Pengqi Chen

Combustion synthesis and excellent photocatalytic degradation properties of W18O49

In this paper, one-dimensional W18O49 nanopowders were fabricated by a one-step solution combustion method using glycine as the fuel and a metal acid radical ion as the metal source. The morphologies and non-stoichiometric single-crystal phase of W18O49 can be controlled by changing the amount of the fuel. The nanoneedles had a large amount of defects such as oxygen vacancies. This characteristic resulted in an excellent visible light-driven photocatalytic performance that took about 50 min to degrade methylene blue (100 mL; 40 mg L−1) under visible light. The interesting reaction mechanism of such needle-like W18O49 and the photocatalytic mechanism are studied in this paper.

Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Superior optical properties of Fe3+–W18O49 nanoparticles prepared by solution combustion synthesis

Modification by metal-doping allows the design of new nanomaterials with enhanced optical properties. In this paper, the photocatalytic effects of Fe3+-doped W18O49 nanorods prepared by solution combustion synthesis were studied for the first time. The Fe3+-doped W18O49 powders were investigated by X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. The powders were well-crystalline with diameters ranging from 50 nm to 250 nm and the length decreasing from more than 10 μm to 4 μm on average. The photoluminescence (referred to as PL here after) spectrum showed that the emission intensity increased with increasing Fe3+ doping, suggesting that more defects were generated. Moreover, this novel composite catalyst displayed excellent photocatalytic efficiency towards the degradation of organic compounds in aqueous media under UV-visible light irradiation. In particular, 0.5 wt% Fe3+-doped W18O49 had the best photocatalytic efficiency. This improvement was mainly attributed to the synergistic effect between Fe3+ and W18O49 nanopowders and the defects in the nanostructure caused by doping.

Solution combustion synthesis of nanosized WOx: characterization, mechanism and excellent photocatalytic properties

Various nanoscale tungsten oxides with excellent photocatalytic properties were synthesized via an ultra-rapid solution combustion synthesis method. The results indicated that the WO3 and W18O49 could be synthesized with different fuels (glycine, urea, urea and citric acid) and the powders presented mesoporous structures with different morphologies such as nanoparticles, nanorods and nanoneedles. Detailed reaction mechanisms of various systems were identified, and the specific roles of different fuels were discussed. Moreover, the synthesized powders displayed excellent photocatalytic efficiency, degrading organic compounds in 50 min under UV-visible light irradiation. The work suggests that solution combustion synthesis can be used as a new strategy to design nanosized stoichiometric and oxygen-vacancy-rich nonstoichiometric oxides with excellent properties.

The formation of CuO porous mesocrystal ellipsoids via tuning the oriented attachment mechanism

We report a new chemical reaction route to synthesizing CuO porous mesocrystal ellipsoids via decomposition of copper vanadium oxide under hydrothermal conditions. By finely tuning the oriented attachment growth mechanism of CuO, a porous mesocrystal structure was synthesized. Structural and morphological evolutions of the CuO product were investigated and the formation of CuO porous mesocrystal ellipsoids here was essentially determined by the amount of ammonium metavanadate. An oriented nanoparticle aggregation with tailoring of the structure, including compact mesocrystals and porous mesocrystals, could be achieved in different concentrations of reactants. The strategy of constructing the structure via an oriented attachment growth mechanism could be applied to the synthesis of other nanomaterials with complex structures.