Aims: To study the influence of the addition of graphene loading on the conductivity and stability of biopolymer composite solid electrolytes.
Study Design: Solution-casting technique using sol gel
method.
Place and Duration of Study: Chemistry Research Laboratory, Level
2, PASUM Complex, Centre for Foundation Studies in Science, Kuala Lumpur
between June 2016 until December 2018.
Methodology: These composites were synthesized by mixing of alpha
cellulose with graphene flakes via the solution-casting technique using sol gel
method. The addition of graphene into composite was varied between 10 wt.% to
70 wt.%.
Results: The X-ray diffraction (XRD) patterns revealed, at 60 wt.
% graphene loading, XRD patterns exhibited the decrease in intensity at peak
26° indicating that graphene is more dispersed in the alpha cellulose mixture
and reduced the crystallinity properties of biopolymer composite solid
electrolyte. Electrochemical impedance spectroscopy was used to determine the
conductivity of the composite. Sample without the addition of graphene acts as
an insulator with the lowest conductivity value of 1.77×10-7 S cm-1.
The highest conductivity achieved was 2.85×10-4 S cm-1
and observed at 60 wt.% graphene content. Fourier Transform InfraRed
spectroscopy showed the absorption peaks of C-O stretching vibrations of
composite was weakened and the hydroxyl group is slightly shifted compared to
the one without the addition of graphene. This might relate to dehydration of
cellulose. Thermogravimetric Analysis was used to study the thermal stability
and decomposition of composite. The derivative thermogravimetric curves, showed
two degradation peaks of composite. The first degradation peak (Tp1)
occurred between ~70 to 110˚C while the second degradation peak (Tp2)
was between 250-400˚C. Tp2 peak of composite with 60 wt.% and 70 wt.% were at
300 ˚C and 275˚C, respectively. This suggested that 60 wt.% graphene content
has higher thermal stability compared to 70 wt.%. Linear sweep voltammetry
results showed that the electrochemical stability of composite solid
electrolytes exhibited up to 3.2 V.
Conclusion: Biopolymer composite solid electrolyte with high
conductivity was successfully prepared using an eco-friendly method. BmimCl
ionic liquids are favorable in dissolving α-cellulose and aided graphene
dispersion. An increase in graphene content has increased the conductivity of
biopolymer composite provided that graphene is uniformly dispersed in a
cellulose matrix. This research provided an eco-friendly method to prepare cellulose/graphene
biopolymer composite which is useful in the energy field for future
applications.
Author (s) Details
Fauzani Md. Salleh
Chemistry Division, Centre for Foundation Studies in Science, University of
Malaya, 50603 Kuala Lumpur, Malaysia.
Farzana Abd. Hamid
Institute of Advanced Studies, University of Malaya, 50603, Kuala Lumpur,
Malaysia.
Nor Sabirin Mohamed
Physic Division, Centre for Foundation Studies in Science, University of
Malaya, 50603 Kuala Lumpur, Malaysia.
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