Highly Controllable and Green Reduction of Graphene Oxide to Flexible Graphene Film with High Strength

Materials Research Bulletin, Volume 48, Issue 11, November 2013, Pages 4797–4803

Highly Controllable and Green Reduction of Graphene Oxide to Flexible Graphene Film with High Strength

Wubo Wan^a,Zongbin Zhao^a^,,Han Hu^a,Yury Gogotsi^a^,^b,Jieshan Qiu^a^,

^a Carbon Research Laboratory, Liaoning Key Lab for Energy Materials and Chemical Engineering, State Key Lab of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
^b Department of Materials Science and Engineering, and A.J. Drexel Nanotechnology Institute, Drexel University, Philadelphia, Pennsylvania 19104, USA

Highlights

•Graphene was synthesized by an effective and environmentally friendly approach.
•We introduced a facile X-ray diffraction analysis method to investigate the reduction process from graphene oxide to graphene.
•Flexible graphene films were prepared by self-assembly of the graphene sheets.
•The strength of the graphene films depends on the reduction degree of graphene.

Graphene film with high strength was fabricated by the assembly of graphene sheets derived from graphene oxide (GO) in an effective and environmentally friendly approach.

Highly controllable reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant, in which the reduction process was monitored by XRD analysis and UV-vis absorption spectra. Self-assembly of the as-made CCG sheets results in a flexible CCG film.

This method may open an avenue to the easy and scalable preparation of graphene film with high strength which has promising potentials in many fields where strong, flexible and electrically conductive films are highly demanded.



Highly controllable and green reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant. Self-assembly of the as-made CCG sheets results in a flexible CCG film, of which the tensile strength strongly depends on the deoxygenation degree of graphene sheets.


Fig. 4. (a) Stepwise reduction of GO to form CCG. (b) UV-vis absorption spectra of GO dispersed in water with different concentrations. The inset demonstrates the linear relationship between the maximum absorbance at the wavelength of 231 nm and the concentration of GO. (c) UV-vis spectra of GO dispersion change as a function of reaction time (from 0 to 18 h), the maximum absorbance of GO at 231 nm gradually red shifts to 268 nm.	Fig. 5. Photograph of the apparatus for measurement of I-V curves (a), and the I-V curves of the products obtained from different reaction times (b).

Fig. 6. (a) Digital photograph of a free-standing self-assembled graphene film, inset picture shows a strip of the film. (b) TEM image of CCG. (c) Cross sectional views of a self-assembled film, inset SEM image shows the side view of a CCG film at a higher magnification. (d) Optical transmittance of GO and CCG films. Inset shows photographs of GO (left) and CCG (right) films.	Fig. 7. (a) Tensile strength of CCG films prepared at different reaction times. (b) Digital photograph of a strip of graphene film supporting 275 g of load (the weight and the clamp), which is equal to 48 MPa of stress.