The Preparation And Electrochemical Properties Of Graphene Composite Microsphere

The graphene has been widely used in the field of electrochemistry due to its single-atom thickness, high surface area, and exceptional physical and chemical properties. However, graphene sheets tend to form irreversible agglomerates, causing the performance cannot be fully utilized. The purpose of this experiment was to design out-of-plane space by bringing in "spacers" between graphene sheets and prepare the graphene composite microsphere with high surface area used in supercapacitor and electrosorption.The graphene/composite microsphere (GCM) was synthesised by a simple-inverse suspension polymerisation under ambient pressure drying and carbonisation in a nitrogen atmosphere. The GO reacted with RF at the interface formed by water and hexamethylene under high speed stirring, and the temperature was 60℃. The results showed that the diameters of the graphene oxide/resorcinol-formaldehyde microsphere (GORFM) were controlled in the range of 5-10 μm with perfect sphericity. The inner layer of GORFM was composed of resorcinol-formaldehyde (RF) particles, and the outer layer was the wrinkled GO sheets intercalated with RF through chemical and physical interactions. The spherical structure was propped up mainly depend the chemical bonding between GO and RF. The GCM-1.5 sample was mesopores and achieved the highest specific surface area of 1128 m2/g and the mesopores area of 699 m2/g.The GCM was applied to the supercapacitor as electrode material, having approximate rectangle structure of cyclic voltammogram curves. The constant current charge and discharge curves for GCM were typical triangular shape and perfectry symmetrical in charging/discharging process, indicating that the GCM as electrode materials with ideal electric double-layer capacitor behavior. The GCM-1.5 had the minimum interfacial charge transfer resistance and the maximum specific capacitance of 290.2 F/g and the specific capacitance of GCM-1.5 could keep a 98.3% after constant charge-discharge process for 1000 times, indicated that the GCM-1.5 has a good circulation stability and better rate performance. Which was belonging to the GCM-1.5 had an excellent porous structure, high surface area, so that the ions could diffuse and transfer rapidly in the pore channel.The GCM-1.5 was applied to the electrosorption as electrode material. The adsorption capacity was up to 27.76 mg/g at the voltage of 1.6 V, and the charge efficiency was 77.8-81.4%, which was about twice of activated carbon. The adsorption capacity of GCM-1.5 was increased from 20.76 mg/g to 33.52 mg/g with the voltage increased from 1.2 V to 1.8 V, According to the study on the adsorption behavior of different valence of ion indicated that the electrode materials had a strong selective adsorption of potassium ions, which was decided by the internal pore structure of electrode materials, meanwhile, the smaller hydrated radius of the ions in solution, more ion valence and weaker bonding strength between ions and water, leading to the higher adsorption capacity.