Xinxin Fu

Black Hydroxylated Titanium Dioxide Prepared via Ultrasonication with Enhanced Photocatalytic Activity.

The amorphous TiO2 derived from hydroxylation has become an effective approach for the enhancement of photocatalytic activity of TiO2 since a kind of special black TiO2 was prepared by engineering disordered layers on TiO2 nanocrystals via hydrogenation. In this contribution, we prepared totally amorphous TiO2 with various degrees of blackness by introducing hydroxyls via ultrasonic irradiation, through which can we remarkably enhance the photocatalytic activity of TiO2 with improved light harvesting and narrowed band gap.

Facile synthesis of graphene-supported mesoporous Mn3O4 nanosheets with a high-performance in Li-ion batteries

We report a room-temperature, facile and scalable strategy for the synthesis of Mn3O4 nanosheet/graphene nanocomposites. An important characteristic of these Mn3O4 nanosheets is their mesoporous nature and they have mesopores which are ∼4 nm in size. Such nanocomposites exhibit a high performance in lithium-ion batteries by virtue of this advantageous structural feature.

Synthesis of different CuO nanostructures from Cu(OH)2 nanorods through changing drying medium for lithium-ion battery anodes

Different CuO nanostructures have been successfully synthesized through changing the drying medium of Cu(OH)2 nanorods precursors. Herein, Cu(OH)2 nanorods precursors were first prepared through a simple precipitation method. When H2O was chosen as the drying medium at 80 °C, 2D leaf-like CuO nanostructures were obtained. While dried in ethanol 1D Cu(OH)2 nanorods were obtained. With post-annealing, porous CuO nanoleaves and nanocrystalline-assembled CuO nanorods were successfully synthesized, respectively, which have been applied to lithium batteries as anode materials and influence of different nanostructures on the electrochemical properties have been investigated. Fortunately, both novel nanostructured CuO successfully displayed high capacity and excellent cycling stability, and porous CuO nanoleaves can exhibit a reversible capacity of 633 mA h g−1 and 576 mA h g−1 after 100 and 150 discharge–charge cycles at 67.4 mA g−1, which is superior to that of CuO nanoleaves without post-annealing. These results may provide valuable insights for the industrialization and development of new nanostructured anodes for next-generation high-performance lithium-ion batteries.

Coordination-driven self-assembly: construction of a Fe3O4–graphene hybrid 3D framework and its long cycle lifetime for lithium-ion batteries

In this study, we have demonstrated coordination-driven self-assembly between Fe3O4 and graphene sheets under a hydrothermal condition for the simple in situ synthesis of a 3D Fe3O4–graphene hybrid architecture (Fe3O4/G). Fine hierarchical Fe3O4 spheres were homogeneously dispersed and embedded in an interconnected mesoporous framework of graphene sheets. It can be noted that the critical concentration of GO assembly decreased dramatically during the self-assembly of Fe3O4, indicating the coordination-driven self-assembly between Fe3O4 and GO. When evaluated as an anode material for LIBs, the Fe3O4/G hybrid framework demonstrates a high reversible capacity of 1164 mA h g−1 over 500 cycles at a current density of 500 mA g−1 and a remarkable rate capability. The superior electrochemical performance is attributed to a strong adhesion force and synergistic effect between Fe3O4 and graphene sheets as well as formation of a 3D interconnected hybrid framework, which offers enhanced kinetics towards electrochemical reactions with lithium ions and provides space for alleviating the huge volume expansion that occurs during charge–discharge cycles.

Carbonate-assisted hydrothermal synthesis of porous, hierarchical CuO microspheres and CuO/GO for high-performance lithium-ion battery anodes

Porous, hierarchical CuO microspheres (MSs) have been successfully synthesized through a facile, surfactant-free carbonate-assisted hydrothermal method. A growth mechanism based on self-aggregation and decomposition of precursor Cu2(OH)2CO3 nanoparticles and Ostwald ripening under hydrothermal conditions is proposed to explain the formation of CuO MSs. Then the CuO MSs are encapsulated with GO through engineering the ionic strength in solution and applied as anode materials for lithium ion batteries, which demonstrates that CuO/GO exhibits significant improvements over the bare CuO MSs. It can deliver a high reversible capacity of 500 mA h g−1 after 500 cycles, with 80% capacity retention of the second reversible capacity (625.8 mA h g−1) at a current density of 0.5C. This is much higher than 233.5 mA h g−1 of the bare CuO MSs at the same rate. Such significantly enhanced electrochemical performance of the CuO/GO hybrid can be attributed to the synergistic effect of successful integration of the CuO MSs with the highly conductive and flexible GO sheets. This study demonstrates that facile structural tuning of the metal oxide in combination with advantageous carbon materials is a promising way to fabricate anodes for high-performance lithium-ion batteries.

