The charge/discharge process and electronic structure of iron hydroxyl-phosphate (Fe2−y◻y(PO4)(OH)3−3y(H2O)3y-2) are investigated by density functional theory (DFT) calculation under the GGA+U scheme. The calculation results show that the intermediate phase LixFe1.25(PO4)(OH)0.75(H2O)0.25 does not separate into the two end phases, Fe1.25(PO4)(OH)0.75(H2O)0.25 and Li1.25Fe1.25(PO4)(OH)0.75(H2O)0.25, during lithium insertion/extraction. The most striking feature of voltage−composition curve is the presence of a sloping voltage curve on charge and discharge, which is a characteristic of a single-phase charge/discharge behavior. It is attributed to the high concentration vacancy defects and the different topological and chemical local structures around the defects. No obvious band gap is observed, and unoccupied states locate around the Fermi level for the LixFe1.25(PO4)(OH)0.75(H2O)0.25 (0 < x<1). The energy band structure implies that this material is a two-dimensional electron conductor.

Cubic MnO with particle sizes of ∼200 nm and ∼600 nm was synthesized by decomposition of MnCO3. The corresponding MnO/C composite was obtained by thermal treatment of mixture of MnCO3 and sucrose. The structure and morphology of the products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical experiments showed that the as-prepared MnO/C exhibited promising electrochemical properties, and could potentially be used as anode material in lithium-ion batteries. MnO/C delivered a reversible capacity of about 470 mAh/g after cycling 50 times, when testing at 75 mA/g. The reversible capacity, when tested at 150, 375, 755 mA/g, reached 440, 320, 235 mAh/g, respectively. The good electrochemical performance was ascribed to the smaller particle size and the efficient carbon coating on MnO.Highlights► The synthesis of cubic MnO/C was more facile compared with those reported attempts. ► The as-prepared MnO/C shows good electrochemical properties. ► The reason for improvement of electrochemical performance was studied.

A composite Au@Bi2Cu0.1V0.9O5.35 (BICUVOX10) cathode is prepared and tested as a ceramal electrode for use in low-temperature solid-oxide fuel cells (SOFCs). Au powder is coated onto the surface of BICUVOX10 from an aqueous solution of the chloride with NaBH4 as a reductant. The valence of the surface Au is identified as Au(0) by X-ray photoelectron spectroscopy (XPS). The BICUVOX10 substrate is synthesized from V2O3, CuO, and Bi2O3 and then investigated by field-emission scanning electron microscopy (SEM). The average size of the particles is estimated to be 100 nm after milling with a planetary ball-mill. The core–shell structure of Au@BICUVOX10 is confirmed by transmission electron microscopy (TEM). The two-dimensional coefficient of thermal expansion (CTE) and the conductivities of mixed powders with different proportions of Au is also tested from room temperature to 600 °C. A single fuel cell is fabricated with Au@BICUVOX10 as the cathode, NiO/GDC (Gd0.1Ce0.9O1.95) as the supporting anode, and GDC as the electrolyte. The electrochemical performance is tested and the highest power densities of the fuel cell are determined to be 127, 206, 359, 469, and 474 mW cm−2 at 450, 500, 525, 550, and 575 °C, respectively. Finally, the stability of the single SOFC is tested, whereupon it is found that its output is maintained for at least the first 20 h.

Iron hydroxyl-phosphate with a uniform spherical particle size of around 1 μm, a compound of the type Fe2−y□y(PO4)(OH)3−3y(H2O)3y−2 (where □ represents a vacancy), has been synthesized by hydrothermal methods. The particles are composed of spheres of diameter <100 nm. The compound exhibits good electrochemical performance, with reversible capacities of around 150 mAh g−1 and 120 mAh g−1 at current densities of 170 mA g−1 and 680 mA g−1, respectively. The stability of crystal structure of this material was studied by TGA and XRD which show that the material remains stable at least up to the temperature 200 °C. Investigation of the electronic structure of the iron hydroxyl-phosphate by GGA + U calculation has indicated that it has a better electronic conductivity than LiFePO4.

