Polyoxometalates-based Graphene Composites:Synthesis And Electrochemical Performance Application

With the rapid consumption of fossil energy and the corresponding global warming problem,the development of advanced energy storage technology has attracted wide attention of scientists.Supercapacitors are considered to be one of the clean and renewable energy storage devices.Graphene has attracted many researchers with excellent performances,improving the rapid transfer of electron charge and the specific capacitance of electrode materials.In recent years,the wider application of solid supercapacitors has become a research hotspot in the energy field due to its higher energy density and power density.?1?Graphene was used as the base material,and a new composite electrode material was prepared by one-step hydrothermal method with Co-POM,of which has high electrical conductivity and high specific surface area.Material reducing graphene oxide has great performance that the specific capacitance can even reach156.2 F g^-1 at a current density of 0.5 A g^-1.?2?Co-POM composites were successfully prepared by one-step hydrothermal method.Graphene was used as the base material,Co-POM was supported on the graphene sheets,and the high specific surface area and high electrical conductivity of graphene were combined.The reversible redox capability of Co-POM material increases the specific capacitance of the supercapacitor electrode material.At a current density of 0.5 A g^-1,the capacitance of Co-POM/rGO reaches 211.3 F g^-1,and the specific capacitance of Co-POM/rGO increases by 35.3%.?3?Single-atom-metal doped hybrid?Co-POM/rGO?was synthesized successfully by directly deposition of Co-polyoxometalate on the surface of reduced graphene aerogel via one-pot hydrothermal treatment.As electrode materials of supercapacitors,Co-POM/rGO showed high-performance electrochemical energy storage(211.3 F g^-1 at 0.5 A g^-1).Furthermore,the solid-state asymmetric supercapacitor?ASC?device,using Co-POM/rGO as a positive electrode,exhibited an outstanding energy density of 37.6 Wh kg^-1 at a power density of 500 W kg^-1,and high capacitance retention of 95.2%after 5000 charge-discharge cycles.