimensional and morphological controls. Two complementary precipitation methods developed in this work produce cobalt-basic-carbonate in the form of nanorods across a wide diameter span from 2 to 200 nm and a length up to 5 μm. Various controlling parameters were examined, such as anions in starting reagents, reaction temperature, aging time, and chemical compositions between the solid products and starting reagents. The resultant solids were characterized using XRD, FTIR, CHN, and TGA/DrTGA methods with respect to their formation process and thermal decomposition. More importantly, morphological aspects of the Co(OH)x(CO3)0.5(2-x)·nH2O and their heat-treated product Co3O4 were investigated with TEM/ED methods. It has been found that the Co(OH)x(CO3)0.5(2-x)·nH2O nanorods are grown along the [010] direction (orthorhombic). Upon thermal decomposition at ≥300 °C, the above nanorods self-assemble into one-dimensional arrays of Co3O4 nanoparticles along the [111] axis (cubic) of the spinel. Co3O4 nanorods can be prepared with this method in a small diameter regime of 20−40 nm.

Starlike nanostructures of polyoxometalates K3[PMo12O40].nH2O synthesized and assembled by an inverse microemulsion method.

In a nonionic inverse microemulsion system, surfactant (C12-18EO9)/cyclohexane/water, heteropolyanions [PMo12O40]3- react with K+ to form K3[PMo12O40].nH2O nanorods and assemble as three-dimensional starlike nanostructures.