| Metal chalcogen compounds are an important branch of nanomaterials, and a variety of metal chalcogen nanomaterials have been prepared by scientists recently. They have numerous types and possess special optical, electrical, magnetic and mechanical performance, as well as many valence states and valence electron configurations, therefore, have been widely used in the fields of catalysis, sensor, photovoltaic, batteries, medical and other fields. One-dimensional (ID) nanomaterials could be used as design units of nano- and micro devices due to their special geometric morphology and two dimensional quantum size effect, as well as directly electron transfer properties. In addition, researchers could use them to join nanodevices, and investigate their electron transport and optical properties related to dimension. Hence, the structural design synthesis and performance improvement study of 1D metal chalcogen nanomaterials are of important research significance.In this thesis, after choosing proper reaction system and optimizing the reaction conditions constantly, one dimensional nanostructures and three dimensional self-assembled metal chalcogen nanoarchitectures based on 1D nanostructures with high crystallinity and uniform size/morphology have been synthesized by using hydrothermal and thermal deposition methods. Relative performance studies based on the as-prepared samples have been developed, such as degradation of dye wastewater under visible light, electrochemical supercapacitor characterization, PL properties, water splitting, and humidity sensing properties, and aim to improve their performance through designing the nanomaterials’structure, morphology and composition. The main points of this thesis are summarized as follows:(1) Ultralong cannonite Bi2O(OH)2SO4 nanobelts with widths of 30-50 nm and thicknesses of about 10 nm, and lengths up to millimeter have been successfully fabricated through hydrothermal method with SDS as surfactant. These single crystalline nanobelts were self-assembled in the form of macroscopic architecture floating in the solution which could be transferred onto many other substrates on a large scale (> 1.5 cm×1.5 cm in area and about 3 μm in thickness). The growth process and influence of reaction conditions on the morphology and components of the products have been investigated carefully, as well as photocatalytic degradation ability to several dye effluents under visible light irradiation. The dark adsorption and photocatalytic process of dyes can be better described by the pseudo-second-order model than the pseudo-first-order model. The results indicate that the nanobelt film possesses excellent photocatalytic performance to MB, RhB, MO and Congo red, implying it has good application prospect in the future.(2) Cannonite Bi2O(OH)2SO4 microrods with diameters of 1-4μm and lengths up to hundreds of micrometer have been successfully fabricated through hydrothermal method with SDS as surfactant at a lower reaction temperature. The microrods could be used as supercapacitor electrode material, and the electrochemical characterizations such as cyclic voltammetry, charge-discharge and cycling performance of microrods and nanobelts prepared in the previous chapter have been investigated in 6 M KOH electrolyte. The results indicate that the specific capacitance of microrods could achieve 986.3 F g-1 when the current density is 0.5 A g-1, and microrods possess a higher capacitance, better rate specific capacitance retention and cycling performance. Here, we successfully explore the potential application of our cannonite Bi2O(OH)2SO4 in the field of electrochemical supercapacitor.(3) Bowknot bundle shape nanostructure precursor composed of Bi2O2CO3 and Bi2O3 with lengths range from 25-30 μm have been successfully fabricated through hydrothermal method with PVP as structure-directing agent. This bowknot bundle shape nanostructure precursor is actually composed of feather-like nanostructures. The widths of the feather are 200-350 nm, and the middle of the feather is solid with diameters about 60 nm. And then Bi2S3 nanotube bundle with diameters about 50-60 nm have been synthesized by using the precursor as hard template, which reacted with sulfur ions and then through an "inward chemical etching method" to remove the unreacted precursor. The influences of additive on the morphology and growth process of precursor have been investigated, as well as the PL properties. The results indicate that the PL emission is located at 450-470 nm, and the emission intensity is highly related with its morphology.(4) WO3 nanorod array film with diameters of 30-100 nm and lengths about 1 μm have been prepared on Si wafer by thermal evaporation in a vacuum furnace. The growth mechanism of WO3 nanorod fits vapor-solid process. Furthermore, humidity sensing device has been directly fabricated based on the nanorod array and tested at room temperature. The results indicate that the PL type humidity sensor exhibits high sensitivity, quick response-recovery, repeatability, and good linearity. The good properties are ascribed to the existing proper amount of oxygen vacancies in the nanostructure.(5) Furthermore, WO3 nanorod nanoforest has been prepared on our self-modified Si micropillar (diameters around 2μm, approximately 7.5 μm tall, and a regular pitch of about 5 μm) arrays by thermal evaporation mehtod. Photoelectrochemical electrode has been fabricated based on WO3 nanorod nanoforest and planar WO3 nanorod array film, and their water splitting performance is tested in neutral electrolyte. The results show that nanoforest configuration generates higher photocurrent (ca.0.60 mA cm2-) compared with planar nanorod film (ca.0.37 mA cm2-) at 1.23 V vs. RHE, due to its higher surface area and shorter electron transport lengths. Moreover, the existing oxygen vacancies in the nanostructure played a pivotal role of its good photostability in neutral electrolyte. |
PDF Full Text Request