A λ-MnO2 supported Pt nanocatalyst (5 wt.% Pt/λ-MnO2) was synthesized using a facile approach. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electronic microscope (SEM), transmission electron microscopy (TEM), and energy disperse spectroscopy (EDS) were used for catalyst structure and morphology characterization, which showed that the metallic Pt particles were attached on a λ-MnO2 surface through the interaction between Pt and λ-MnO2. Cyclic voltammetry (CV) was used to test the catalytic activity of Pt/λ-MnO2 toward methanol oxidation, which showed that Pt/λ-MnO2 catalyst has much higher catalytic activity than baseline Pt/C catalyst.

BiVO4 was synthesized from a mixture of aqueous Bi(NO3)3 and NH4VO3 solutions over a wide range of temperature via an easy hydrothermal method. The BiVO4 samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV–vis and Raman spectroscopy. Spherical and decahedral BiVO4 with better crystallinity can be obtained by changing the reaction temperature and adding the surfactant sodium dodecyl sulfate (SDS) to the mixed solutions. In addition, we have tested the photocatalytic activity of BiVO4 with the different morphologies. The highest initial rate of O2 evolution was 355 μmol h−1 under visible light radiation. This result indicates that BiVO4 prepared in our experiment is a promising photocatalyst in the visible light region.

Spinel Fe2VO4 was synthesized by solid state method and its properties were characterized using XRD, SEM, TG-DSC and specific surface area measurements. The average size of the particles was 500 nm. TG-DSC test demonstrated that the Fe2VO4 was thermally stable in nitrogen atmosphere within 300 °C. Lithium insertion into the sample at room temperature and 55 °C has been investigated and the highest discharge capacity approached 250 mAh/g at an average voltage of 0.6 V vs Li+/Li. Capacity retention was unexpectedly good at 1C discharge rate at room temperature and 55 °C. At 5C discharge rate, the specific capacity was still 136 mAh/g. The results show that the Fe2VO4 is a promising anode material due to its high specific capacity, thermal stability and rate performances.

AgCl and AgBr are a special type of superionic conductor, whose superionic phase transition does not accompany any first-order structural phase transition. In the paper, the ionic conductivity of AgBr is investigated by the first principles calculations with VASP code. The calculated results show that the isolated charged interstitial or vacancy is always more stable than the neutral one whether the system is doped or not; the interstitial hops along <001> direction, and the potential barrier is 0.29 eV; the vacancy hop mainly along <111> direction, and the barrier is 0.16 eV; the migration barrier of vacancy is obviously lower than that of interstitial, and then the ionic conductivity is mainly due to the diffusions of vacancies.

Au-Pt/SnO2/GC composite electrode was prepared by self-assembling Au-Pt nanoparticles on SnO2 film, which was deposited on actived glassy carbon (GC). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images revealed that dense and uniform Au-Pt particles with 25-nm diameter were dispersed on SnO2 film. X-ray photoelectron spectroscopy (XPS) results proved that there was an interaction between Au-Pt nanoparticles and SnO2 support. Electrochemical experiments showed that Au-Pt/SnO2/GC composite electrode had a good electrocatalytic activity to the oxidation of methanol.

LiCoPO4 micron-rods with an average diameter of about 500 nm and length of about 5 μm were synthesized by dispersant-aided hydrothermal method. Poly(n-vinylpyrrolidone) (PVP) was used as dispersant in the hydrothermal method. The starting solution and the concentration of dispersant have significant influences on the morphology of LiCoPO4, and the electrochemical performance is improved via controlling the particle size and morphology by the hydrothermal method. The cell using smaller particle LiCoPO4 as cathode delivers a larger capacity and lower cell polarization.

By using a facile one-pot synthetic route, we designed a one-dimensional hybrid nanostructure by introducing small amounts of Au species (0.9 wt %) dispersed over the amorphous tin oxide overlayers uniformly supported on coaxial carbon nanotubes as electrode materials for application in lithium ion battery. The as-synthesized CNT@SnO2−Au nanocables were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, elemental mapping, and X-ray photoelectron spectroscopy; such hybrid nanostructure markedly improves electrode performance, especially for the rate performance. The capacities of 467 and 392 mA h g−1 were obtained at rates of 3.6 A g−1 and 7.2 A g−1, respectively.

