Junwei Sha

A large ultrathin anatase TiO2 nanosheet/reduced graphene oxide composite with enhanced lithium storage capability

A high-quality ultrathin anatase TiO2 nanosheet (ANT)/reduced graphene oxide (RGO) composite is successfully prepared by a simple one-step hydrothermal synthetic route. The unique 2-D integrative features and mesoporous characteristic of the ultrathin ATN/RGO composite with a large surface area and outstanding stability are very favorable for lithium storage. A high initial discharge capacity (256.4 mA h g−1 at 0.2C), a high initial Coulombic efficiency (86%), a high rate capability (225.7, 202, 183, 157, 118 and 88.3 mA h g−1 at 0.5, 1, 2, 5, 10, and 20C, respectively, 1C = 167.5 mA h g−1), and a superior cyclability (174.2 mA h g−1 after 200 cycles at 1C and 112.9 mA h g−1 after 260 cycles at 10C) are achieved by using the ultrathin ATN/RGO composite as an anode material for lithium-ion-batteries. A detailed comparative study of the electrochemical properties of P25 nanoparticles, ATNs, ATN/RGO, and ultrathin ATN/RGO composites reveals that the significantly enhanced lithium storage capability is attributed to the ultrathin TiO2 nanosheets with short ion diffusion paths facilitating Li+ insertion/extraction, RGO conductive supports for fast electron transport, and the extra Li storage at the RGO/TiO2 interface.

Graphene Oxide-Assisted Synthesis of Microsized Ultrathin Single-Crystalline Anatase TiO2 Nanosheets and Their Application in Dye-Sensitized Solar Cells

High-quality microsized ultrathin single-crystalline anatase TiO2 nanosheets (MS-TiO2) with exposed {001} facets were synthesized by a facile and low-cost two-step process that combines a graphene oxide (GO)-assisted hydrothermal method with calcination. Both GO and HF play an important role in the formation of well dispersed MS-TiO2. As a novel microsized (1-4 μm) ultrathin two-dimensional (2D) material, MS-TiO2 possesses much higher lateral size and aspect ratio compared to common 2D nanosized (30-60 nm) ultrathin TiO2 nanosheets (NS-TiO2), resulting in excellent electronic conductivity and superior electron transfer and diffusion properties. Here, we fabricated MS-TiO2 and NS-TiO2, both of which were incorporated with the TiO2 nanoparticles (P25) to constitute the hybrid photoanode of dye-sensitized solar cells (DSSCs), and explored the effect of the lateral size (nano- and micro-) of ultrathin TiO2 nanosheets on their electron transfer and diffusion properties. Benefiting from the faster electron transfer rate and short diffusion path of the MS-TiO2, the MS-TiO2/P25 gains the more superior performance compared to pure P25 and NS-TiO2/P25 in the application of DSSCs. Moreover, it is expected that the novel high aspect ratio MS-TiO2 may be applied in diverse fields including photocatalysis, photodetectors, lithium-ion batteries and others concerning the environment and energy.

A three-dimensional sponge of graphene nanoribbons crosslinked by Fe3O4 nanoparticles for Li+ storage

A three-dimensional sponge of graphene nanoribbons crosslinked by Fe3O4 nanoparticles (NPs), which is denoted as 3D Fe3O4@GNRs, is synthesized using a simple reflux procedure. In this hybrid, GNRs with open and active edges are used as building blocks while Fe3O4 NPs are employed not only as anode materials but as a crosslinking agent to weld GNRs at the joints, resulting in the assembly of a 3D porous sponge. The 3D Fe3O4@GNR hybrid exhibits super-high cycling performance (1700 mA h g−1 over 100 cycles at 0.1 A g−1) and excellent rate capability (1265 mA h g−1 at 1 A g−1), demonstrating a significant advancement in anode active materials with high energy density for lithium ion batteries.

Synthesis of novel carbon nano-chains and their application as supercapacitors

A chain-like carbon nanostructure, which we call as carbon nano-chains (CNCs), was synthesized through chemical vapor deposition (CVD). The influence of growth conditions (such as growth temperature, time and gas ratio) during CVD process on the carbon structures and the growth mechanism of the CNCs were investigated. To explore the potential application as electrode materials of supercapacitors, the electrochemical performances of the CNCs and the CNCs activated with KOH have been tested. The results indicated that the original CNCs exhibit relatively high specific surface area, high purity and regular framework, and favor growth at a moderate temperature and mild gas ratio. After activation, the CNCs have much improved specific surface area and porous structure. The electrochemical performance investigations showed that the activated CNCs have a power density of 159.6 kW kg−1 and an energy density of 15.5 W h kg−1, as well as excellent cycle stability, which is very superior to the original CNCs. This simple and low-cost preparation process and the superb electrochemical performance suggest great potential applications of activated CNCs in supercapacitors.