Preparation And Supercapacitive Properties Of Graphene/Rare Earth Oxides (Hydroxide)

While the social economy is steadily moving towards high-quality development,the construction of ecological civilization cannot be ignored.Traditional chemical power sources can no longer meet the urgent needs of the national strategy for new energy sources,so the requirements for energy storage devices are becoming more and more stringent.Supercapacitors have a series of advantages such as high current and rapid charge and discharge,excellent cycle stability and high power density.Rare earth metal oxides（hydroxide）have become one of the hottest materials in the field of electrochemistry such as supercapacitors due to their special nanostructures and pseudocapacitive properties.As soon as graphene came out,it attracted numerous scholars to discuss it.It has good electrical conductivity and can be combined with different materials in a variety of ways between the two-dimensional structure sheets.In this paper,rare earth oxides（hydroxide）and graphene composites are used to prepare supercapacitor electrode materials to improve their overall performance.Self-supporting 3D Reduced graphene oxide（rGO）/CeO₂ composites were prepared by a simple one-step hydrothermal synthesis method.Self-supporting materials with better performance can be obtained by adjusting different ratios of reducing agent and morphology control agent.The XRD test shows that CeO₂ has been successfully prepared and compounded on the rGO sheet,and some interactions have been generated.The pore size distribution is mostly mesoporous,and the specific surface area is 150.5 m²·g^-1.SEM,TEM,XPS,etc.showed that the composite results were good.The electrochemical performance of the three-electrode system is good,and the specific capacitance of Self-supporting 3D rGO/CeO₂ is as high as 451 F·g^-1 at a current density of 0.5 A·g^-1.After 10,000 charge-discharge cycles,the Self-supporting 3D rGO/CeO₂ capacitance retention rate was as high as 95.9%.The energy density of the assembled rGO/CeO₂||rGO is as high as 39.08 Wh·kg^-1at the power density of 120 W·kg^-1,and the capacitance retention can still reach 88.9%.rGO/CeO₂ composites were obtained by a simple microwave-assisted synthesis method.By morphology observation,CeO₂ is uniformly distributed on the wrinkled rGO in the form of particles.The specific surface area is as high as 206.7 m²·g^-1,and the pore size is mesoporous distribution.Through electrochemical tests,the specific capacitance of rGO/CeO₂ is as high as 468 F·g^-1(measured at a current density of 0.5 A·g^-1),and the capacitance retention rate is as high as 107.3%after 10,000 charge-discharge cycles.Assembling rGO/CeO₂ into a symmetric supercapacitor rGO/CeO₂||rGO/CeO₂ obtained a power density of 100 W·kg^-1,and the corresponding energy density was 18.16 Wh·kg^-1.rGO/La（OH）₃ composites were also successfully prepared by a simple microwave-assisted synthesis method.Its specific surface area is 85.8 m²·g^-1.At a current density of 0.5A·g^-1,the specific capacitance of rGO/La（OH）₃ in the three-electrode system is as high as757 F·g^-1,and the capacitance retention rate is still 97.7%after 10,000 charge-discharge cycles.The capacitance retention rate of the symmetric supercapacitor rGO/La（OH）₃||rGO/La（OH）₃ is as high as 96.8%,and the maximum energy density is 24.09Wh·kg^-1 when the power density is 275 W·kg^-1.The assembled asymmetric supercapacitor rGO/La（OH）₃||rGO has a capacitance retention rate of 91.3%and a maximum energy density of 55.65 Wh·kg^-1 at a power density of 275 W·kg^-1.They are all at the mainstream level of water-based electrolyte supercapacitors.