Jiantao Zai

Highly Efficient Ag2O/Bi2O2CO3 p-n Heterojunction Photocatalysts with Improved Visible-Light Responsive Activity

Ag2O/Bi2O2CO3 p-n heterojunctions are prepared with commercial Bi2O2CO3 as precursor via a simple photosynthesis process. The obtained Ag2O/Bi2O2CO3 p-n heterojunctions show higher photocatalytic activity than that of pure n-Bi2O2CO3, and the obtained Ag2O/Bi2O2CO3 (AB-4) heterojunction exhibits the best photocatalytic activity under visible light (λ > 400 nm), with which Rhodamine B, methyl blue and methyl orange can be completely degraded within 12 min. Photoluminescent spectra and photoelectrochemical measurement further indicate that the Ag2O/Bi2O2CO3 p-n heterojunctions greatly enhance the charge generation and suppress the charge recombination of photogenerated electron-hole pairs, which would be beneficial to improve their photocatalytic activity.

Hierarchical Bi2O2CO3 microspheres with improved visible-light-driven photocatalytic activity

A high-efficiency Bi2O2CO3 photocatalyst was successfully synthesized using tri-sodium citrate as both the coordinating agent and carbon source through a hydrothermal process. Morphology modulation of the obtained products could be easily realized by tuning the concentration of tri-sodium citrate in sponge-like, rose-like and plate-like shapes. The as-prepared sponge-like Bi2O2CO3 microspheres, owning a narrowed band gap of 2.87 eV and a higher BET surface area of 43.99 m2 g−1, exhibit powerful visible-light-photocatalytic activity for the degradation of dyes under 300 W Xe lamp light irradiation. It is worthy to note that the optimal sponge-like Bi2O2CO3 microspheres also possess superior photocatalytic ability under natural sunlight.

Novel Bi2S3/Bi2O2CO3 heterojunction photocatalysts with enhanced visible light responsive activity and wastewater treatment

Novel Bi2S3/Bi2O2CO3 heterojunction photocatalysts were prepared by a simple chemical reaction from commercial Bi2O2CO3. The photocatalytic activities of Bi2S3/Bi2O2CO3 were evaluated by degrading Rhodamine B (RhB) under visible light and sunlight irradiation. Further investigation revealed that the content of loading bismuth sulfide (Bi2S3) had important effects on the photocatalytic activity of the Bi2S3/Bi2O2CO3 heterojunctions, and the 5xa0mol% Bi2S3/Bi2O2CO3 heterojunction photocatalyst exhibited the best photocatalytic activity (30 min under visible light, λ > 400 nm). The high photocatalytic activity could be attributed to its good visible light absorption, facilitated charge separation of photogenerated electron–hole pairs and efficient charge transfer path in the partly exposed core in the heterojunctions. These benefits are derived from the unique band gap structure of the Bi2S3/Bi2O2CO3 n–n-type heterojunctions and special morphology with the partly exposed core, which was confirmed by photoluminescent spectra, surface photovoltage spectra and photoelectrochemical characterizations.

MnFe2O4–graphene nanocomposites with enhanced performances as anode materials for Li-ion batteries

MnFe(2)O(4)-graphene nanocomposites (MnFe(2)O(4)-GNSs) with enhanced electrochemical performances have been successfully prepared through an ultrasonic method, e.g., approximate 1017 mA h g(-1) and 767 mA h g(-1) reversible capacities are retained even after 90 cycles at a current density of 0.1 A g(-1) and 1 A g(-1), respectively. The remarkable improvement in the reversible capacity, cyclic stability and rate capability of the obtained MnFe(2)O(4)-GNSs nanocomposites can be attributed to the good electrical conductivity and special structure of the graphene nanosheets. On the other hand, MnFe(2)O(4) also plays an important role because it transforms into a nanosized hybrid of Fe(3)O(4)-MnO with a particle size of about 20 nm during discharge-charge process, and the in situ formed hybrid of Fe(3)O(4)-MnO can be combined with GNSs to form a spongy porous structure. Furthermore, the formed hybrid can also act as the matrix of MnO or Fe(3)O(4) to prevent the aggregation of Fe(3)O(4) or MnO, and accommodate the volume change of the active materials during the discharge-charge processes, which is also beneficial to improve the electrochemical performances of the MnFe(2)O(4)-GNSs nanocomposites.

3D-hierarchical SnS2 micro/nano-structures: controlled synthesis, formation mechanism and lithium ion storage performances

Three kinds of 3D-hierarchical SnS2 micro/nano-structures were successfully synthesized through a one-pot hydrothermal method by controlling the ratio of SnCl4 and L-cysteine. It was found that these obtained 3D-hierarchical SnS2 structures had great differences in their chemical composition, crystalline property, building blocks, assembling format and porous structure. The formation processes of the hierarchical structures were studied well and the possible mechanisms were also proposed. The lithium storage properties of these 3D-hierarchical SnS2 structures were carefully studied by charge-discharge test and cyclic voltammetry method. The results indicated that the crystalline properties of the electrode materials could influence the initial electrochemical reactivity and the small size of building blocks could greatly improve the reversibility of electrochemical reaction and rate performances. Furthermore, the large surface area, porous structure and free space derived from the 3D hierarchical structures were beneficial to the long-term cycling stability of electrode materials.

Self-assembled heavy lanthanide orthovanadate architecture with controlled dimensionality and morphology.

