Sheng-qi Guo

Mesoporous Ni0.85Se Nanospheres Grown in Situ on Graphene with High Performance in Dye-Sensitized Solar Cells

Mesoporous Ni0.85Se nanospheres grown on graphene were synthesized via the hydrothermal approach. Because of the exceptional electron-transfer pathway of graphene and the excellent catalytic ability of the mesoporous Ni0.85Se nanospheres, the nanocomposites exhibited excellent electrocatalytic property as the counter electrode (CE) of dye-sensitized solar cells. More catalytic active sites, better charge-transfer ability and faster reaction velocity of Ni0.85Se@RGO (RGO = reduced graphene oxide) CE led to faster and more complete I3(-) reduction than Pt, Ni0.85Se, and RGO CEs. Furthermore, the power conversion efficiency of Ni0.85Se@RGO CE reached 7.82%, which is higher than that of Pt CE (7.54%). Electrochemical impedance spectra, cyclic voltammetry, and Tafel polarization were obtained to demonstrate positive synergetic effect between Ni0.85Se and RGO, as well as the higher catalytic activity and the better charge-transfer ability of Ni0.85Se@RGO compared with Pt CE.

Facile preparation of hierarchical Nb2O5 microspheres with photocatalytic activities and electrochemical properties

Hierarchical flower-like Nb2O5 microspheres have been prepared via a facile hydrothermal approach without any additives. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to clarify the structure and morphology of the Nb2O5 microspheres. Structure and morphology evolution mechanisms have been proposed for the hierarchical structure in detail. During the symmetric Ostwald ripening, the resultants formed aggregates composed of two-dimensional nanoflakes as building blocks. Photocatalytic activity of the as-prepared Nb2O5 microspheres was evaluated by the photodegradation of Rhodamine B (RhB), and over 90% of RhB was degraded within 30 min under the irradiation of UV light. The as-prepared Nb2O5 exhibits higher photocatalytic activity than commercial Degussa P25. Moreover, Nb2O5 was tested as an anode material of lithium-ion batteries, which displayed high reversibility and excellent rate stability at a current density of 50 mA g−1.

Controlled fabrication of hierarchical WO3·H2O hollow microspheres for enhanced visible light photocatalysis

WO3·H2O nanostructures have been prepared through a facile hydrothermal route by controlling their morphology during synthesis. WO3·H2O nanoplates with a thickness of ∼45 nm and hierarchical hollow microspheres (HMSs) structures could be obtained by introducing different amounts of citric acid. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to understand the structure and morphology of the two types of WO3·H2O. The formation mechanisms for WO3·H2O nanoplates and WO3·H2O HMSs were investigated. The photocatalytic activities, determined by rhodamine B (RhB) degradation under visible light irradiation of WO3·H2O HMSs photocatalysts, were significantly improved as compared with WO3·H2O nanoplates. The higher efficiency of photocatalytic activity in WO3·H2O HMSs was attributed to its higher surface-to-volume ratio and stability against aggregation. In addition, we investigated the toxicity of WO3·H2O HMSs against an important model fungus, yeast (Saccharomyces cerevisiae). The results indicate that the as-synthesized hierarchical WO3·H2O HMSs could be used as a green and efficient photocatalyst.

Ultralong In2S3 Nanotubes on Graphene Substrate with Enhanced Electrocatalytic Activity.

Ultralong one-dimensional (1D) nanostructures including nanowires or nanotubes have been extensively studied because of their widespread applications in many fields. Although a lot of methods have been reported to prepare In2S3 nanotubes, approaching these nanotubes through one-pot solution synthesis is still extremely difficult, probably because of the intrinsic isotropic crystal growth characteristic of In2S3. In this article, we demonstrated a self-assembly approach for hydrothermal synthesis of In2S3 nanotubes/graphene composites, which contain ultralong (up to 10 μm) In2S3 nanotubes on graphene substrate. The influence of several important synthetic parameters on the final products has been systematically investigated. Importantly, the as-prepared In2S3 nanotubes/graphene composites can be easily cast on FTO to form a film, which can be used as a counter electrode. Our research indicates that the as-fabricated counter electrode exhibits excellent electrocatalytic activity toward the iodide species (I-/I3-) reduction reaction and very high energy conversion efficiency (8.01%) in dye-sensitized solar cells.

Synthesis of NiSe2/reduced graphene oxide crystalline materials and their efficient electrocatalytic activity in dye-sensitized solar cells

We synthesized two kinds of NiSe2 crystalline material grown on graphene (microsphere NiSe2/RGO and octahedron NiSe2/RGO) through a facile hydrothermal route. Their catalytic activities as the counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) were investigated through I–V curves and conversion efficiency tests. Attributed to the outstanding carrier transfer properties of graphene nanosheets, the NiSe2/graphene materials exhibited an excellent electrochemical performance, and microsphere NiSe2/RGO showed a better electrocatalytic performance as the CE for the reduction of triiodide than that of Pt. Furthermore, Tafel polarization and electrical impedance spectroscopy (EIS) were performed to evaluate the electrocatalytic activity of the as-prepared CEs.

In2O3 cubes: synthesis, characterization and photocatalytic properties

3D cubic microporous In2O3 has been successfully obtained by calcining the as-synthesized cube In(OH)3–InOOH precursor at 300 °C for 2 hours. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to clarify the structures and morphologies of both the cubic In(OH)3–InOOH precursor and cubic In2O3. The formation mechanisms of the In(OH)3–InOOH precursor and cubic In2O3 were investigated. As an important semiconductor photocatalytic material, its photocatalytic properties have been tested. Under the irradiation of UV light, the cubic microporous In2O3 exhibits excellent photocatalytic properties to degrade eosin B (EB), which presents ∼95% degradation of EB after 3 hours and the degradation rates is 10.5 times that of commercial In2O3 powder. The high separation efficiency of electron–hole pairs results in high photocatalytic activity. Furthermore, the photoluminescent properties of the cubic microporous In2O3 have been investigated as well.