Kaifeng Yu

Preparation of disordered carbon from rice husks for lithium-ion batteries

Rice husk (RH) was employed as a precursor for the preparation of disordered carbon for lithium-ion batteries. Disordered carbon was synthesized by pyrolysis of RH under an inert gas atmosphere followed by base treatment to remove the silica fraction. These carbons were characterized through X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurements, scanning electron microscopy (SEM), Raman spectroscopy and transmission electron microscopy (TEM). The effects of reaction temperature for NaOH treatment on the capacity of these carbons were described. These carbons showed a high reversible capacity of 502 mA h g−1 after 100 cycles at 0.2 C in lithium-ion battery anodes.

Fabrication of TiO2 hollow nanocrystals through the nanoscale Kirkendall effect for lithium-ion batteries and photocatalysis

TiO2 hollow structures have important applications in high performance lithium ion batteries and efficient photocatalysis. In contrast to the conventional synthesis routes where various soft or hard templates are usually put into use, the direct growth of uniform TiO2 hollow nanocrystals is presented. The growth mechanism, lithium ion battery performance, and photocatalytic activity of the resultant TiO2 hollow nanocrystals are thoroughly investigated. TiO2 hollow nanocrystals can be synthesized through a mechanism analogous to the nanoscale Kirkendall effect. The hollow structure results in highly active photocatalysis, high rate capability, and stable cycling.

Preparation and Photocatalytic Property of Nickel-Doped Titanium Dioxide Nanotubes

The nickel-doped titanium dioxide nanotubes were prepared by Sol-gel and hydrothermal method and used to photodecompose methylene blue (MB) in liquid phase under visible light irradiation. The anatase-type titania nanotubes were shown to be hollow scrolls with outer diameter of about 10–15 nm and length of several hundred nanometers. The photocatalytic properties of Ni-doped titanium dioxide nanotubes and nanopowders were studied by degrading of MB. The results show that appropriate content of nickel can effectively enhance the photocatalytic activity of titanium dioxide nanotubes.

Graphene grown in situ on TiO2 hollow nanocrystals for advanced photocatalysis and lithium-ion batteries

Graphene nanosheets (GAs) grown on TiO2 hollow nanocrystals have been successfully fabricated for the first time via a simple one-step hydrothermal method for advanced photocatalysis and lithium ion batteries. The current study has shown that the nanocomposite materials can better decompose organic pollutants and can provide the additional electron transport pathways implying a significant potential for application in photocatalysis and LIBs. The nanocomposite materials have shown highly active photocatalysis, and high rate capability, and stable cycling. Furthermore, the nanocomposite materials with 1% graphene exhibit the best photoelectrical properties and Li-ion insertion/extraction kinetics in TiO2.

Preparation of highly mesoporous honeycomb-like TiO2 and its excellent application

TiO2 has poor photocatalytic performance when synthesised using traditional processes under visible light, which has limited its practical applications. In this work, titanium sulfate and hydrazine hydrate were used as raw materials to fabricate highly mesoporous honeycomb TiO2via a two-step hydrothermal and calcination method. The formation mechanism of the highly mesoporous TiO2 was analyzed based on experiments and theories. The parameters were flexible using the preparation method. Samples with high photocatalytic performance can be obtained without strictly controlling the process parameters such as hydrazine hydrate dosage, the hydrothermal temperature and so on. The preparation process was as follows: the raw materials were prepared at 180 °C for 48 h in the first hydrothermal stage, and then synthesized at 150 °C for 48 h in the second hydrothermal process. The hydrazine hydrate dosage was 10 ml in the second process. The prepared grain sizes were about 16.4 nm and the specific surface areas were approximately 105.12 m2 g−1 after the samples were heated at 450 °C for 4 h. Their degradation rate was 1.8 times that of P25. The improved performances are ascribed to the unique point defects because of nitrogen atom doping in the TiO2 and the highly mesoporous structure increased by adding hydrazine hydrate.

A New Way for Preparation and Characterization of Cr-Doped LiMnO2 Cathode Materials for Lithium Ion Batteries

o-LiMnO2 and LiMn1−xCrxO2 (x = 0.1) powders were synthesized via hydrothermal method after being calcined. Crystalline structure, surface morphology, and electrochemical properties of the prepared powders are investigated by XRD, SEM, and cyclic voltammetric studies. From the results, it was found that LiMnO2 cathode with a small amount of doping Cr is mostly orthorhombic forms. It could not only affect the structure of the specimens, but also improve cycling performance and reversible capacity and it could reach 190 mAh/g after 50 cycles.

TiO2 Nanoflakes as Anode Material for Lithium Ion Batteries

The mesoporous TiO2 nanoflakes have been prepared by the hydrothermal method, which is using Ti(SO4)2 as the titanium raw and KOH solution as alkaline medium. The TiO2 nanoflakes have been characterizated by transmission electron microscopy, X-ray powder diffraction, N2 adsorption–desorption analysis, cyclic voltammetry, and cycle performance test. Electrochemical performance test shows that mesoporous TiO2 nanoflakes have high discharge specific capacity and good cycle performance. Discharge specific capacity for the first time is in 0.2 C ratio of 278.1 mAh g−1. After 90 cycles, the discharge capacity reduces to 97.6% of the theoretical specific capacity.

Excellent photocatalytic performance of cobalt-doped titanium dioxide nanotubes under ultraviolet light:

To improve the photocatalytic property of titanium dioxide, titanous sulfate as the titanium source, cobalt nitrate hexahydrate as the cobalt source, undoped and Co2+-doped titania nanotubes were prepared via coprecipitation method combined with hydrothermal synthesis. Based on the degradation rate of methylene blue, the effects of the codoped rate on photocatalytic activities of the sample were researched. The result showed that doping cobalt could improve the photocatalytic performance of the titanium dioxide nanotubes under the ultraviolet light. The composition and structure of the samples were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. Conclusions indicated that the low-concentration Co2+ has no influence on the crystal structure of titanium dioxide and no new crystals were formed in the whole process.

Preparation and Characterization of Lepidocrocite Titanate Nanofibers

One-dimensional nanostructures have attracted much attention due to their potential application in a variety of novel devices[1-3].Among the one-dimensional oxide nanomaterials reported,titanium oxide is of particular interest for its wide application in the fields of catalyst support[4],semiconductor photocatalyst[5] and sensor[6].Since the first report claiming the hydrothermal synthesis of titania nanobubes[7],there have been intensive studies on the growth and structure of this kind of peculiar nanotubes due to their potential photocatalytic application[8-17].Recent studies have shown that the structures of titania nanotubes are complicated.The nanotube walls may not be TiO2.

A ZnO/rice husk-based hollow carbonaceous nanosphere composite as an anode for high-performance lithium-ion batteries

ZnO is considered as a substitute for the next generation of lithium ion battery anode materials because of its high volumetric energy density and abundant resources. In this work, we fabricate a new material that has nanorod-like ZnO distributed in a disorderly fashion on the surface of a rice husk-derived carbon skeleton. Rice husk as a carbon source is suitable for easing the pressure on the environment and improving the utilization of agricultural residues. Its unique interconnected hollow nanosphere structured skeleton provides better support for ZnO loading and electron transport. The ZnO/rice husk-based carbonaceous nanosphere composite samples were characterised by XRD, Raman, SEM and TEM. When used as an anode for lithium-ion batteries, the material exhibited promising Li storage properties and a high specific charge capacity of 920xa0mA h g−1 at 0.2C after 100 cycles.