Nearly monodisperse YVO(4) architectures with persimmon-like, cube-like and nanoparticle shapes have been synthesised on a large scale by means of a complexing-agent-assisted solution route. The shape and size of these as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as reaction time, the molar ratio of complexing agent/Y(3+) and different complexing agents. As a typical morphology, the growth process of monodisperse nanopersimmons has been examined. To extend this method, other LnVO(4) (Ln=Ce, Gd, Dy, Er) complexes with well-defined shape and dimensionality can also be achieved by adjusting different rare earth precursors. Further studies reveal that the morphology of the as-synthesised lanthanide orthovanadate is determined mainly by the interaction between rare earth ion and the complexing agent. Ultraviolet (UV) absorption and photoluminescence spectra show that the optical properties of YVO(4) nanopersimmons are relevant to their size and shape. This work sheds some light on the design of well-defined complex nanostructures, and explores the potential applications of the as-synthesised architectures.

3D-hierarchical NiO–graphene nanosheet composites as anodes for lithium ion batteries with improved reversible capacity and cycle stability

3D-hierarchical NiO–graphene nanosheet (GNS) composites as high performance anode materials for lithium-ion batteries (LIBs) were synthesized through a simple ultrasonic method, and characterized by X-ray diffraction, Raman spectrum, field emission scanning electron microscopy and transmission electron microscopy. The results show that the 3D-hierarchical NiO carnations with nanoplates as building blocks are homogeneously anchored onto GNS and act as spacers to reduce the stacking of GNS. Electrochemical performances reveal that the obtained 3D-hierarchical NiO–GNS composites exhibit remarkably high reversible lithium storage capacity, good rate capability and improved cycling stability, e.g. approximate 1065 mA h g−1 of reversible capacity is retained even after 50 cycles at a current density of 200 mA g−1. The remarkable improvement of electrochemical performances of the obtained composites could be attributed to the decrease of the volume expansion and contraction of NiO and the improvement of the electronic conductivity of composites during the cycling process.

Nearly monodispersed In(OH)3 hierarchical nanospheres and nanocubes: tunable ligand-assisted synthesis and their conversion into hierarchical In2O3 for gas sensing

In(OH)3 nanomaterials with different morphologies or hierarchical structures, such as nanoparticles, monodispersed hierarchical nanocubes and nanospheres, have been successfully synthesized via a ligand-assisted aqueous process. The shape and size of these as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as the molar ratio of ligand/In3+ and different ligands. Further studies reveal that both Na3cit and urea are necessary for the formation of monodispersed hierarchical nanospheres and nanocubes. Furthermore, In2O3 nanoparticles and monodispersed hierarchical nanocubes and nanospheres with well-defined morphologies of the precursors can be also obtained by annealing the corresponding In(OH)3 samples. The gas sensing properties of the as-prepared In2O3 samples demonstrate that hierarchical In2O3 architectures exhibit a superior response to ethanol gas, and the hierarchical In2O3 nanocubes have excellent selectivity and sensitivity. Further more, XPS spectra and N2 adsorption–desorption isotherms achieve a deeper understanding of the effects of the final product morphologies on their gas sensing properties.

Ultrathin FeSe2 Nanosheets: Controlled Synthesis and Application as a Heterogeneous Catalyst in Dye‐Sensitized Solar Cells

Two-dimensional (2D) semiconducting nanosheets have emerged as an important field of materials, owing to their unique properties and potential applications in areas ranging from electronics to catalysis. However, the controlled synthesis of ultrathin 2D nanosheets remains a great challenge, due to the lack of an intrinsic driving force for anisotropic growth. High-quality ultrathin 2D FeSe2 nanosheets with average thickness below 7u2005nm have been synthesized on large scale by a facile solution method, and a formation mechanism has been proposed. Due to their favorable structural features, the as-synthesized ultrathin FeSe2 nanosheets exhibit excellent electrocatalytic activity for the reduction of triiodide to iodide and low charge-transfer resistance at the electrolyte-electrode interface in dye-sensitized solar cells (DSSCs). The DSSCs with FeSe2 nanosheets as counter electrode material achieve a high power conversion efficiency of 7.53% under a simulated solar illumination of 100u2005mWu2009cm(-2) (AMu20051.5), which is comparable with that of Pt-based devices (7.47%).

TiO2 coated urchin-like SnO2 microspheres for efficient dye-sensitized solar cells

AbstractUrchin-like SnO2 microspheres have been grown for use as photoanodes in dye-sensitized solar cells (DSSCs). We observed that a thin layer coating of TiO2 on urchin-like SnO2 microsphere photoanodes greatly enhanced dye loading capability and light scattering ability, and achieved comparable solar cell performance even at half the thickness of a typical nanocrystalline TiO2 photoanode. In addition, this photoanode only required attaching ∼55% of the amount of dye for efficient light harvesting compared to one based on nanocrystalline TiO2. Longer decay of transient photovoltage and higher charge recombination resistance evidenced from electrochemical impedance spectroscopy of the devices based on TiO2 coated urchin-like SnO2 revealed slower recombination rates of electrons as a result of the thin blocking layer of TiO2 coated on urchinlike SnO2. TiO2 coated urchin-like SnO2 showed the highest value (76.1 ms) of electron lifetime (τ) compared to 2.4 ms for bare urchin-like SnO2 and 14.9 ms for nanocrystalline TiO2. TiO2 coated SnO2 showed greatly enhanced open circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF) leading to a four-fold increase in efficiency increase compared to bare SnO2. Although TiO2 coated urchin-like SnO2 showed slightly lower cell efficiency than nanocrystalline TiO2, it only used a half thickness of photoanode and saved ∼45% of the amount of dye for efficient light harvesting compared to normal nanocrystalline TiO2.n