The Regulation Of Oxygen Vacancies In Transition Metal Oxides And Their Capacitance Properties

Among the many factors affecting the supercapacitor,the electrode material plays a decisive role in its overall performance.Oxygen vacancies can regulate the structure of the electron band,increase layer spacing,and establish highly active REDOX sites.At the same time,oxygen vacancy can also promote the rapid transfer of charge.Based on this,the oxygen vacancies of transition metal oxides were regulated by redox co-precipitation and hydrothermal methods.The crystal structure,morphology and growth mechanism were analyzed by SEM,TEM,XRD,XPS,EPR and other characterization techniques.The capacitance performance was studied by electrochemical technology.The detailed study is as follows:1.Europium-doped Mn O2(Eu5%-Mn O2)ultra-thin nanosheets(3.4 nm)with rich oxygen vacancy have been synthesized by a simple REDOX coprecipitate method.The results of XPS and EPR show that the ratio of Mn3+/Mn4+ and the oxygen vacancy increases after Eu doping.The specific capacitance of Eu5%-Mn O2 at 1 A g-1 is 361.2 F g-1 and remains 100% after 10000 cycles at 10 A g-1.The assembled Eu5%-Mn O2//AC ASC device at 1 A g-1 can reach 63.36 F g-1 and exerts 19.8 Wh kg-1 of energy density when the power density is 373.2 W kg-1.2.Using V2O5 aerogel as a strong oxidant and acid catalyst,3,4-ethylenedioxythiophene(EDOT)monomer was oxidized and polymerized on V2O5 ultrathin nanosheets to form PEDOT/V2O5 ultrathin nanosheets with a thickness of about 4.4 nm.AFM results show that the thickness of poly(3,4-ethylenedioxythiophene)(PEDOT)on V2O5 nanosheets is approximately0.9 nm.The results of XPS and EPR confirm that the polymerization of PEDOT induces more oxygen vacancies in V2O5.In addition,the specific capacitance is406 F g-1 at 2 m V s-1 and capacitance retention rate is 95% after 5000 cycles,respecitively.The energy density of ASC composed of PEDOT/V2O5 anode and activated carbon cathode reaches 65 Wh kg-1 at a power density of 1490.4 W kg-1.3.PEDOT/Mo O3 was prepared by the polymerization of EDOT on the surface of prepared Mo O3 nanobelt using Fe Cl3 as oxidant.XPS confirmed that thepolymerization of PEDOT on the surface of MoO3 can induced oxygen vacancy.The specific capacitance of PEDOT/Mo O3 at 5 A g-1 in 1 M H2SO4 electrolyte is857 F g-1;remains 95% after 5000 cycles,showing good stability.