Yali Cao

Facile synthesis of Bi2S3 hierarchical nanostructure with enhanced photocatalytic activity.

A simple wet chemistry method was employed for the synthesis of Bi2S3 hierarchical nanostructure using thioglycolic acid as a capping agent under reflux condition. The obtained products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscope images (HR-TEMs), energy dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR), and nitrogen sorption measurement. FE-SEM and TEM observations displayed that Bi2S3 hierarchical nanostructure assembled from nanorods of about 100 nm in length and 5-10 nm in diameter was successfully obtained. The photocatalytic activity of the as-prepared samples was evaluated by the photocatalytic degradation of methyl orange under UV irradiation. The results indicated that Bi2S3 hierarchical nanostructure exhibited superior photocatalytic performance to pure Bi2S3, which can be ascribed to large specific surface area, hierarchical nanostructure, and high hydrophilicity.

A room-temperature solid-state route for the synthesis of graphene oxide–metal sulfide composites with excellent photocatalytic activity

A simple and high yield room-temperature solid-state method was employed for the first time to fabricate graphene oxide–metal sulfide composites (GO–metal sulfide composites). The chemical composition, morphology and microstructural features of the obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen absorption–desorption specific surface area (BET) and UV-vis spectroscopy (UV). TEM study indicates that metal sulfide nanoparticles were well dispersed on the GO nanosheets in the GO–metal sulfide composites. It was found that the specific surface area of the composites increased with the introduction of GO. The as-synthesized GO–metal sulfide composites were used as photocatalysts for the degradation of methyl orange (MO) under UV irradiation. The results indicated that the composites exhibited superior photocatalytic activity to pure metal sulfides, owing to the high specific surface area and the reduction of photoinduced electron–hole pair recombination in metal sulfides due to the introduction of GO.

Solid-state synthesis of SnO2–graphene nanocomposite for photocatalysis and formaldehyde gas sensing

A facile solid-state synthetic route has been developed to prepare a tin oxide–graphene (SnO2–graphene) nanocomposite. Graphene decorated with tin oxide (SnO2) nanoparticles was synthesized by in situ solid-state chemical reaction at room temperature. The obtained SnO2–graphene nanocomposite has been investigated for applications as a photocatalyst to degrade organic contaminants in water and a chemical sensor to detect various vapours. The experiment results show that the SnO2–graphene nanocomposite exhibited improved performances for photocatalytic decomposition of Methyl Orange and Rhodamine B, and formaldehyde sensing comparable with the SnO2 nanoparticles. The enhancement of properties is proposed to be related to the large specific surface area of the nanocomposite and the good electronic characteristics of graphene.

A general strategy for synthesis of metal nanoparticles by a solid-state redox route under ambient conditions

A general strategy has been developed to synthesize metal nanoparticles by solid-state redox reaction under ambient conditions. A series of metallic nanoparticles, such as Ni, Fe, Sn, Co nanoparticles, and bimetallic NiCo nanoparticles were prepared by using inexpensive metal salts and sodium borohydride (NaBH4). The obtained Ni nanoparticles showed excellent catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol. The protocol creates a novel and facile route for the synthesis of metal nanoparticles.

Engineering the metathesis and oxidation-reduction reaction in solid state at room temperature for nanosynthesis

It is a long-standing goal to explore convenient synthesis methodology for functional materials. Recently, several multiple-step approaches have been designed for photocatalysts AgnX@Ag (X = Cl−, PO43−, etc.), mainly containing the ion-exchange (metathesis) reaction followed by photoreduction in solution. But they were obsessed by complicated process, the uncontrollability of composition and larger sizes of Ag particles. Here we show a general solid-state route for the synthesis of AgnX@Ag catalysts with hierarchical structures. Due to strong surface plasmon resonance of silver nanoparticles with broad shape and size, the AgnX@Ag showed high photocatalytic activity in visible region. Especially, the composition of AgnX@Ag composites could be accurately controlled by regulating the feed ratio of (NH2OH)2·H2SO4 to anions, by which the performance were easily optimized. Results demonstrate that the metathesis and oxidation-reduction reactions can be performed in solid state at room temperature for nanosynthesis, greatly reducing the time/energy consumption and pollution.

