Benxia Li

Ultrasonic-spray-assisted synthesis of metal oxide hollow/mesoporous microspheres for catalytic CO oxidation

Transition metal oxides with hollow or mesoporous microstructures represent a unique class of heterogeneous catalysts or catalyst supports with many fascinating features such as the large surface areas, tunable pore sizes and volumes, multitude of compositions, and ease of functionalization. In this work, we demonstrated a general ultrasonic-spray-assisted synthesis of various transition metal oxide hollow/mesoporous microspheres, using only low-cost commercial metal chlorides as precursors and water as solvent. As typical examples, five mono-component metal oxides (CeO2, α-Fe2O3, Co3O4, SnO2 and TiO2) hollow or mesoporous microspheres were prepared and their formation mechanisms were discussed. The catalytic carbon monoxide (CO) oxidation indicated that these metal oxide products exhibited improved catalytic activities than some of those reported previously, due to their tiny crystalline grains, large pore volume and specific surface area. The universality of this synthetic method was also demonstrated in producing multi-component and multi-functional metal oxides with hollow/mesoporous structures. This work therefore provides an industrial level producing method for the scalable preparation of various metal oxide hollow/mesoporous microspheres which are expected to be used as high-performance catalysts or catalyst supports in more chemical reactions.

A flexible nanofiber-based membrane with superhydrophobic pinning properties

A nanofiber-based TiO2(B)/carbon nanofiber membrane has been synthesized by a facile and effective route that incorporates electrospinning approach with hydrothermal method. The prepared membrane shows high flexibility and hydrophilicity. After treatment with a low surface energy fluorosilane, the obtained superhydrophobic surface endows the membrane a high adhesive force due to the hybrid microstructure of TiO2(B) nanotubes and nanoplates on fibers. A water droplet on the surface of the membrane appears spherical in shape, which cannot roll off even when the membrane is bent and turned upside down. When a water droplet dropped from a certain height above the tilt membrane, the rolled water droplet can be stopped after a small displacement. In addition, a 12 μl water droplet can be quickly captured from a hydrophobic surface by curvature change of the superhydrophobic TiO2(B)/carbon nanofiber membrane. The membrane with excellent static and dynamic pinning performance to water may be expected to apply to biomedical and microfluidic devices.

Synthesis of Metal-Oxide/Carbon-Fiber Heterostructures and Their Properties for Organic Dye Removal and High-Temperature CO 2 Adsorption

One-dimensional metal-oxide/carbon-fiber (MO/CF) heterostructures were prepared by a facile two-step method using the natural cotton as a carbon source the low-cost commercial metal salts as precursors. The metal oxide nanostructures were first grown on the cotton fibers by a solution chemical deposition, and the metal-oxide/cotton heterostructures were then calcined and carbonized in nitrogen atmosphere. Three typical MO/CF heterostructures of TiO2/CF, ZnO/CF, and Fe2O3/CF were prepared and characterized. The loading amount of the metal oxide nanostructures on carbon fibers can be tuned by controlling the concentration of metal salt in the chemical deposition process. Finally, the performance of the as-obtained MO/CF heterostructures for organic dye removal from water was tested by the photocatalytic degradation under a simulated sunlight, and their properties of high-temperature CO2 adsorption were predicted by the temperature programmed desorption. The present study would provide a desirable strategy for the synthesis of MO/CF heterostructures for various applications.

Synthesis, Adsorptive, and Photocatalytic Properties of Carbon Nanotubes/TiO 2 Nanocomposite Photocatalysts

The carbon nanotubes/TiO2 (CNTs/TiO2) composite photocatalysts composed of TiO2 nanoparticles and multiwalled carbon nanotubes (CNTs) were prepared by a facile hydrothermal method. The photocatalysts were characterized by a range of analytical techniques including X-ray powder diffraction, field emission scanning electron microscope, thermal gravimetric analysis and UV–Vis optical absorption spectra, etc. The amount of TiO2 nanoparticles growing on CNTs could be tuned by adjusting the dosage of precursor in the reaction solution. Both the adsorptivity and photocatalytic activities of pure CNTs, pure TiO2, and the CNTs/TiO2 nanocomposites were tested by the removal of methylene blue from water in dark and under a simulated sunlight, respectively. By comparison, the improved photocatalytic activity of the CNTs/TiO2 nanocomposite is mainly due to that the CNTs can disperse the active component of TiO2 nanoparticles, provide a larger the specific surface area, as well as act as an electron sink to accelerate the separation of the photogenerated charges.