Controlled Reduction of Graphene Oxide (GO) Film Using Low-Density Glow Discharge Hydrogen Plasma

In the present work, reduced graphene oxide (rGO) is produced through hydrogen plasma treatment of chemically prepared graphene oxide (GO) film. The SEM top surface images show the wrinkled and layered flake structures for GO whereas a more etched surface with thinner sheets and a wrinkled, paper-like structure for rGO. From cross-sectional images of the GO and rGO films, it is found that the film thickness is reduced prominently after plasma treatment. The EDX analysis of GO and rGO confirms the successful reduction of graphene sheets. The XRD pattern shows a wide diffraction peak at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\theta = 11.21^{\circ }$ </tex-math></inline-formula> corresponding to an interlayer spacing of 7.9Å and lattice plane (001) for GO. In contrast, the peak is prominently decreased and shifted to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\theta = 11.82^{\circ }$ </tex-math></inline-formula> corresponding to an interlayer spacing of 7.5Å after the plasma treatment. The atomic force microscopy (AFM) analysis shows that the increase in surface roughness of rGO in comparison with untreated GO. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy analysis confirm the reduction of different oxygen functionalities for rGO in comparison with pristine GO. The Raman spectrum of GO displays two prominent peaks designated as the D band at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx\! 1353.07$ </tex-math></inline-formula> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and the G band at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx\! 1586.82$ </tex-math></inline-formula> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, whereas, for rGO, the peaks for D and G bands are observed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx\! 1354.88$ </tex-math></inline-formula> and 1593.96 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>, respectively. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{D}$ </tex-math></inline-formula>/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{G}$ </tex-math></inline-formula> ratio increased for rGO (~9%) after the hydrogen plasma treatment implies that a limited amount of damage has occurred which causes the relative disorder. There is also a prominent improvement in the electrical properties of the rGO as compared with GO, which suggests that the plasma reduction approach is a very efficient technique for rGO preparation with higher conductivity.