[en] ZnO-branched nanostructures have recently attracted considerable attention due to their rich architectures and promising applications in the field of optoelectronics. Contrary to n-type semiconducting metal oxides, cupric oxide is a p-type semiconductor which can be applied to high-critical-temperature superconductors, photovoltaic materials, field emission, and catalysis. We report the synthesis of the ZnO nanorods on the CuO nanofibers prepared by using the electrospinning method along with the hydrothermal method. As the growing time increases, emission spectra of the hetero-structured ZnO/CuO show that the observed band in the UV region is slightly increased, while the intensity of the green emission is highly enhanced. The hetero-structured ZnO/CuO is found to be a promising candidate for developing renewable devices with photoluminescent behavior and the increased surface to volume ratio.

[en] We have prepared ZnO nanofibers by using the electrospinning method and have analyzed the variations in their structure, optical properties, and chemical bonding states with the annealing temperature and the annealing conditions. After annealing at 500 .deg. C, the average diameter and the average grain size are determined to be approximately 170 nm and 50 nm, respectively. The ZnO nanofibers have a clearly visible dislocation-free crystal structure. The 2p level of Zn caused Zn-O bonds and the O 1s core level caused physisorbed O₂. When the nanofibers are annealed at 700 deg C, both ions exhibit shifts of the binding energies compared with those annealed at 500 .deg. C. The observed band in the visible region shows a strong temperature dependence and a red-shift with the oxygen flow in annealing process, which is related to oxygen vacancies.

[en] Magnesium ferrite (MgFe2O4) exhibiting a spinel phase was synthesized by using the polymerized complex and the solid-state reaction methods, and its physico-chemical properties were studied to explore the water-splitting under visible light photons. The study revealed the potential for using MgFe2O4 particles for photo-catalytic application. The structural study provided information on ferrite nano-crystallites fabricated by using the polymer complex method. The morphological studies demonstrated that, in contrast to the solid-state reaction method, a homogenous, monodispersed ferrite photocatalyst could be formed by using the polymerized complex method. The optical study revealed a larger visible-light absorption capability for the nanosized MgFe2O4 photocatalysts prepared by using the polymer complex methods, and indicated a red-shift of the bandgap by 0.06 eV as compared to the bandgap of the bulk. These nanocrystallites were highly photoactive with respect to the photodegradation and photocatalytic hydrogen evolution applications. The electrochemical analysis showed that they exhibited favorable bandedge positions suitable for photocatalytic H2 evolution. Thus, nanocrystalline MgFe2O4 is an active visible-light photocatalyst, that might be useful for the decomposition of water.

[en] Nanocrystalline ZnFe₂O₄ oxide-semiconductor with spinel structure was synthesized by the polymerized complex (PC) method and investigated for its photocatalytic and photoelectric properties. The observation of a highly pure phase and a lower crystallization temperature in ZnFe₂O₄ made by PC method is in total contrast to that was observed in ZnFe₂O₄ prepared by the conventional solid-state reaction (SSR) method. The band gap of the nanocrystalline ZnFe₂O₄ determined by UV-DRS was 1.90 eV (653 nm). The photocatalytic activity of ZnFe₂O₄ prepared by PC method as investigated by the photo-decomposition of isopropyl alcohol (IPA) under visible light (≥ 420 nm) was much higher than that of the ZnFe₂O₄ prepared by SSR as well as TiO_2-xN_x. High photocatalytic activity of ZnFe₂O₄ prepared by PC method was mainly due to its surface area, crystallinity and the dispersity of platinum metal over ZnFe₂O₄

[en] Zn₂Ti_1-xFe_xO₄ (0 ≤ x ≤ 0.7) photocatalysts were synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. Zn₂Ti_1-xFe_xO₄ can absorb not only UV light but also visible light region due to doping of Fe in the Ti site of Zn₂TiO₄ lattice because of the band transition from Fe 3d to the Fe 3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped Zn₂TiO₄ samples for hydrogen production under UV light irradiation decreased with an increase in Fe concentration in Zn₂TiO₄. Consequently, there exists an optimized concentration of iron for improved photocatalytic activity under visible light (λ ≥ 420 nm)

