SUPPORTING INFORMATION
Table S1. Zeta potential for each solution
Zeta Potential (mV)
1 st
2 nd
3 rd
Average
GO Suspension
-66.20
-63.33
-63.01
-64.18
GO/Ni(NO3)2 Solution
-5.72
-6.36
-4.13
-5.40
GO/Co(NO3)2 Solution
-6.68
-6.04
-4.77
-5.83
GO/Ni(NO3)2 and Co(NO3)2 Solution
-6.49
-5.33
-5.33
-5.71
Zeta potential for each solution is displayed in Table S1. The value of GO suspension is -64.18 mV, indicating
that GO is negative-charged heavily. When GO was mixed with metal ions solution, the positive-charged metal
ions would attached onto the GO sheets. Thus, the electronegativity of the GO decreased and the Zeta potential
increased to -5.40, -5.83, and -5.71 mV for GO/Ni(NO3)2, GO/Co(NO3)2, and GO/(Ni-Co)(NO3)2 solutions,
respectively. The change of Zeta potential confirmed the electrostatic attraction between GO and metal ions, which
is consistent with previous reports.[1]
Fig. S1 XRD patterns (a) and rate capacitance (b) of G-NCO with or without glucose.
Fig. S1a shows the XRD patterns of the two samples with or without addition of glucose, the peak at 42.7o
becomes stronger after adding the glucose in the system. The capacitance at different current densities is enhanced
with the addition of glucose. (Fig. S1b) What’s more, the stability of sample with glucose at 10 A g-1 is better than
that of the other one. It can be found that the glucose has a positive effect on enhancing the crystallinity and
cyclability of electrode materials.
Fig. S2 XRD patterns of G-CoO, GO and RGO.
Fig. S2 shows the XRD patterns of G-CoO, GO and RGO. The G-CoO was prepared via the same liquid phase
reaction with G-Co3O4, but annealed at 300 oC for 2h in Ar atmosphere, preventing the Co3O4 forming if annealed
in air. The peaks of G-CoO agree well with standard diffraction card of face-centered-cubic CoO (JCPDS card no.
43-1004) with a good crystallinity. For the GO sample, a diffraction peak at 11.16
o
is consistent with (001)
reflection, and after reduction, the characteristic peak of carbon from RGO could be found around 25.9 °.[2, 3] [4]
Table S2 XPS data of G-NiO, G-Co3O4, G-NCO, and GO
Bond
Peak BE (eV)
G-NiO
G-Co3O4
G-NCO
GO
C-C
284.6
50.41
54.79
52.44
42.17
C-O
286.2
27.79
28.58
30.48
36.79
C(O)O
288.1
20.79
16.62
17.07
21.04
Fig. S3 The fitted XPS spectra of Ni 2p and Co 2p for G-NiO, G-Co3O4, and G-NCO composites
As displayed in Fig. S3, the peaks of Ni 2p and Co 2p in all the three composites display a slight shift, which is
caused by the coexistence of Ni and Co. Two spin-orbit doublets at 856.6 and 874.6 eV can be identified as Ni
2p1/2 and Ni 2p3/2 signals of Ni2+, whereas the peaks indicated as “Sat” are assigned to Ni3+.[5, 6] Similar spin-orbit
doublets and shakeup satellites peaks at 782.2, 797.8 and 785.8, 803.7 eV are characteristic of Co2+ and Co3+.
[7]
The XPS results disclose that the NCO in G-NCO is a composition of Ni2+, Ni3+, Co2+, and Co3+. The Ni/Co ratio
of G-NCO is 2.3:1 according the XPS result, which is corresponding to the reactant ratio.
Fig. S4 TEM images of G-NiO (a), G-Co3O4 (b), and G-NCO (c)
Fig. S4a shows the wrinkle structure of RGO and no aggregation could be observed, but the NiO nanoparticle is
too small to be observed. In Fig. S4b and c, metal oxide nanoparticles cover all the surface of RGO without any
aggregation, meaning that the nanoparticles exhibit good dispersion. Thus, all the metal oxide particles exhibit
good dispersion on RGO.
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