Enhanced photocatalytic activity of hydroxylated and N-doped anatase derived from amorphous hydrate

The hydrogenation on unmodified TiO2 to create disordered layers on the surface of anatase nanocrystals (NCs) in order to enhance the photocatalytic activity of TiO2 has been widely investigated in recent years. In this contribution, we prepared hydroxylated and N-doped anatase by controlling the degree of disorder of TiO2 derived from amorphous hydrate through a traditional pathway of heat treatment, which induced various colours in appearance and outstanding photocatalytic activities. The traditional method by heating to prepare hydroxylated TiO2 in this work is a reverse route compared to the pathway by hydrogenation, which opens opportunites for the modification of nano-dimension semiconductors derived from amorphous hydrates.

Bowl-like sulfur particles wrapped by graphene oxide as cathode material of lithium–sulfur batteries

We successfully synthesized sulfur particles with a bowl-like structure and wrapped them in graphene oxide (GO) via a simple method. The GO-wrapped bowl-like sulfur composite (GO-BS) with void space inside was used as cathode material of Li–S batteries, which realized the protection of active material and tolerance of volumetric expansion.

Self-assembled hierarchical mesoporous TiO2–C sub-microspheres from nanorods and their improved properties for lithium storage

Hierarchical TiO2 sub-microspheres (SMSs) constructed from anatase TiO2 nanorods (NRs) are prepared by a simple bottom-up self-assembly approach. The assembly process is achieved by dissolving the oleic acid-coated NRs into cyclohexane solution and refluxing at 80 °C without any other surfactants or complex steps. The TiO2–C nanocomposite is synthesized by carbonization and the amorphous carbon layer is formed in situ on the surface of the nanorods, which could improve the conductivity of the electrode. The hierarchical structures of TiO2–C SMSs are verified by BET test results, which shows a typical type-IV isotherm curve and the pore volume of the SMSs is approximately three times that of the NRs, indicating the formation of three-dimensional mesoporous networks. As a Li-ion battery anode material, the assembled TiO2–C SMSs exhibit better electrochemical performance with enhanced capacity, greater cyclic stability and better rate performance compared to those of unassembled NRs or P25. Moreover, any other oleic acid-coated nanocrystals could be prepared by adopting this bottom-up strategy.

Controllable synthesis of spherical anatase mesocrystals for lithium ion batteries

Spherical anatase mesocrystals have been successfully prepared in an acetic acid–tetrabutyl titanate–benzoic acid system via a facile solvothermal method. Based on the results of time-dependent experiments, a growth process is proposed for the spherical mesocrystals, which includes the formation of flower-like intermediates, the hydrolysis of these intermediates, and the precipitation and self-assembly of TiO2 nanocrystals. Benzoic acid plays an important role in the formation of the spherical morphology. Well-defined spherical anatase mesocrystals can be obtained only when the benzoic acid content is >4.5 g. As a result of their unique architecture (high crystallinity and a large specific surface area), the Li ion storage capabilities of these spherical mesocrystals were also investigated. The first discharge capacity is 314.5 mA h g−1 and the corresponding charge capacity is 224.3 mA h g−1, leading to a Coulombic efficiency of 71.3% at 0.2 C. Even under high current densities, such as 2 and 5 C, this anode material retains a good cycling stability and very high specific capacity.

Designed fabrication of anatase mesocrystals constructed from crystallographically oriented nanocrystals for improved photocatalytic activity

In this article, we report a new route to synthesize octahedral anatase mesocrystals (MCs), polycrystals (PCs) and single crystals (SCs) in the TiCl4–CH3COOH system just by tuning the reaction time and Ti-source concentration. Owing to the unique structures constructed from crystallographically oriented nanocrystals, MCs offer larger specific surface area than SCs and more effective electron transport compared with PCs. As anticipated, MCs show the highest photocatalytic activity in the degradation of methylene blue. MCs also demonstrate excellent cycle stability and renewable capability, and the photocatalytic efficiency still remains up to 90% even after five cycles. The designed fabrication of mesocrystals provides an attractive and effective route for improving the performances of semiconductor photocatalysts.