Puhong Wen

Dye-sensitized solar cells based on anatase TiO2 nanocrystals exposing a specific lattice plane on the surface

Dye-sensitized solar cells (DSCs) using anatase TiO2 nanocrystals exposing a specific lattice plane on the surface were studied. It was found that dye adsorption strongly depends on the lattice plane exposed on the TiO2 nanocrystal surface, which greatly affects DSC performance. TiO2 nanocrystals exposing mainly the (010) plane have a higher dye adsorption capacity and a higher Voc for DSC than normal spherical nanocrystals. TiO2 nanocrystals with a large adsorption constant Kad can yield a high Jsc. The highest Jsc (20.6 mA/cm2) was achieved by using TiO2 nanocrystals with the specific lattice plane on the surface.Dye-sensitized solar cells (DSCs) using anatase TiO2 nanocrystals exposing a specific lattice plane on the surface were studied. It was found that dye adsorption strongly depends on the lattice plane exposed on the TiO2 nanocrystal surface, which greatly affects DSC performance. TiO2 nanocrystals exposing mainly the (010) plane have a higher dye adsorption capacity and a higher Voc for DSC than normal spherical nanocrystals. TiO2 nanocrystals with a large adsorption constant Kad can yield a high Jsc. The highest Jsc (20.6 mA/cm2) was achieved by using TiO2 nanocrystals with the specific lattice plane on the surface.

Relationships between Cell Parameters of Dye-Sensitized Solar Cells and Dye-Adsorption Parameters

The performance of dye-sensitized solar cells (DSCs) is affected strongly by sensitizer-dye adsorption behavior on TiO(2) nanocrystal electrode. This study reports quantitative relationships between DSC cell performance parameters and dye-adsorption parameters for the first time. We discovered a logarithmic relationship between short-circuit photocurrent density (J(sc)) and dye-adsorption equilibrium constant on TiO(2) surface, and a linear relationship between open-circuit potential (V(oc)) and dye-adsorption density on TiO(2) surface for DSCs. These relationships provide a convenient method for forecasting the performance of TiO(2) nanoparticles for DSCs from the dye-adsorption parameters, and also indicate future directions for the development of high-performance TiO(2) nanoparticles for DSCs.

Soft chemical in situ synthesis, formation mechanism and electrochemical performances of 1D bead-like AgVO3 nanoarchitectures

The soft chemical process is a useful and unique method for the preparation and design of one-dimensional (1D) nanoarchitectures. 1D bead-like AgVO3 nanoarchitectures are prepared via a soft chemical in situ reaction using the layered structure K2V6O16·2.7H2O platelike particles as the precursor. The formation mechanism is investigated through tracing the evolution of the structure and morphology of intermediate products during the reaction, and it consists of two processes. One is the in situ reaction of the Ag+ ions with the V3O8 layers of K2V6O16. The other is the fragmentation of the 2D platelike composite into a 1D fiber composite. Moreover, the electrochemical investigation shows that after 50 cycles at a current density of 100 mA g−1, the 1D bead-like nanostructure cathode exhibits a higher discharge capacity (127 mA h g−1) than that of 1D nanowires (75 mA h g−1), mainly due to the larger specific surface area and fine particles-constructed architecture.

Topotactic synthesis and photocatalytic performance of one-dimensional ZnNb2O6 nanostructures and one-dimensional ZnNb2O6/KNbO3 hetero-nanostructures

This paper introduces one-dimensional ZnNb2O6/KNbO3 hetero-nanostructures and one-dimensional ZnNb2O6 nanostructures. These nanostructures are synthesized via in situ topotactic structural transformation reaction using the tunnel structure K2Nb2O6 filiform crystal as precursor. Firstly, Zn2+ ions intercalate into K2Nb2O6 crystal by exchanging K+ ions from the K2Nb2O6 crystal with Zn2+ from Zn(NO3)2 or Zn(CH3COO)2 aqueous solution, to form two different Zn2+-exchanged samples, and then these Zn2+-exchanged samples topotacticly transform into one-dimensional ZnNb2O6/KNbO3 hetero-nanostructures and ZnNb2O6 nanostructures during heat-treatment. The formation reaction and structure of these samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and energy-dispersive spectroscopy (EDS). Photocatalytic experiments showed that one-dimensional ZnNb2O6/KNbO3 hetero-nanostructures and ZnNb2O6 nanostructures have excellent photocatalytic performance for the degradation of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO).