Green synthesis of BiOBr modified Bi2O2CO3 nanocomposites with enhanced visible-responsive photocatalytic properties

BiOBr/Bi2O2CO3 nanocomposites with mesh-like structures were simply synthesized by a green solid-state chemical reaction route with no extra template or surfactant. The as-synthesized nanocomposites have an altered thickness with the different composite ratio and exhibited excellent visible light photocatalytic activity for the degradation of dyes. The optimum photocatalytic activity of BiOBr/Bi2O2CO3 with a molar percentage of 60% was almost 25 times higher than Bi2O2CO3 towards degradation of RhB by visible-light. The enhanced photocatalytic activity could be attributed to the extended absorption in the visible light range and the formation of p–n heterojunctions between p-type BiOBr and n-type Bi2O2CO3 which promoted the photogenerated electron–hole separation. Radical scavenger experiments indicated that ·O2− and h+ played a major role during the RhB degradation process. The photocatalytic mechanism during the degradation process was also proposed.

Solvent-Free Chemical Approach to Synthesize Various Morphological Co3O4 for CO Oxidation

Co3O4 nanomaterials with diverse morphologies were usually synthesized in liquid phase accompanied by the template or surfactant under harsh conditions, which further restricted their practical application. Herein, we reported an extremely simple and practical solid-state chemical method to synthesize Co3O4-octahedrons, -plates, and -rods. Among these, the shape control of Co3O4-octahedrons and Co3O4-plates involve variation of the amount of reactant, and the formation of Co3O4-rods with {110} facet can be achieved by replacing the reactant. The formation of the Co3O4 nanomaterials with different morphologies originated from the different microenvironments of reaction and the structure of reactants. The catalytic activity of Co3O4 samples for CO oxidation was evaluated in normal feed gas. The as-prepared Co3O4-rods exposed {110} facet exhibited superior catalytic activity for CO oxidation, which can be attributed to more oxygen defects on Co3O4-rods surface. Additionally, Co3O4-rods exhibited excellent durablility (without pretreatment) in normal feed gas, even in the presence of moisture, comparable or better than that reported in the literature. The practical and environmental friendly solvent-free strategy provided a new promising route for large-scale preparation of (metal) oxide with remarkable CO oxidation performance for practical application.

Dahlia-shaped BiOClxI1−x structures prepared by a facile solid-state method: Evidence and mechanism of improved photocatalytic degradation of rhodamine B dye

A rapid and cheap solid-state chemical process was employed to synthesize BiOClxI1-x (x=1.0, 0.75, 0.5, 0.25, 0) solid solutions with dahlia-shaped hierarchitectures. The dahlia-shaped BiOClxI1-x hierarchitectures were effectively constructed by nanoplates with a thickness about 5-13nm. The band gap structure of the solid solutions can be modulated by adjusting the composition ratio of Cl and I, which has a significant effect on the photocatalytic activity of the solid solutions. The dahlia-shaped BiOClxI1-x (x=0.75) solid solution exhibits excellent adsorption and effective photocatalytic performances for rhodamine B (RhB) under visible light irradiation, which degraded more than 98% of RhB within 60min under the visible light irradiation, it is higher than the reported bismuth oxyhalides materials. The trapping experiments confirmed that O2- and h+ played the major role in the photocatalytic process and the possible photocatalytic reaction mechanism was illustrated.

Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures

The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS.

Green solid-state synthesis and photocatalytic hydrogen production activity of anatase TiO2 nanoplates with super heat-stability

A simple and environmentally friendly new method, a low-heating solid-state chemical method (LSCM), has been used to prepare uniform NH4TiOF3 nanoplates with a thickness of about 100 nm in the absence of surfactants. The solid–solid transformation was used to convert NH4TiOF3 nanoplates to TiO2 nanoplates with an exposed (001) facet via a simple sintering process at different temperatures. The anatase TiO2 nanoplates obtained in this work have super heat-stability, and can withstand high temperatures and maintain highly active anatase up to 1000 °C. The obtained compact TiO2 nanoplates have high photocurrent density and photocatalytic hydrogen-production activity, better than as-prepared TiO2 porous nanoplates and reported values in the literature, which is due to the exposed (001) facet and the high degree of crystallinity. This work provides a simple, efficient and environmentally friendly way to prepare TiO2 nanoplates and nanoparticles, and also offers a new approach for preparing anatase TiO2 with super heat-stability and high reactivity, which can be applied to H2-production via photocatalytic water splitting.