3D Macroporous Nitrogen-doped Graphene Frameworks for High-Performance Supercapacitors
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3D Macroporous Nitrogen-doped Graphene Frameworks for High-Performance Supercapacitors Pingping Yu, Xin Zhao, Yingzhi Li and Qinghua Zhang State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, People’s Republic of China ABSTRACT A novel type of nitrogen-doped hierarchically 3D macroporous CMG films electrode (NCMG) was prepared through a facile ultrafiltration method using graphene oxide (GO) and polystyrene (PS) as precursors, then annealed in N2 atmosphere at 1000°. This NCMG electrode exhibits high specific capacitance (150 F g-1), excellent rate capacity and good cycle life (98% of initial capacitance), which can be a good candidate for supercapacitor application. INTRODUCTION High energy and power densities energy storage devices are urgently demanded to meet challenges of the fast development of large-scale electric energy storage such as cordless electric tools, hybrid electric vehicles and industrial energy management [1]. The development of supercapacitors has focused on the use of graphene, due to its excellent electric and mechanical properties, chemical stability, high specific surface area up to 2675 m2 g-1, and feasibility for large-scale production (especially the chemically modified graphene CMG) [2-3]. Most of works on graphene-based nanocomposites have been achieved by incorporating guest nanoparticles onto 2D graphene sheets [4]. However, those structures suffer from graphene aggregation, which causes inferior ionic accessibility and thus modest improvement in the cell performance. The randomly and loosely stacked graphene sheets have large interface resistance, which would make it difficult for ions to gain access to the electrode surfaces. In our paper, we fabricate a novel type of N-doped hierarchically 3D macroporous CMG films electrode (NCMG) through a facile ultrafiltration method using graphene oxide (GO) and polystyrene (PS) as precursors. After calcinations in N2 atmosphere at 1000°, the as-prepared GO/PS composites become interconnected macroporous NCMG film. The NCMG film holds novel hierarchically porous architectures, which could intrinsically optimize ion transport and also provide sufficient contact area between the electrode and electrolyte. The resultant 3D macroporous NCMG film shows high specific capacitance (150 F g-1), excellent rate capability, and long cycle life (98% of the initial capacitance), NCMG is an attractive scaffold candidate for conducting polymers and metal oxides. EXPERIMENT Graphene oxide sheets (GO) were initially prepared by the modified Hummers method and then dispersed in water (0.05 wt %) by a sonication process at pH=6. The PS solution was
prepared by dispersing PS particles (10 wt %, 2μm mean particle size, Aldrich) in deionized water at pH= 6. Two components were oppositely charged (GO: negative, PS: positive), leading to uniform distribution of PS particles in the GO films. The PS/GO films were produced by filtering the mixed solution by vacu
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