[en] Highlights: • Si-island with a micro-sized diameter is studied with respect to stress tolerance. • The space among neighboring Si-islands was able to suppress the strain during cycling. • After 100 cycles, 86.3% of the discharge capacity was retained for the Si-island electrode. - Abstract: A multi-layered graphene oxide-carbon/Si-island thin film/graphene oxide-carbon electrode is prepared as a very promising anode material for rechargeable Li-ion batteries. In this approach, graphene oxide-carbon layers are introduced to improve the adhesion (between the Si-island and copper current collector) and conductivity. The Si-island (diameter: 700 μm; array distance: 480 μm) is sputtered using a metal shadow mask. The strain during the insertion and extraction of the Li ions is adequately suppressed by the space among the neighboring Si-islands. This results in a superior cycle retention of 86.3% with a reversible discharge capacity of 940 mAh g⁻¹ after 105 cycles.

[en] The WO₃/W/PbBi₂Nb_1.9Ti_0.1O₉ photocatalyst was fabricated by depositing the tungsten clusters over the p-type perovskite base material with the chemical vapor deposition method, and later partly oxidizing the surfaces of these clusters to obtain n-type WO₃ overlayers and W metal layer as an Ohmic junction. This NCPC showed unprecedented high activity for the photocatalytic oxidation of water, photocurrent generation, and acetaldehyde decomposition under visible light irradiation (λ≥420 nm)

[en] Highlights: • EDTA was introduced into PAA to suppress the HF creation. • PAA/EDTA binder derived an exceptional cycling performance. • Si-PAA/EDTA electrode showed good thermal stability after temperature storage. The crucial roles of ethylenediaminetetraacetic acid (EDTA) in the poly(acrylic acid) (PAA)-binder system were investigated for the high electrochemical performance silicon anode in lithium-ion batteries. The EDTA supports the construction of a mechanically robust network through the formation of sbndCOOH linkage with the SiO₂ layer of the Si nanoparticles. The mixture of the PAA/EDTA binder and the conductive agent exhibited an improved elastic modulus and peeling strength. The creation of hydrogen fluoride (HF) was effectively suppressed through the elimination of the H₂O. An H₂O–phosphorous pentafluoride (PF₅) reaction, which is known for its use in the etching of metal oxides including its creation of the solid electrolyte interphase (SEI) layer, generates the HF. A remarkably sound cyclability with a discharge capacity of 2540 mA h g⁻¹ was achieved as a result of the synergistic effect between robust mechanical properties and suppression of the HF creation for the stability of the SEI layer.

[en] Pure and metal (Cu, Al, Sn, and V)-doped Li₄Ti₅O₁₂ powders are prepared with solid-state reaction method. The effects of dopants on the physical and electrochemical properties are characterized by using TGA, XRD, and SEM. Compared with pure Li₄Ti₅O₁₂, metal-doped Li₄Ti₅O₁₂ powders show structural stability and enhanced lithium ion diffusivity brought by doped metal ions. Voltage characteristics and initial charge–discharge characteristics according to the C rates in pure and metal-doped Li₄Ti₅O₁₂ electrode materials are studied. Pure Li₄Ti₅O₁₂ powder shows a relatively good discharge capacity of 164 mAh/g at a rate 0.2C, and some of metal-doped Li₄Ti₅O₁₂ powders show higher discharge capacities. Metal-doped Li₄Ti₅O₁₂ powders are promising candidates as anode materials for lithium-ion batteries.

[en] We synthesized an electrospun SnO_2 hollow nanofibers (SnO_2 hNFs) coated with carbon and wrapped with graphene oxide layer by simple hydrothermal and electrostatic force method, respectively. Thin carbon layer as electrolyte blocking layer was formed on the SnO_2 hNFs by using glucose as a carbon source (SnO_2@C hNFs). Also, layers of graphene oxide are wrapped on SnO_2@C hNFs by the electrostatic interaction force (SnO_2@C@G hNFs). At high C rate, the average capacity of the SnO_2@C@G hNFs still kept high capacity comparing with the SnO_2 hNFs and SnO_2@C hNFs and then increased above 250% at 3 C. It also exhibits a greatly enhanced synergic effect with an extremely high lithium storage capability up to 1,600 mA h g"−"1 and kept 900 mA h g"−"1 after 50 cycles benefiting from the advanced structural features