Preparation Of Molybdenum Oxide And Its Carbon Composites And Their Application In Supercapacitors

With the development of the global economy,the consumption of non-renewable resources on Earth accelerates day by day.Mankind is facing a situation of resource depletion and serious environmental pollution in the near future.Humans are seeking new economical,clean,efficient and environment-friendly energy sources and a new type of large-capacity energy storage device.As a new generation of energy storage devices,supercapacitors have the advantages of high power density,large capacity,long cycle life and high safety.They are widely concerned by people all over the world.The research of supercapacitor is the research of electrode materials.Searching for electrode materials with high energy density,high power density,low cost,and low environmental pollution has become a research focus for scientific researchers.The current research on supercapacitor electrode materials is mainly porous carbon materials,transition metal oxides,and conductive polymers.Carbon materials,low prices,good stability,but poor performance.Transition metal oxides have good electrochemical properties but poor stability.Conductive polymers are prone to poor expansion stability and low safety during charging and discharging.Although the transition metal oxides are poorly conductive,they provide higher energy density than carbon materials and are more stable than conductive polymers.Therefore,transition metal oxides are one of the hottest supercapacitor materials currently researched.As a layered transition metal oxide,molybdenum trioxide has a theoretical specific capacitance of 2700 Fg-1 and a large specific capacitance,which is of great promise for the application of molybdenum trioxide as a research supercapacitor material.So far,the specific capacitance of molybdenum trioxide reported is less than 50%of the theoretical value,so there is still much room for improvement in performance.How to improve the electrochemical performance of molybdenum trioxide as a supercapacitor material is also one of the hottest directions in the current study and deserves further study.The research in this paper is mainly based on the application of molybdenum trioxide and its carbon composites in supercapacitors.Specific work as follows:(1)Synthesis of molybdenum trioxide and its electrochemical properties.The molybdenum trioxide was synthesized in one step by a simple hydrothermal method and then annealed at a temperature of 500 ? for 12 hours to obtain the molybdenum trioxide active material having a stacked structure required for preparing a supercapacitor.After its chemical properties were studied,the specific capacitance was 1417 Fg-1,the energy density of the material was 126 Whkg-1,and the power density was 800 Wkg-1 when the current density was 2 Ag-1.However,the cycle stability is not good,When the current density is 10 Ag-1,the capacitance retention rate after cycling 2000 times is only 60%.(2)Synthesis of molybdenum trioxide and activated carbon composites and their electrochemical properties.Under the conditions of high temperature and high pressure,MoO3/C composite was synthesized by hydrometallurgy using ammonium molybdate tetrahydrate((NH4)6Mo7O24 · 4H2O)and 0.16 g activated carbon.The prepared composite has a layered structure with different sizes.The experimental results show that the specific capacitance of molybdenum trioxide and activated carbon composites can reach 251 Fg-1 at a current density of 1 Ag-1.When the current density is 5 Ag-1 and the window voltage is 1V,the capacity retention is 100%after 2000 cycles of charge-discharge.The energy density of molybdenum trioxide and activated carbon composites is up to 34.86 Whkg-1 and the power density is 500 Wkg-1.