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Raman Spectra of (a) MnO2-GO(1) and (b) MnO2-GO(2)sheets. (* α-MnO2)
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Figure 4: Raman Spectra of (a) MnO2-GO(1) and (b) MnO2-GO(2)sheets. (* α-MnO2)

Mentions: The typical Raman spectra taken from different regions of the samples are shown in Figure 4. They present one diagnostic Raman scattering band of α-MnO2, approximately 643 cm-1, which belongs to Ag spectroscopic species originating from breathing vibrations of MnO6 octahedra [30]. Two weak peaks recorded at approximately 305 and 360 cm-1 corresponding to the bending modes of O-Mn-O were observed in the spectra of the nanocomposites, stemming from the formation of Mn2O3 or Mn3O4 induced by the laser heating [31]. The appearance of a strong Ag-mode consists with our HRTEM result that the crystalline α-MnO2 has been readily formed on the GO support. Another two prominent peaks, D band (1,345 cm-1) and G band (1,597 cm-1), belong to GO [32-35]. From Figure 4, we can also see that the ratio of α-MnO2 to G is very different. MnO2-GO(1) has a larger α-MnO2 to G ratio than MnO2-GO(2), which means that the content of MnO2 in MnO2-GO(1) is higher than that in MnO2-GO(2). The Raman results are consistent with the inductively coupled plasma (ICP) and XPS results.

Influences of graphene oxide support on the electrochemical performances of graphene oxide-MnO2 nanocomposites

Yang H, Jiang J, Zhou W, Lai L, Xi L, Lam YM, Shen Z, Khezri B, Yu T - Nanoscale Res Lett (2011)

Bottom Line: MnO2 supported on graphene oxide (GO) made from different graphite materials has been synthesized and further investigated as electrode materials for supercapacitors.The surface area and functionalities of GO have significant effects on the morphology and electrochemical activity of MnO2, which lead to the fact that the loading amount of MnO2 on GO(1) is much higher than that on GO(2).As the electrode of supercapacitor, MnO2-GO(1) nanocomposites show larger capacitance (307.7 F g-1) and better electrochemical activity than MnO2-GO(2) possibly due to the high loading, good uniformity, and homogeneous distribution of MnO2 on GO(1) support.

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore, Singapore. yuting@ntu.edu.sg.

ABSTRACT
MnO2 supported on graphene oxide (GO) made from different graphite materials has been synthesized and further investigated as electrode materials for supercapacitors. The structure and morphology of MnO2-GO nanocomposites are characterized by X-ray diffraction, X-ray photoemission spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Nitrogen adsorption-desorption. As demonstrated, the GO fabricated from commercial expanded graphite (denoted as GO(1)) possesses more functional groups and larger interplane gap compared to the GO from commercial graphite powder (denoted as GO(2)). The surface area and functionalities of GO have significant effects on the morphology and electrochemical activity of MnO2, which lead to the fact that the loading amount of MnO2 on GO(1) is much higher than that on GO(2). Elemental analysis performed via inductively coupled plasma optical emission spectroscopy confirmed higher amounts of MnO2 loading on GO(1). As the electrode of supercapacitor, MnO2-GO(1) nanocomposites show larger capacitance (307.7 F g-1) and better electrochemical activity than MnO2-GO(2) possibly due to the high loading, good uniformity, and homogeneous distribution of MnO2 on GO(1) support.

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