Research On Structural Regulation And Energy Storage Performance Of Ruthenium Oxide Quantum Dots/reduced Graphene Oxide Composite

As one of the most promising candidates for the next generation of energy storage systems,supercapacitors have attracted extensive attention in recent years.How to improve the specific capacity,rate performance and cycling of electrode materials is still one of the challenges faced by supercapacitors.Ru O₂electrode material has a high theoretical specific capacitance,but the agglomeration of Ru O₂nanoparticles is easy to occur,and the active sites that react with the electrolyte are reduced.The specific capacitance of Ru O₂is reduced in the reaction process.Graphene,one of the carbon materials,has a large theoretical specific surface area and good electrical conductivity,which can be used as a carrier to compound with other materials.As a result,the ruthenium oxide nanoparticles and graphene for compound,can give full play to the synergy between them,have better electrochemical performance than the single material.In recent years,the experimental methods of preparing ruthenium oxide/graphene composites have been documented,which can be roughly divided into two types:sol-gel method and hydrothermal method.The particle size of ruthenium oxide composites prepared by these two methods is not uniform.Ruthenium oxide particles still agglomerate on the surface of graphene,resulting in the reduction of active sites and specific capacitance,and the preparation time is long.Therefore,how to effectively control the particle size,make it evenly dispersed on the surface of graphene and the preparation process to shorten the synthesis time and improve the synthesis rate of ruthenium oxide/graphene composites is the focus of research and has great practical significance.In this paper,the composite of ruthenium oxide quantum dots and reduced graphene oxide（GO）was designed and synthesized by microwave hydrothermal method,starting from Ruthenium chloride and GO.The specific research contents and results are as follows:（1）Preparation of reduced graphene oxide（r GO）,Ru O₂,Ru O₂QDs/r GO composites by efficient microwave hydrothermal method（preliminary preparation of the composites,at this time the mass mixing ratio of Ru O₂chloride and GO in the precursor solution was 1:4）.Firstly,the structure and electrochemical performance of r GO were studied by XRD,Raman,constant current charge-discharge test and cyclic performance test.The results show that the specific capacitance of r GO is 109 F/g at 1 A/g and 85 F/g at 10 A/g,and the rate performance is 77%.The decrease in the rate performance is due to the use of hydrophilic GO solution in the preparation of r GO.Therefore,the reduced r GO is more prone to stacking,and as an electrode material,its capacitance is lower than that of the electrode material at a high current density.In addition,the retention of specific capacitance of the electrode material decreases by 21%after 10000 cycles at 1 A/g current density,indicating poor cycling performance.Then Ru O₂was tested by TEM and BET,and the Ru O₂particles were agglomerated.The measured specific surface area was 149 m²/g.Finally,the structure of Ru O₂QDs/r GO was characterized by Raman,TEM and HRTEM tests.Compared with Ru O₂,the Ru O₂particles were uniformly dispersed in graphene sheet,and there was no obvious agglomeration phenomenon of the particles.The size of the particles was less than 10 nm by statistical measurement,belonging to Ru O₂quantum dots.BET test showed that the specific surface area of the composite was 365 m²/g,compared with that of pure ruthenium oxide（149 m²/g）.（2）Change the content of ruthenium chloride,systematically investigate the influence of the amount of ruthenium chloride on the morphology and electrochemical performance of ruthenium oxide particles in ruthenium oxide quantum dot/reduced graphene oxide composites,gradually increase the amount of ruthenium chloride,and find the best mass mixing ratio of ruthenium chloride and GO when the electrochemical performance is the best.The mass mixing ratio of ruthenium chloride and GO in different proportion precursor solutions was 1:2,and 1:1 and 2:1 were named RG-1,RG-2 and RG-3,respectively.The results showed that the size of ruthenium oxide particles increased with the increase of ruthenium chloride content.When mass ratio was 2:1,the particles began to agglomerate and dispersed unevenly in graphene sheets.When the ratio of mass was 1:1,the average particle size was 1.8 nm,and no agglomeration was generated on the graphene surface.The CV area of RG-2 prepared with mass ratio of 1:1 was the highest when the sweep speed was 10 m V/s,which indicated that RG-2 had the highest specific capacitance.RG-2 has a specific capacitance of 1120 F/g at a current density of 1 A/g.89%of the initial capacitance is retained after 10000 cycles.In conclusion,the optimal mass mixing ratio of ruthenium chloride and GO in the precursor solution is 1:1 by microwave hydrothermal method,which can prepare ruthenium oxide QDs/r GO electrode materials with excellent electrochemical performance.