| Metal oxide nanostructure materials, which have excellent physical and chemicalproperties due to the shape anisotropy, have attracted worldwide attention. Iron oxidenanomaterials (Fe2O3and Fe3O4) have been researched extensively in many fields,such as gas sensors, lithium-ion batteries, catalysis, and waste-water treatment,because of its inexpensive, non-toxic, chemical stability and other perfect physical andchemical performance. However, so far few publications reported the application of3-D iron oxide nanomaterials in gas sensor and lithium-ion battery. protection．Thedevelopment of gas sensor and lithium-ion battery and iron oxide materials arereviewed in details. In this thesis,3-D Fe2O3and Fe3O4/C nanomaterials were preparedby simple solution-based reaction and hydrothermal method, respectively. Themicrostructure and physicochemical properties of the as-synthesized Fe-based Metaloxide nanomaterials were characterized by X-my diffraction(XRD)，scanning electronmicroscopy(SEM), transmission electron microscopy(TEM), BET analysis, andthermogravimetric analysis (TGA). Furthermore, the gas sensor and lithium-ion batteryperformances of the as-synthesized iron oxide nanomaterials were also studied. Thedetails are summarized as follows.In chapter2, mesoporous flowerlike and urchinlike α-Fe2O3has been successfullysynthesized by a simple solution-based reaction, and sequentially calcination. Detailedexperiments demonstrated that the morphology of the hierarchical α-FeOOHprecursors could be easily controlled by adjusting the experimental conditionsincluding reactant concentration, solvent composition, reaction time and reactiontemperature. On the basis of time-dependent experiments, a multistage growthmechanism for the formation of the α-FeOOH super-architectures was proposed. Thismethod is expected to be a useful technique for controlling the diverse morphologies ofiron oxide superstructures. In addition, due to their unique hierarchical mesoporousstructure and comparative high specific surface areas, these obtained α-Fe2O3nanostructures could meet the demands of a variety of applications, such as gas sensors,lithium-ion batteries, catalysis, waste-water treatment, and pigments.In chapter3, porous urchin-like α-Fe2O3nanostructures with n-typesemiconducting properties were prepared by a simple solution route and sequentiallycalcinations. The as-prepared sensor showed good H2S sensing performances with short response/recovery time within10s, and relatively low detection limit of1ppm.Interestingly, it was observed abnormal n–p transition sensing behavior induced by thevariation of working temperature and p-n transition sensing behavior related to theincreases of H2S concentration. Large density of unstable surface states resulting fromhigh surface-to-volume ratio would be beneficial for the formation of a surfaceinversion layer and accounted for the n–p transition. These results help us tounderstand the sensing mechanism of α-Fe2O3and hint the potential application of theas-prepared sensor in monitoring H2S.In chapter4, carbon-coated urchin-like Fe3O4composite has been successfullysynthesized using inexpensive starting materials. The urchin-shapednano/miro-structure was consisted of several oriented nanorods with an averagediameter of30-40nm. TEM analysis revealed that there is a large number of pores anduniform amorphous carbon distribution at a nanoscale in the nanorods walls. As usedin lithium-ion batteries, the mesoporous Fe3O4/C anode delivered a higher reversiblecapacity of about830mAh g-1at0.1C up to50cycles, as well as enhanced high-ratecapability compared with urchin-like Fe2O3and commercial Fe3O4. The improvementscan be attributed to the combined effects of the nano/micro-architecture, the porosity,and the ultra-fine carbon matrix, where the three factors would contribute to possessboth the merits of nanometer-sized building blocks and micro-sized assemblies, andprovide high electronic conductivity. |
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