Controlled Synthesis And Property Studies Of Iron Oxide-Based Heterostructures

In recent years,the study of two-dimensional nanomaterials with unique physical and chemical properties has attracted wide attention.As an important function material,two-dimensional iron oxide nanomaterials with high specific surface area show broad application potentials in the field of magnetic,lithium-ion batteries,photocatalysis and so on.Hematite(α-Fe2O3)is an n-type semiconductor material with a relatively narrow band gap energy(2.2 eV)well corresponding to the visible spectrum.Unfortunately,its promising application in photocatalysis is hampered by poor charge carrier mobility,short hole diffusion length,and high electron-hole pair recombination rate.Coupling Fe2O3 with other semiconductors has been considered as an alternative strategy for achieving good performances in photocatalysis,but also in other fields,such as lithium-ion batteries and ultracapacitors.In this paper,a series of novel iron oxide-based nanostructures were designed and synthesized.These heterostructures have shown remarkable enhancements in photocatalytic performances and lithium storage properties.The main contents of this thesis are sumarried as follows:(1)Controlled Synthesis of α-Fe2O3/SnO2 Heterostructures with Improved Lithium-Ion Battery PerformancesWe reported the synthesis of a novel gear-like 2D-1D α-Fe2O3/SnO2 hetero-structures composed of SnO2 nanorods and α-Fe2O3 nanoplates by a facile hydro-thermal method.α-Fe2O3/SnO2 sandwich like 2D-1D heterostructures were obtained by adjusting the reaction time.Moreover,the electrochemical properties of α-Fe2O3/SnO2 sandwich like heterostructures as an anode material for lithium-ion bat-tery were tested.The material shows excellent lithium storage properties compared withα-Fe2O3 nanoplates and SnO2 nanorods.The heterostructures show higher capacitiy(308 mAh/g)retention compared to the pristine SnO2 nanorods(148 mAh/g)and α-Fe2O3 nanoplates(158 mAh/g)after 30 cycles at a current densities of 100 mA/g.The synthesis strategy can be easily extended to the growth of other tin-based composite oxide(e.g.Zn2SnO4)as secondary nanorods on the primary α-Fe22O3,forming the hierarchical nanostructures including α-Fe2O3/Zn2SnO4 2D-1D heterostructures andα-Fe2O3/SnO2 3D-1D heterostructures(2)Synthesis of γ-Fe2O3@MoS2 Core-Shell 2D-2D Heterostructures with Improved Lithium-Ion Battery Performance and Photocatalytic Propertyα-Fe2O3@MoS2 core-shell 2D-2D heterostructures are synthetised by a facile hydrothermal method and subsequent calcination.Firstly,a novel α-Fe2O3@MoS2 core-shell 2D-2D nanocomposite was fabricated by depositing MoS2 nanosheets on the surface of α-Fe2O3 nanosheets with the assistance of glucose.Then,a γ-Fe2O3@MoS22D-2D nanocomposite was obtained by subsequent calcination of the α-Fe2O3@MoS2 nanocomposite under nitrogen atmosphere.The γ-Fe2O3@MoS2 2D-2D nanocomposite was applied in photocatalytic degradation of methylene blue dye and lithium ion bat-tery,and both showed significant enhanced performances.For photochemical catalysis of Methylene Blue with the excitation of UV-visible light,the corresponding degra-dation rate of the γ-Fe2O3@MoS2 nanocomposite was 95.9%after three hours,while the degradation rates of the γ-Fe2O3 nanosheets and MoS2 nanosheets were only 76.6%and 76.5%.Moreover,as a lithium ion battery anode material,γ-Fe2O3@MoS2 core-shell structure showed a high reversible discharge capacity and rate performance compared with γ-Fe2O3 nanosheets and MoS2 nanosheets.The γ-Fe2O3@MoS2 core-shell heterostructures show higher capacities(308 mAh/g)retention compared to the pristine γ-Fe2O3 nanosheets(202 mAh/g)and MoS2 nanosheets(134 mAh/g)after 220 cycles at a current densities of 100 mA/g.(3)Synthesis and Properties of α-Fe2O3@TiO2 Sandwich NanostructuresIn order to improve the photocatalytic performance and lithium battery performance of iron oxide,novel α-Fe2O3@TiO2 sandwich-like nanomaterials were prepared.Firstly,novel α-Fe2O3@TiO2 sandwich-like nanomaterials were fabricated by depositing TiO2 on the surface of α-Fe2O3 nanosheets with the assistance of ultrasonic.Then,the α-Fe2O3@TiO2 core-shell heterostructures were applied in photocatalytic degradation of Rhodamine B dye and lithium ion battery,and both showed significant enhanced performance.Moreover,two-dimensional anatase TiO2 hollow nanoplates were synthesized by etching of α-Fe2O3 nanosheets in hydrochloric acid.The photocatalytic performance of TiO2 was investigated by decomposing rhodamine B under simulated sunlight.Among the TiO2 samples,the anatase TiO2 hollow nanoplates synthetized at 350℃ manifested a significant enhancement in the photocatalytic performances.(4)Synthesis of Sn/C Microsphere Composites with Improved Lithium-Ion Battery Performance by Vapour-Liquid-Solid Reaction(VLS)Using carbon coated ZnSnO3 nanospheres as precursor materials,The Sn/C microsphere composite was synthesized by Vapour-Liquid-Solid Reaction(VLS),and the composite was investigated as anode material of lithium-ion battery.At a current density of 100 mA/g,the discharge capacity was maintained at 394 mAh/g after 200 cycles,exceeding the theoretical specific capacity(372 mAh/g)of graphite.This method does not only enable us to synthesizes a high capacity lithium battery anode material but also provides us a way to explore the VLS reaction by optimizing the reaction materials.