Chunju Lv

The Effect of Composition Design on the Hydrolysis Reaction of Al−Li−Sn Alloy and Water

A new method of hydrogen generation from Al−Li−Sn alloy was studied in the present article. The hydrogen generation performance of the alloy could be regulated via composition design. The optimized Al−10 wt% Li−5 wt% Sn alloy yielded 1,329 ml g−1 hydrogen with 100% efficiency and controllable hydrogen generation rate within 30 min at 298 K. Using X-ray diffraction, scanning electron microscopy, and Brunauer-Emmet-Teller analysis, the improved hydrogen generation performance mostly came from the AlLi and Li13Sn5 phases distributed into Al matrix, which were helpful to decrease the particle size in the milling process. The phases acted as the initial reaction centers and stimulated Al hydrolysis in the hydrolysis process. There existed different hydrolysis processes, including chemical reaction of aluminum and water catalyzed by hydrolysis byproduct LiOH and electrochemical corrosion of Al and Li. The latter was based on the dual micro-galvanic cells between Al−Sn and Li−Sn from Al−Li13Sn5 microstructure. Al−Li−Sn alloys had a potential application in portable hydrogen sources due to its high hydrogen generation density, high hydrogen purity, etc. The experimental data laid a foundation for hydrogen generator design.

Enhanced cycling stability of spinel LiMn2O4 cathode by incorporating graphene sheets

LiMn2O4-graphene nanocomposites with different weight ratios of LiMn2O4/graphene were successfully prepared via a simple method by ball-milling of commercially available LiMn2O4 particles and graphene nanosheets. Experimental results revealed that the spinel LiMn2O4 particles within the as-prepared LiMn2O4-graphene nanocomposites were well distributed onto the flexible graphene sheets, and the nano-composites with a higher graphene content were favorable to form more uniform composite materials. Compared to the pristine spinel LiMn2O4 particles, the as-prepared LiMn2O4-graphene nanocomposites exhibited lower initial discharge capacities owing to the reduced amount of active materials (LiMn2O4 particles) in the nanocomposites. However, their electrochemical cycling performance was significantly enhanced, high-lighting the advantages of anchoring LiMn2O4 particles on graphene sheets. The enhanced cycling performance could be ascribed to the fact that the graphene nanosheets within the LiMn2O4-graphene nanocomposites could provide a 3D conducting scaffold, which could not only alleviate the aggregation of LiMn2O4 particles and accommodate the volume changes of LiMn2O4 particles, but also enhance the ionic conductivity and charge transfer during the lithiation/delifhiation process.

Polyaniline-coated selenium/carbon composites encapsulated in graphene as efficient cathodes for Li-Se batteries

In this work, we developed a polyaniline (PANI)-coated selenium/carbon nanocomposite encapsulated in graphene sheets (PANI@Se/C-G), with excellent performance in Li-Se batteries. The PANI@Se/C-G nanostructure presents attractive properties as cathode of Li-Se batteries, with a high specific capacity of 588.7 mAh·g–1 at a 0.2C (1C = 675 mA·g−1) rate after 200 cycles. Even at a high rate of 2C, a high capacity of 528.6 mAh·g–1 is obtained after 500 cycles. The excellent cycle stability and rate performance of the PANI@Se/C-G composite can be attributed to the synergistic combination of carbon black (as the conductive matrix for Se) and the double conductive layer comprising the uniform PANI shell and the graphene sheets, which effectively improves the utilization of selenium and significantly enhances the electronic conductivity of the whole electrode.

Facile Synthesis of Graphene–Enwrapped Ag3PO4 Composites with Highly Efficient Visible Light Photocatalytic Performance

In this work, thermally exfoliated graphene nanosheets (GNS) were employed to prepare novel Ag3PO4–GNS composite photocatalysts by a facile chemical precipitation approach. The as-prepared Ag3PO4–GNS composite photocatalysts were characterized by X-ray diffraction (XRD) pattern, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, thermogravimetric (TG) analysis, ultraviolet-visible diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectra. It was found that the Ag3PO4 particles were well deposited on the surfaces of GNS. Compared with bare Ag3PO4 and Ag3PO4–rGO composite, the Ag3PO4–GNS composite exhibited enhanced photocatalytic activity for the photodegradation of rhodamine B (RhB) under visible light irradiation. The photocatalytic degradation rate of Ag3PO4–GNS composite was 1.7 times that of bare Ag3PO4 and about 1.3 times that of Ag3PO4–rGO for the degradation of RhB. Furthermore, the photocatalytic stability of Ag3PO4–GNS composite was also greatly enhanced. This enhanced photocatalytic activity and stability could be ascribed to the positive synergetic effects between the Ag3PO4 particles and GNS sheets, which could provide a greater number of active adsorption sites, suppress charge recombination and reduce the serious photocorrosion of Ag3PO4. Moreover, the photocatalytic degradation of RhB over Ag3PO4–GNS composites was also optimized, suggesting that the optimal amount of GNS in the composites was 11.4wt.%. This work shows a great potential of Ag3PO4–GNS composite for environmental treatment of organic pollutants.

Hydrolysis Precipitation-assisted Solid-state Reaction to Li 4 Ti 5 O 12 and its Electrochemical Properties

Spinel lithium titanate (Li4Ti5O12) materials were synthesized by a hydrolysis precipitation-assisted solid-state method in the temperature range from 600 to 900 for large-scale production. DSC/TGA, XRD and SEM were used to characterize the as-prepared samples. The optimum synthesis condition was examined in relation to the charge–discharge performance. It was found that when the dry hydrolysis precipitation precursor with 8% Li excess was calcined at 700–800 for 12 h in air, a pure Li4Ti5O12 phase was obtained. The as-obtained material has the best electrochemical performance due to its narrow size distribution and precise stoichiometry of the oxide.