Controllable synthesis and morphology evolution from two-dimensions to one-dimension of layered K2V6O16·nH2O

A two-dimensional (2D) layered K2V6O16·2.7H2O platelike single crystal was successfully synthesized in a short time of 3 h via a simple hydrothermal method. The number of H2O molecules and the morphology of the layered K2V6O16·nH2O hexavanadate crystal can be easily controlled by adjusting the pH value of the system and the reaction time used for the hydrothermal process. By studying the structure and morphology of hexavanadate samples obtained at different reaction times under acid conditions using an X-ray diffractometer (XRD), a field emission scanning electron microscope (FE-SEM) and a transmission electron microscope (TEM), it can be concluded that the 2D layered K2V6O16·2.7H2O platelike single crystal hexavanadate gradually evolves into a one-dimensional (1D) layered K2V6O16·1.5H2O fiberlike single crystal hexavanadate during the hydrothermal process as the reaction time is prolonged. In addition, the photocatalytic performance of the as-prepared products was explored.

Screening of Inorganic Adsorbents for Selective Adsorption of Thiophene from Model Gasoline

Hydrodesulfurization-treated (HDS-treated) gasoline with low sulfur content is an important source of primary fuel for fuel cells, although it contains sulfur compounds, thiophene (TP), benzothiophene (BTP), and thiophene alkylated derivatives, known as a poison for the reformer catalysts and the electrode catalysts of fuel cells. Adsorptive removal of TP from model organic liquid of HDS-treated gasoline was screened on different kinds of inorganic adsorbents: hydrous metal oxides, mixed metal oxides, aluminosilicates, acidic salts of multivalent metal, hetero polyacidic salt, and metal salts of iron hexacyanate. All the adsorbents showed very low TP uptake, less than 5% of the total TP amount when metal ions were not loaded on the adsorbent. On the other hand, some metal ion (Ag, Cu, and Ce) loaded adsorbents had good TP adsorptive properties. On simple metal oxides, Ag ion was better for the formation of adsorption center than Ce or Ni ions. In zeolite group, Ce-loaded Y-zeolite showed the largest TP uptake (99% of the total TP amount). Hydrous cerium oxide and the Ce-loaded adsorbents prepared from K4[Fe(CN)6], Silicagel, TiO2, and ZrO2 did not show TP selectivity. The effect of coexisting toluene on TP adsorption was studied from the TP solutions with and without toluene.

Structural and morphological evolution of an octahedral KNbO3 mesocrystal via self-assembly-topotactic conversion process

Different morphologies of potassium niobates were prepared via a novel two-step solvothermal process. Firstly, a precursor polyion solution of [Nb6O19]8− was prepared. Secondly, the different morphologies of potassium niobates were prepared by solvothermal treatment of the polyion solution in different water–organic solvents and adjusting the composition of the solvents. A meaningful KNbO3 (KN) mesocrystal with octahedral morphology was generated for the first time using propylamine as the solvent. The as-obtained KN mesocrystal was a polycrystal constructed from uniform [110]-crystal-axis-oriented KN nanocube crystals, which show a set of single-crystal-like electron diffraction spots. The KN mesocrystal was formed via a self-assembly-topotactic conversion mechanism including the self-assembly of plate-like particles, topotactic conversion to the KN structure and mesocrystalline crystal growth of KN nanocrystals. Such mesocrystal displays a higher piezoelectric response than common individual perovskite crystals. The success in developing the KN mesocrystal can be easily applied to the preparation of a series of piezoelectric K1−xNaxNbO3 continuous solid solution mesocrystals.

The nonlinear optical properties of the nanohybrid thin film forming by intercalating methylene blue dye into layered titanate nanosheets

Solid-state dye-doped materials are an attractive alternative to conventional liquid dye solution. In this study, the spectral characteristics and the nonlinear optical properties of dye methylene blue before and after intercalating into layered titanate nanosheets and forming a nanohybrid thin film were investigated by measuring the absorption and fluorescence spectra and using single beam z-scan technique under irradiation of low power continuous wave (CW) produced by He-Ne laser with a wavelength of 632.8 nm and DPSS laser with a wavelength of 532 nm, respectively. The nonlinear experimental results show that the MB/HTO nanohybrid thin film has a negative nonlinear refractive index under irradiation by He-Ne laser, but it reverses to positive value by DPSS laser.