Youwei Yan

Sol–gel combustion synthesis of nanocrystalline LaMnO3 powders and photocatalystic properties

A novel LaMnO3 photocatalyst with perovskite structure was prepared by sol–gel combustion method. The combustion reaction mechanisms of nanocrystalline LaMnO3 powders were investigated by thermal analysis, infrared spectra, and X-ray diffraction technique. The results showed that the gels exhibited self-propagating behavior after ignition in air. Nanocrystalline LaMnO3 powders can be synthesized in one step by using sol–gel combustion synthesis. The photocatalytic activity of the LaMnO3 powders were evaluated by degradation of methyl orange (MO) in water under UV light irradiation. The results showed that the LaMnO3 powders exhibit good photocatalytic activities under UV light irradiation. The degradation percentage after 36xa0h on LaMnO3 powders was about 76%.

Ultrasonic-assisted solution combustion synthesis of porous Na3V2(PO4)3/C: formation mechanism and sodium storage performance

AbstractSolution combustion synthesis (SCS) is an effective and rapid method for synthesizing nanocrystalline materials. However, the control over size, morphology, and microstructure are rather limited in SCS. Here, we develop a novel ultrasonic-assisted solution combustion route to synthesize the porous and nano-sized Na3V2(PO4)3/C composites, and reveal the effects of ultrasound on the structural evolution of NVP/C. Due to the cavitation effects generated from ultrasonic irradiation, the ultrasonic-assisted SCS can produce honeycomb precursor, which can be further transformed into porous Na3V2(PO4)3/C with reticular and hollow structures after thermal treatment. When used as cathode material for Na-ion batteries, the porous Na3V2(PO4)3/C delivers an initial discharge capacity of 118xa0mAhxa0g−1 at 0.1 C and an initial coulombic efficiency of 85%. It can retain 93.8% of the initial capacity after 120xa0cycles at 0.2 C. The results demonstrate that ultrasonic-assisted SCS can be a new strategy to design crystalline nanomaterials with tunable microstructures.n Graphical abstractPorous and nano-sized Na3V2(PO4)3/C composites with reticular and hollow structures are synthesized by an ultrasonic-assisted solution combustion route due to the cavitation effects, and exhibit excellent electrochemical performance as cathode in sodium ion battery.

Hydrothermal synthesis of bismuth sodium titanate particles with different morphologies

Nanostructured Na0.5Bi0.5TiO3 particles have been synthesized by a hydrothermal synthesis method using a layered titanate H1.07Ti1.73O4·nH2O as a Ti precursor. The obtained Na0.5Bi0.5TiO3 particles showed different morphologies including plate-like, wire-like, and cubic-like structures in different hydrothermal conditions. The effect of the NaOH concentration on the growth and morphology evolution of hydrothermally derived Na0.5Bi0.5TiO3 powders were investigated. It was found that alkaline concentration had a great effect on the phase and morphology of the resultant powders. The dissolution–recrystallization and in situ topotactic transformation mechanisms were suggested in different alkaline concentrations according to the evolution process.

Effects of reaction parameters on solution combustion synthesis of lepidocrocite-like K0.80Ti1.733Li0.267O4: phase formation and morphology evolution

A lepidocrocite-like potassium lithium titanate K0.80Ti1.733Li0.267O4 (KLTO) with layered structure was synthesized by an auto-igniting solution combustion method using glycine and metal (Ti, K and Li) nitrate as reactants. The crystalline structure and morphology of the as-prepared product were examined using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Effects of reaction parameters such as ignition temperature and oxidizers to fuel ratio on the phase formation and morphology evolution are investigated in this paper. A pure phase of KTLO was obtained at a low temperature (650xa0°C) within several minutes. Excessive glycine added into the aqueous precursor solution facilitated the synthesis of a pure and well-crystallized product. As-prepared particles exhibited plate-like shape with a length of 5–20xa0μm and a thickness of about 2xa0μm. No residual organic compound existed in the product. After the as-prepared product was post solution combustion heat-treated (1100xa0°C for 2xa0h), the particles became uniform in size with smooth surface and well-defined crystalline structure. The product exhibited excellent ion-exchange, intercalation, and exfoliation properties. The exfoliated titania nanosheets are characterized by high two-dimensional anisotropy with a thickness of about 20xa0nm and a lateral size ranging from sub-micrometers to several tens of micrometers.

Graphene-induced growth of single crystalline Sb2MoO6 sheets and their sodium storage performance

A single crystalline molybdenum antimony oxide (Sb2MoO6) sheet/reduced graphene oxide (RGO) composite is reported for the first time, for use as an anode for a sodium ion battery with excellent cyclability and rate performance. The addition of graphene oxides in the hydrothermal synthesis can not only induce the tabular growth of Sb2MoO6 single crystals but also serves as a conductive network in the electrochemical reactions. The Sb2MoO6/RGO composite exhibits a capacity of 430 mA h g−1 at 0.05 A g−1 and maintains 270 mA h g−1 at a high current density of 4 A g−1. A capacity retention of 93.2% can be acquired after 220 cycles at 0.2 A g−1. In situ X-ray diffraction, ex situ transmission electron microscopy and X-ray photoelectron spectroscopy reveal a conversion reaction in the initial cycle of the Sb2MoO6/RGO composite. Thus, the reversible capacity is mainly imparted by the alloying/dealloying reactions of the antimony element, while amorphous molybdenum oxide (MoOx) and sodium oxide (Na2O) composites serve as the buffer matrix.