Center for Intelligent Nano-Bio Materials, Department of Chemistry and Nano Sciences, Ewha Womans University, Seoul 120-750, Korea.
Chemistry. 2012 Feb 20;18(8):2263-71. doi: 10.1002/chem.201102646. Epub 2012 Jan 17.
Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40 mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100 m(2) g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167 F g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210 F g(-1) with good cyclability of around 95-97 % up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials.
通过简单地将剥离的还原氧化石墨烯（RGO）胶体加入到层状 MnO2 胶体中，合成了均匀混合的胶体悬浮液。当 RGO/MnO2 比值不超过 0.3 时，所得到的混合胶体悬浮液具有良好的胶体稳定性，没有任何相分离，且带有负电荷，ζ 电位为-30 至-40 mV。这些混合胶体悬浮液与锂离子的絮凝作用生成了具有高电化学活性和明显扩展表面积（约 70-100 m2 g-1）的多孔纳米复合材料 Li/RGO-层状 MnO2。与 Li/RGO 和 Li/层状 MnO2 纳米复合材料（≈116 和 ≈167 F g-1）相比，所获得的 Li/RGO-层状 MnO2 纳米复合材料的电容约为 210 F g-1，循环性能良好，在 1000 次循环中约为 95-97%，这表明杂化对 RGO 和锂锰氧化物电极性能的积极影响。此外，混合胶体悬浮液的电泳沉积使得容易地制造由石墨烯和氧化锰组成的均匀混合薄膜成为可能。所得到的薄膜表现出明显的电化学活性和 RGO 和 MnO2 的均匀分布。本实验结果清楚地表明，利用混合胶体悬浮液作为前体制备各种类型的石墨烯/金属氧化物混合材料提供了一种简单而通用的方法。
