Study Of The Performance Of Graphene Hydrogel Electrodes Based Supercapacitors

Graphene has extensive application prospect in various aspects like supercapacitors electrodes, sensors, drag carriers because of its light quality, large surface area and good conductivity.In this thesis, we prepared3D graphene hydrogel network by in situ method with graphene oxide as precursor and used it as electrodes. We controlled the mass density, conductivity, and pore structure by changing the reaction conditions, tested their electrochemical properties, and found the best conditions in preparing the graphene hydrogel for supercapacitors.The main contents are as follows.(1)We have investigated the effects of electrode mass density on electrochemical properties of supercapacitors by using the graphene oxide dispersion with different concentration as precursors. The experiments showed that the supercapacitors with graphene hydrogel electrodes have superior performance than that with graphene powder electrodes.(2)We have explored the severe conditions forming the graphene hydrogel when sodium sulfide solution was used as the reductant and the mass ratio between graphene oxide and sodium sulfide ranged from10:1to1:10. When the ratio is2:1, the graphene hydrogel has a conductivity of1S/m, and the supercapacitor based on which has a specific capacitance of187F/g.(3)We have investigated the effects of the low-temperature reduction stage on electrochemical properties of graphene hydrogel. A longer stage shows a bigger pore size. The specific capacitance of supercapacitorsbased on these electrodes ranges from130F/g to184F/g at the current density of2A/g.(4) We have investigated the effects of electrolytes on the performance of graphene hydrogel based supercapacitors. Solutions of Na2SO4, NaCl, KCl and KOH were used as electrodes. The supercapacitorswithNaCl solutionelectrolyte have the best electrochemical properties.(5)We have investigated the effects of current collectors on the performance of graphene hydrogel based supercapacitors. Thesupercapacitors with nickel foam have a more symmetrical CV curves but those with copper foil had a higher specific capacitance.In this thesis, there are52figures,6tables and64references.