Preparation Of MnO₂/Graphene Composite Films And Their Application To Supercapacitor Electrodes

Supercapacitor is regarded as an efficient and environmental friendly energy storage andsupply technology for its high power density and low pollution. To explor new materials with lowcost, high performance, environmental benignity is important to promote the commercialization ofsupercapacitors. Carbon materials are the widely used electrods due to their low cost and goodelectrical conductivity. Thereinto graphene is the ideal electrode materials because of its goodelectrical conductivity, thermodynamic performances and mechanical properties, as well as hugespecific surface area (The theoretical value is up to2675m~2/g), matching well with thehigh-standard requirement of supercapacitor electrodes. The theoretical capacitance of graphene isup to550F/g and therefore has attracted much more attensions both in research and industry. Whenused in the form of powder, however, graphene shows its effective specific surface area of200-500m2/g that farly below2675m~2/g because of the intensive stacking amoung these two dimensionalsheets. To solve this problem, the three-dimensional (3D) graphene has become a hot research topicbecause this structure could sufficiently maintain the features of individual graphene and show alarge specific surface area. This thesis is focusing on the preparation of3D graphene by templatemethod and explore its electrochemical capacitance performce. The main contents are summarizedas follows:1. We put forward a route to synthesize3D graphene through chemical vapor deposition on thetemplate and substrate of aligned manganese dioxide (MnO2) nanowall that waselectrochemically deposited onto Ti substrate previously. We obtain different structure andproperties of3D manganese dioxide/graphene composite electrodes by controlling thetemperature of the CVD furnace. The so obtained manganese dioxide/graphene nanowallhybrids show good electrochemical capacitance performance. This provides a nove road toprepare the3D graphene and directs its potential applications.2. Graphene oxide prepared by Hummers is dissolved in the deionized water and put in ultrasonicfor half an hour and then take the template from above and finally by means of thin layerelectrodeposition growth of graphene on surface of the template. We obtain different structureand properties of3D manganese dioxide/graphene composite electrodes by controlling thereduction temperature of the furnace. The manganese dioxide/graphene nanowall hybrids arealso prepared and the electrochemical performance is good. This process is feasible and useful to develop another route to prepare3D graphene.