Crystalline Mesoporous Metal Oxides:Synthesis And Electrochemical Properties

Since the first successful synthesis of M41s type mesoporous materials reported by the scientists of Mobil,mesoporous materials,as a new member of porous materials,have attracted great attention.The emerged mesoporous materials possess highly ordered structure,uniform pore diameter,large surface area,open accessed pores and etc.All the features make it potential to find wide applications in catalysis,adsorption,sensors and so on.Mesoporous metal oxides possess both nano-properties of materials and porous structures,which make it potential to have applications in catalysis,optics,electrics,magnetics and so on.The general synthetic methods of mesoporous metal oxides are soft-templating and hard-templating method.People can prepare mesoporous metal oxides with the crystallized wall structures and the ordered mesoporous structures by hard-templating method.However,the method is complicated and expensive,which make it just suitable for the synthesis of a small amount targets in labs.Conversely,the soft-templating method can be used for the large scale preparation.But the products only have amorphous or semi-crystalline frameworks,which lead to poor thermal and mechanical stability,restrict the range of applications of the materials.Therefore,synthesis of mesoporous metal oxides with crystalline frameworks becomes the vital topic of the area.In this thesis,we focused on the defect of the soft-templating method and tried to modify the soft-templating route,which could be used for the synthesis of crystalline mesoporous Fe2O3 and NiCo2O4.At last,the prepared materials were applied as an anode material for lithium-ion batteries.The major research contents of the thesis were summarized as follows:1.Crystalline mesoporous ?-Fe2O3:solvent-free synthesis,characterization and electrochemical performanceWe developed a solvent-free route with a soft template for synthesizing mesoporous ?-Fe2O3.The solid raw materials of Fe(NO3)3·9H2O and the triblock copolymer F127 were mixed together and melted at 80 ?.The crystalline mesoporous?-Fe2O3 was obtained by three-step calcination(Ar,H2O(g)and Air).The specific surface area of the product was as high as 146 m2/g and the average pore diameter was 3.1 nm.While applied as an anode material for lithium-ion batteries,it showed a high reversible capacity(1120 mAh/g),excellent cycle performance(a discharge capacity retention of 86.0%for over 150 cycles)and rate performance.2.Crystalline mesoporous ?-Fe2O3:aqueous solution synthesis,characterization and electrochemical performanceWe proposed an aqueous solution route with a soft template for synthesizing mesoporous ?-Fe2O3.In this work we started with mixed Fe(NO3)3·9H2O and F127 solution.With the same post-processing,we got the crystalline mesoporous ?-Fe2O3 with high surface area(131 m2/g)and uniform pore size(4.0 nm).Compared to the products of the solvent-free synthesis,the products of the aqueous solution synthesis exhibited higher crystallinity but a little worse electrochemical performance.3.Crystalline mesoporous NiCo2O4:aqueous solution synthesis,characterization and electrochemical performanceOn the basis of the aqueous solution route we started with mixed Ni(NO3)2·6H2O,Co(NO3)2·6H2O and a soft template solution.With the argon and air treatment we got the crystalline mesoporous NiCo2O4 with high surface area(147 m2/g)and uniform pore size(3.9 nm).As an anode material for lithium-ion batteries,it showed high capacity(770 mAh/g)and good cycle performance(a discharge capacity retention of 84.2%for over 300 cycles).