Research Of Nitrogen-doped Graphene Hydrogel In Aqueous Supercapacitor

Graphene hydrogel has recently been focus of many studies because of its high specific surface area, low density, nano-micropore structure, multidimensional electron transport pathways, good electrical conductivity and good thermal stability. Therefore, graphene hydrogel has important and potential applications in the field of super capacitor. Nitrogen doping is an important means developed in recent years to produce graphene hydrogel with high capacitance. It was found to be an effective method to alter the properties of graphene hydrogel since nitrogen chemically blinds to the carbon lattice of graphene hydrogel. Morever, nitrogen has a comparable atom size and high eletronegativity compared to carbon. Although some methods have recently been reported to synthesize nitrogen-doped graphene hydrogel, such as CVD method, arc discharge method and so on. Compared with those methods, the low-temperature method reported in this work has a merit of mild conditions. Therefore, this thesis has mainly done the following research:(1) Na2S and Ascorbic acid had been used to prepare graphene hydrogel that have been analyzed with XRD, SEM and Laman. It has been proved that graphene hydrogel using Na2S as the reducing agent have a specific capacitance and cycle performance, thus draws the conclusion:alkaline reducing agent is suitable for preparation of graphene hydrogels.(2) KOH, H2SO4and Na2SO3solution had been used as electrolyte. The electrochemical performance of graphene hydrogel using KOH have a specific capacitance and cycle performance.(3) A new nitrogen doped method had been used to prepare nitrogen doped graphene hydrogel that have been analyzed with XRD, SEM and XPS. A comprehensive comparison had been made between graphene hydrogel and nitrogen doped graphene hydrogel. It has been proved that nitrogen doped graphene hydrogel have a specific capacitance and cycle performance.(4) To explore the optimal doping ratio of the new nitrogen doped method. In the doping process, the graphene oxide solution and nitrogen source were placed together with the weight ratio of8:1,6:1,4:1and2:1.The electrochemical performance tests were conducted to explore the optimal doping ratio. The results show that the strongest performance of nitrogen doped graphene hydrogels were prepared by the ratio of4:1, which have a specific capacitance and cycle performance. (5) To explore the optimal doping time of the new nitrogen doped method. In the doping process, the nitrogen doped graphene hydrogels were doped in5hours,10hours and15hours. The electrochemical performance tests were conducted to explore the optimal doping time. The results show that the nitrogen doped graphene hydrogels,which were doped in10hours, have the best specific capacitance and specific performance.