氢氧化镍纳米线/三维石墨烯复合材料的制备及其电化学性能

Preparation and Electrochemical Performance of Ni(OH)_2Nanowires/Three-Dimensional Graphene Composite Materials

采用水热法制备了氢氧化镍纳米线/三维石墨烯复合材料及作为比较的三维石墨烯、氢氧化镍纳米线、还原氧化石墨烯和氢氧化镍纳米线/还原氧化石墨烯,通过X射线衍射、扫描电镜、热失重分析和氮气吸脱附表征了材料的形貌、结构和组成,并采用循环伏安法和恒电流充放电测试了复合材料的电化学性能.结果表明:氢氧化镍纳米线/三维石墨烯复合材料中直径为20-30 nm的氢氧化镍纳米线和三维结构的石墨烯紧密结合,相互交联形成网状结构,其比表面积达到136 m2·g-1,孔径分布20-50 nm,氢氧化镍纳米线的含量达到88%(w,质量分数).在6 mol·L-1的KOH电解液中,复合材料的比电容在1 A·g-1电流密度下达到1664 F·g-1,在1 A·g-1电流密度下循环3000次后的比电容保持率为93%.将复合材料的比电容和循环性能与氢氧化镍纳米线、氢氧化镍纳米线/还原氧化石墨烯、三维石墨烯和还原氧化石墨烯的性能进行比较,发现三维石墨烯较还原氧化石墨烯具有更高的比表面积和三维多孔结构,可以更大地提高活性物质的利用率,进而提高复合材料的比电容和稳定性.

We synthesized Ni（OH）2 nanowires/three-dimensional graphene composites using a hydrothermal method, and compared their properties with those of three-dimensional graphene, Ni（OH）2 nanowires, reduced graphene oxide, and Ni（OH）2 nanowires/reduced graphene oxide. The samples were characterized using X- ray diffraction, scanning electron microscopy, thermogravimetric analysis, and N2 physisorption measurements. The electrochemical performances were investigated using cyclic voltammetry and galvanostatic charge- discharge methods. The results showed that Ni（OH）2 nanowires of width 20-30 nm were closely combined with graphene and crosslinked to one another to form a three-dimensional structure with a high specific surface area （136 m2·g^-1） and mesoporosity （pore diameter 20-50 nm）. The mass fraction of Ni（OH）2 nanowires in the Ni（OH）2 nanowires/three-dimensional graphene composite was 88%. The maximum specific capacitance of the Ni（OH）2 nanowires/three-dimensional graphene composite was 1664 F· g^-1 in 6 mol· L^-1 KOH electrolyte at 1 A· g^-1. The specific capacitance decreased by only 7% after 3000 cycles at 1 A· g^-1. A comparative study of the specific capacitances and cycling performances of Ni（OH）2 nanowires, Ni（OH）2 nanowires/reduced graphene oxide, three-dimensional graphene, reduced graphene oxide, and Ni（OH）2 nanowires/three-dimensional graphene indicated that three-dimensional graphene with three-dimensional porosity and a larger specific surface area than conventional reduced graphene oxide enabled improved use of the active material and significantly enhanced the electrochemical performance of Ni（OH）2 nanowires.