Xiangyan Wang

Effective electron collection in highly (110)-oriented ZnO porous nanosheet framework photoanode

A highly (110)-oriented ZnO porous nanosheet framework is designed as the photoanode in photoelectrochemical systems, by virtue of its anisotropic electronic properties. It can be facilely prepared in large scale via a hydrothermal method. X-ray diffraction (XRD) analyses show that the orientation index of the (110) diffraction plane is 3.54, indicating the films possess (110) preferred orientation. Field-emission scanning electron microscope (FE-SEM) images exhibit that most of the nanosheets stand nearly perpendicularly on the substrate. The {002} lattice planes work just like conducting wires and induce the electrons to transport to the substrate. Chronoamperometry measurement demonstrates an effective electron collection. When the nanostructured photoanode is introduced to dye-sensitized solar cells, a conversion efficiency of 3.7% is obtained. The photoanode also has potential application in the other photoelectrochemical systems, such as photocatalytical splitting of water.

Multilayer structure with gradual increasing porosity for dye-sensitized solar cells

Multilayer structure was prepared in a dye-sensitized solar cell work electrode by enlarging the porosity in each layer being coated on the fluorine-doped tin oxide transparent conducting glass from bottom to top. The multilayer structure exhibits an improved light scattering character, which resulted in better light harvesting of the cell. An obvious improvement in short circuit current is obtained. I-V characteristic measurement indicates an improved efficiency by 13% as compared to homogeneous pore-size samples. Diffuse reflectance spectra, scanning electron microscope images, and porosity measurements demonstrate that larger porosity is the cause of enhanced light scattering.

ZnO plates synthesized from the ammonium zinc nitrate hydroxide precursor

ZnO assembled hexagonal or porous rectangular plates were synthesized from the decomposition of a new precursor, ammonium zinc nitrate hydroxide (NH4Zn3(OH)6NO3), through a facile solvothermal route assisted by Poly(styrene sulfonic acid) sodium salt (PSS). XRD, BET surface area measurements, SEM, HRTEM and TG-DSC were used to describe the as-prepared products and understand the phase transformation. Our results indicate that the morphology of the ZnO plates is dependent strongly on the decomposition process of the precursor. By directly heating NH4Zn3(OH)6NO3, porous ZnO plates were obtained due to the thermal decomposition of the precursor. Using the same precursor under the solvothermal reaction, however, the final product is hexagonal ZnO plates. The growth mechanism of ZnO plates formed in different synthetic routes was proposed. Photoluminescence (PL) and photocatalytic properties of the as-prepared ZnO with different morphologies were studied. Porous ZnO plates showed three emission peaks, which may be induced by its microstructure and defect centres, and the porous ZnO showed the improved photocatalytic activity for photoreduction of CO2.

Solvothermal synthesis of monodisperse iron oxides with various morphologies and their applications in removal of Cr(VI)

Monodisperse iron oxide micro-, nanospindles and nanospheres with controlled sizes were synthesized through a facile solvothermal process. The products are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area measurements, scanning electron microscopy and high-resolution transmission electron microscopy. The growth mechanism of spindle-like or spherical iron oxides with controlled size is discussed. Different content of Cl− in the reaction medium can also influence the nucleation rate through the decomposition of Fe8O8(OH)8Cl1.35 and thus control the particle sizes. The as-prepared iron oxides exhibit size dependence in their physical properties such as UV-vis absorption spectra and IR spectra. In addition, the removal capacities of Cr(VI) of the as-prepared iron oxides are investigated. The better performances of the as-prepared iron oxides than commercial iron oxides could be attributed to the larger surface area and rough surface structure.

Influence of measurement parameter on dye-sensitized solar cell efficiency

The testing time interval and voltage interval in accurately measuring the efficiency of Dye-sensitized solar cells is discussed abased on experiments and quantitative analysis. By measuring a typical dye-sensitized solar cell which was characterized with the crystalline ingredient, holes, and interface, the influences of testing time interval and voltage interval to the measured I–V curve were lay out, that the measured efficiency results fluctuated from 6.02% to 15%. Its found in experiment that both different testing time interval and voltage interval leaded to fluctuations of measured efficiency and even got much higher measured efficiency value than that in steady work state, while no such phenomena were observed in that of silicon cells. By farther analysis, the scan speed, which is the combine of the time interval and voltage interval, was attributed as the factor of influence to the measured result. According to the experimental results, the range of measurement parameters for accurate efficiency of DSSC was given.