Mixed Colloidal Suspensions of Reduced Graphene Oxide and Layered Metal Oxide Nanosheets: Useful Precursors for the Porous Nanocomposites and Hybrid Films of Graphene/Metal Oxide

Abstract

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.

Synthesis and enhanced electrochemical supercapacitive properties of manganese oxide nanoflake electrodes

“…This suggests that the film's crystallinity improves with increasing oxygen partial pressure. These results are associated with the formation of a layered structure of manganese oxide nanoflakes with a birnessite phase [14,29].…”

Electrophoretic deposition of graphene-related materials: A review of the fundamentals

“…carbon black [15], CNTs [151,164], partiallyunzipped carbon fibres [63], ZnS [155], CoFe 2 O 4 [119], Ni [96,120]) as inter-layer spacers between deposited GRM sheets. Lee et al [165] reported that EPD using mixed suspensions of rGO and layered metal oxide nanosheets led to formation of porous morphologies via a house-of-cards-type stacking. In general, the additional nanoparticles in GRM films also increases the films' surface roughness [15,50], since…”

Exfoliation-restacking synthesis of coal-layered double hydroxide nanosheets/reduced graphene oxide composite for high performance supercapacitors

“…Corresponding pore size distribution reveals that the GL7 and CAN-LDH are belong to mesoporous materials with an average diameter of 3.8 nm and 17.6 nm, respectively. These mesoporous configuration can be ascribed to the porous structure of two-dimensional stacking nanosheets crystallites [44]. The reduced mesopores size can be attributed to the addition of rGO, which resulted in the smaller interlayer space than the CAN-LDH.…”