Properties of graphene/nano diamond composite electrode
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摘要: 为开发具有高能量密度、高功率密度和长寿命的超级电容器复合电极,将纳米金刚石(nano diamond,ND)经真空热处理获得石墨化纳米金刚石(graphitized nano diamond,GND),再采用超声法将不同质量比的石墨烯与GND制备成复合电极,进行电化学性能测试并分析其结构。电化学性能测试结果表明:质量比为4∶1时制备的石墨烯/GND复合电极具有良好的双层电容特性,其循环伏安曲线近似呈矩形且形状几乎不随扫描速率变化而改变。在扫描速率为2 mV/s,电解液为0.5 mol/L的K2SO4溶液的条件下,其比电容高达103.3 F/g;经循环扫描1000圈后,比电容衰减幅度不到0.95%,具有优异的循环稳定性。经透射电镜分析可知:真空高温处理后ND表面形成石墨烯层;受金刚石结构的制约,石墨烯层间距由内向外逐渐增加,提高了复合电极的导电性。由扫描电镜形貌表征可知:GND均匀附着在石墨烯表面,在石墨烯的片层之间形成阻断,防止石墨烯的杂乱堆叠,有利于电解液的扩散,从而使复合材料的比电容增大、电化学性能提高。Abstract: Composite electrode of graphitized nano diamond (GND) and graphene was prepared to satisfy the requirements of super capacitor on higher energy density, higher power density and longer service life. GND was prepared by vacuum heat treating nano diamond (ND). Graphene/GND composite electrodes with different mass ratios were prepared by ultrasonic mixing method. The electrochemical performance of the electrodes was tested and their structures were analyzed. Resluts show that when the mass ratio is 4∶1, the prepared grahpene/GND composite electrode exhibited a good characteristic of double layer capacitor, whose voltammetric curve is almost rectangular and the shape remains nearly stable as scanning speed changes. When the scanning speed is 2 mV/s and the solution is 0.5 mol/L K2SO4, the electrode has a high specific capacitance of 103.3 F/g which decays no more than 0.95% after 1000 scanning cycles, showing excellent cycling stability. TEM result indicates that graphene layers are formed on the surface of nano diamonds after heat treatment and that the surface of graphene is restricted by the diamond structure. The graphene layer spacing gradually increases from the inside to the outside and improves the conductivity of the electrode. The SEM analysis concludes that GND is uniformly adhered to the surface of the graphene, forming blocks between graphene sheets and preventing messy graphene stack, which is good for the diffusion of electrolyte and increases the specific capacitance of composite material and its electrochemical performance.
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Key words:
- graphene /
- nano diamond /
- composite electrode
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