Preparation Of Nanostructured Transition Metal Oxides And Their Applications In Energy Storage And Conversion

As traditional fossil fuels,such as coal,oil and natural gas,have become increasingly exhausted and industrialized,the pollution of water is becoming more and more serious.The search for new energy?such as solar energy,wind energy,geothermal energy,tidal energy,etc.?has become a hot spot of research.However,as clean energy,solar energy,wind energy,geothermal energy and tidal energy are mostly intermittent.With the rapid progress of society and the rapid development of science and technology,the productive forces are advancing rapidly and the people's demand for energy has increased rapidly.Clean energy such as solar energy and wind energy can hardly deal with the contradiction between the current energy demand and the environmental pollution.The research on new energy storage facilities and new materials for improving environmental pollution has become impatient.As green and efficient energy storage equipments,supercapacitors?also called electrochemical capacitors?and lithium ion batteries have great application value in the fields of daily electronic products,storage and backup systems,electric vehicles,power systems and aerospace and other fields.In this paper,Ni@MnO₂ and Fe₂O₃/GO nanocomposites were obtained by new synthesis methods.With the introduction of nickel,Ni@MnO₂ can enhance electrical conductivity and improve the role of manganese oxide as a catalyst for catalytic 4-NP.It can be applied to the cathode materials of supercapacitor and degradation of 4-NP.Because of the introduction of GO,the conductivity of Fe₂O₃/GO is improved and the the problems of agglomeration and expansion collapse could be solved.And it can be applied to the anode materials of lithium ion batteries1.Manganese oxide has received great attention because of its abundant,non-toxic,pollution-free,easy to synthesize and multifunctional applications.Compared to the general manganese oxide,multilevel layered manganese oxide nanostructures are considered to be beneficial to make full use of itself because of exposing more surface area and active sites.Besides,the introduction of other materials that overcome the shortcomings of manganese oxide can enhance the performance of materials.Under hydrothermal conditions,the Ni@MnO₂nanostructure coated alternately with a thickness of only 10 nm MnO₂ outside Ni nanowires were obtained through the reduction reaction with KMnO₄ on the surface of nickel nanowires.Because of the good electronic and ionic conductivity of nickel nanowires,Ni@MnO₂ nanocomposites exhibit good electrochemical properties.As a supercapacitor positive material,at the current density of 1 A g^-11 in 1 M Na₂SO₄solution,the discharge specific capacity is up to 263.1 Fg^-1,after 5000 cycles,the capacity under the current density of 5 A g^-11 almost does not decrease.When the asymmetric capacitor was formed with activated carbon material,the two electrode tests were carried out under 1 M Na₂SO₄ solution,and the potential window could reach up to 2 V.When the power density is 500 W kg^-1,the energy density reaches41.5 Wh kg^-1,and when the power density is 5000 W kg^-1,the energy density reaches13 Wh kg^-1.During the long cycle test,at the current density of 5 A g^-11 for 2000 times,the specific capacitance retention rate can reach 83%.In catalytic degradation,0.12mM 4-NP solution can be completely degraded in 12 minutes and the rate constant?k?reached 0.169.2.Graphene oxide?GO?loaded iron oxide nanomaterials have been widely studied as anode materials for lithium ion batteries.On the basis of the introduction of KMnO₄ and nickel foam,for the first time,we prepared Fe₂O₃/GO with 10 nm iron oxide nanorods loaded into graphene oxide by one pot method at 80 ^oC after adding FeCl₃�6H₂O and graphene oxide based on mixing KMnO₄ and Ni.The experiment was easy to operate and greatly reduced the experimental step.Because of the introduction of graphene oxide,the electronic and ionic conductivity of Fe₂O₃/GO are greatly enhanced,and the agglomeration and expansion collapse of iron oxide nanoparticles can be overcome because of the good mechanical properties of graphene oxide.At the same time,because of its smaller nano size the Fe₂O₃ nanorods loaded on GO shorten the transmission distance of lithium ions and electrons.As a cathode material for lithium ion batteries,Fe₂O₃/GO shows high specific capacity and cyclic stability,and the reversible specific capacity is 1001 mAh g^-11 after 500 times at 200mA g^-1.(711 mAh g^-1based on the total mass of Fe₂O₃/GO).