水热合成部分还原氧化石墨烯-K_2Mn_4O_8超级电容器纳米复合材料(英文)

Hydrothermal Synthesis of Partially Reduced Graphene Oxide-K_2 Mn_4 O_8 Nanocomposites as Supercapacitors

通过控制水热反应温度以及氧化石墨烯(GO)与高锰酸钾的填料比,合成了两组部分还原的GO-K2Mn4O8纳米复合材料.X射线衍射(XRD)分析说明水热过程中合成了α-MnO2和一种新的晶相K2Mn4O8.通过X射线光电子能谱(XPS)分析了水热反应前后氧化石墨的含氧官能团的变化.扫描电子显微镜(SEM)显示样品由片状还原的氧化石墨烯构成,其表面附有许多小的纳米颗粒,这种结构有利于储能时电子的传递.通过这两组复合材料的结构分析,更好地理解了材料的电化学性能的变化.利用循环伏安法和恒流充放电测试比较了材料的电容性能.用1mol·L-1的硫酸钠做电解液,电位范围是0-1V,在1A·g-1的电流密度下,测得的样品最佳比电容达到251F·g-1,能量密度为32Wh·kg-1,功率密度为18.2kW·kg-1.并且在5A·g-1的电流密度下循环1000次后样品的比电容仍维持在初始比电容的88%.

Nanocomposites of partially reduced graphene oxide （GO）-K2Mn,O8 were synthesized via a hydrothermal process at different temperatures and molar feed ratios of GO to KMnO,. X-ray diffraction （XRD） analysis confirmed that both mMnO2 and a novel crystal phase of K2Mn,O8 were obtained under the investigated hydrothermal conditions. X-ray photoelectron spectroscopy （XPS） revealed diverse changes of the oxygen-containing functional groups on the surface of GO depending on temperature and molar feed ratio. The microstructure of the composites was studied to help understand their electrochemical properties. A flaky structure of reduced graphene oxide （rGO） covered by nanoparticles was observed by scanning electron microscope （SEM）, which was considered to be favorable for charge transfer. The capacitive properties of the composites were compared using cyclic voltammograms and galvanostatic charge-discharge measurements. The specific capacitance of the optimal sample was calculated to be 251 F· g^-1 with an energy density of 32 Wh· g^-1 and a power density of 18.2 kW· g^-1 in 1 mol· L^-1 Na2SO4 electrolyte at a current density of 1 A· g^-1 between 0 and 1 V. Moreover, the capacitance retention ratio of this sample remained at 88% after 1000 cycles at a high current density of 5 A· g^-1.