Spherical-like LiFePO4 was synthesized by hydrothermal synthesis method using Phenanthroline as a complexing-agent to avoid the Fe(II) ions from oxidation and control the growth of the crystal. Structural, electron valence state, morphology and particle size were investigated by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Mössbauer spectra, scanning electron microscopy (SEM) and laser particle sizer. Charge–discharge cycling performances were used to characterize its electrochemical properties. The sample possesses uniformly distributed spherical-like particles with an average size of 0.5–1 μm. Test shows that the reversible capacity of spherical-like LiFePO4 is about 140 mAh g−1 at 0.1 C. The capacity fading is neglectable.

Multi-walled carbon nanotubes (MWCNTs) coated with a smooth and uniform tin oxide (SnO2) layers of different thickness were prepared by a novel thioglycolic acid assisted one-step wet chemical method. The coatings were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thickness of the SnO2 coatings can be easily controlled by changing the synthesis conditions, such as pH value of the solution and hydrolysis time. The electrochemical properties of the SnO2/MWCNTs composites as anode materials for lithium batteries were studied by galvanostatic method. The composites showed high charge capacities and good durability against decay. This could be ascribed to the good dispersion, thin layer and small particle size of SnO2 on MWCNTs.

Titania of different crystalline structures and morphology was prepared by the low temperature dissolution–reprecipitation process (LTDRP) of amorphous precursors in various acidic mediums at 70 °C for 8 h. The effects of different acids on the crystalline and morphology of titania nanostructures were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results showed that HCl, HNO3 and their mixture favored the formation of rod-like rutile TiO2, while H2SO4 and its mixture with HCl or HNO3 retarded the formation of rutile but favored the formation of the anatase phase of with an irregular shape. The mechanism of the formation of various titania nanostructures was also discussed.

Multiwalled carbon nanotubes coated with SnO2 layers of different thickness were prepared by a simple wet-chemical method. The samples have been characterized by X-ray diffraction and transmission electron microscopy. The thickness of the coatings can be easily controlled by changing the synthesis conditions, such as pH value of the solution and hydrolysis time. The smoothness and uniformity of the SnO2 layers were greatly influenced by the addition of thioglycolic acid, which was used as connecter. The samples prepared by using thioglycolic acid showed very smooth and uniform coating layers, without cracks and broken segments. The growth behavior of the coating layer is also discussed.

The ionic conduction mechanisms of some super ionic conductors, α-AgI, β-Ag2S, and α-Ag2Se, have been investigated by means of ab-initio calculations using the VASP (Vienna Ab-initio Simulation Package) code. Each of these phases has a BCC (body-centered cubic) sub-lattice formed by the anions, while the cations, which partially occupy the 12d sites, migrate along pathways through the centers of the faces of the tetrahedra. The calculated band gaps of α-AgI, β-Ag2S, and α-Ag2Se are 0.88 eV, 0.06 eV, and 0 eV, respectively, which implies that α-AgI is only an ionic conductor, whereas β-Ag2S and α-Ag2Se are mixed electronic and ionic conductors.

Mo-doped LiFePO4 composite was synthesized by the solid state method, using (NH4)6Mo7O24·4H2O as the starting doping material. The electrochemical properties of Mo-doped LiFePO4 were measured. The electronic structures of Mo-doped LiFePO4 were studied by ab initio calculations. With respect to the density of states (DOS) of the LiFePO4, in which no electronic states are at the Fermi level, the Mo doping is predicted largely impacting the conductivity. Experimental data of the electronic conductivity and of the electrochemical performance of Mo-doped LiFePO4 synthesized by a solid state reaction confirm the results of the calculations. To characterize the doped LiFePO4 structure and the type and the symmetry of the Mo sites, X-ray absorption spectroscopy (XAS) experiments were performed.

Spherical bismuth vanadate particles are self-assembled from aqueous Bi(NO3)3 and NH4VO3 solutions by adjusting pH and tuning the amount of surfactant sodium dodecyl sulfate (SDS) via facile hydrothermal method. The BiVO4 samples were characterized by X-ray diffraction (XRD) and the peaks suited well with the pure phase monoclinic scheelite BiVO4. Field emission scanning electron microscopy (SEM) showed the average size of the spherical particles was 5 μm and the assembling stages in the hydrothermal synthesis process were recorded. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed the nanoparticles were single crystal. FT-IR spectroscopy test results demonstrated there was no SDS left in the samples. The mechanism of the self-assembling has also been proposed.