Dingning Ke

Synthesis of floriated ZnFe2O4 with porous nanorod structures and its photocatalytic hydrogen production under visible light

Floriated ZnFe2O4 with porous nanorod structures were successfully synthesized via mild hydrothermal and calcination processes by using cetyltrimethylammonium bromide (CTABr) as a template-directing reagent. The resulting ZnFe2O4 was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS) and nitrogen adsorption measurement. It was found that the floriated ZnFe2O4 nanostructures were composed of porous nanorods with an average length of 122 nm and diameter of 29 nm. The obtained ZnFe2O4 with a bandgap of ∼1.94 eV was firstly used as a visible-light-driven photocatalyst for hydrogen production, and exhibits remarkable photostability in an aqueous suspension by using CH3OH as a sacrificial reagent. Moreover, the possible photo-reaction mechanism for the hydrogen production from CH3OH aqueous solution was proposed for better understanding the photocatalytic behavior of ZnFe2O4 without Pt-loading.

Effects of Hydrothermal Temperature on the Microstructures of BiVO4 and Its Photocatalytic O2 Evolution Activity under Visible Light

Microspheric and lamellar BiVO(4) powders were selectively prepared through a hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as a template-directing reagent. The as-prepared BiVO(4) powders were characterized by X-ray diffraction, electron microscopy, nitrogen adsorption-desorption experimentation, Fourier transform infrared spectrometry, and UV-vis diffuse reflectance spectroscopy. Experimental results indicate that microspheric BiVO(4) with particle sizes in the range of 7-12 microm can be derived from a relatively low hydrothermal temperature (<or=160 degrees C) and possess a mixed crystal consisting of tetragonal and monoclinic phases, whereas lamellar BiVO(4) with a pure monoclinic phase can be obtained at a higher hydrothermal temperature (200 degrees C). Their photocatalytic activities for O(2) evolution were investigated by using Fe(NO(3))(3) as a sacrificial reagent under visible-light irradiation, and the lamellar BiVO(4) shows a better photoactivity than the microspheric product due to its pure monoclinic crystal phase. Moreover, the effects of CTAB content on the morphologies and crystal phases of the obtained products were also discussed. It was found that the addition of CTAB can adjust the morphologies of BiVO(4) and obstruct the crystal phase transformation from the mixed crystal to pure monoclinic BiVO(4) during the hydrothermal process.

Photocatalytic hydrogen generation using a nanocomposite of multi-walled carbon nanotubes and TiO2 nanoparticles under visible light irradiation

Nanocomposite catalysts (MWNT-TiO(2)) were prepared hydrothermally from multi-walled carbon nanotubes (MWNTs) and titanium sulfate as the titanium source, and then systematically analyzed using electron microscopy, Raman, FT-IR, and UV-vis spectroscopy. Pt-loaded nanocomposites, pristine TiO(2) and MWNTs were examined for their photocatalytic activity on splitting water with triethanolamine as an electron donor. Under visible light irradiation (lambda>420 nm), hydrogen was successfully produced over the Pt/MWNT-TiO(2), while no capacity to split water showed on the Pt-loaded pristine TiO(2) and MWNTs. Under full spectral irradiation of a Xe-lamp, a hydrogen generation rate of up to 8 mmol g(-1) h(-1) or more was achieved. The significant photocatalytic activity of the nanocomposites was attributed to the synergetic effect of the intrinsic properties of its components such as an excellent light absorption and charge separation on the interfaces between the modified MWNTs and TiO(2), resulting from direct growth of TiO(2) nanoparticles on the surface of the MWNTs during the hydrothermal process.

Photosensitization of Ruthenium(II) Complex on Titania for Photocatalytic H2 Evolution Under Visible-Light Irradiation

Hydrogen production over dye-sensitized Pt/P25 under visible-light irradiation was investigated by using methanol or TEOA as an electron donor. The binuclear Ru(II) dye (Ru2 (bpy)4 L1 -PF6 ) shows the best photosensitization in both sacrificial reagent solutions due to its larger conjugation system and “antenna effect”, which is loosely linked with TiO2 and exhibits more steady and higher increases in H2 evolution upon prolonging the irradiation time in comparison with the tightly linked N719. The dynamic equilibrium between the linkage of ground dye and divorce of oxidized dye from TiO2 can enhance the electron injection and hinder the backward transfer, and then improve the H2 evolution efficiency.Copyright