Effects of reduction method on reduced graphene oxide and its electrochemical energy storage performance

Abstract

To enhance the application of reduced graphene oxide (rGO) in energy storage field, the effects of reduction method on rGO and its electrochemical energy storage performance were researched in this paper. Green and environmentally friendly reduction methods, such as l-ascorbic acid method (LAA), hydrothermal method and sodium borohydride method (NaBH4), were used to reduce the GO obtained by Hummers' method to rGO. The obtained samples were analyzed and characterized by Fourier transform Infrared spectroscopy, Ultraviolet-visible spectroscopy, X-ray diffraction, scanning electron microscope, Raman spectroscopy and N2 absorption and desorption. The obtained rGO samples were being assembled into symmetrical electrochemical super-capacitors with using organic solution as the electrolyte to characterize their electrochemical energy storage performance including cyclic voltammetry, galvanostatic charge and discharge, AC impedance and cycle life tests. The research results showed that the GO could all be changed into rGO via the reduction methods mentioned above, but the reduction degree and morphology structure of the obtained rGOs were quite different: the rGO obtained by LAA had a very smooth surface; the surface of rGO obtained by hydrothermal reduction method had wrinkles and formed a layered cross-linked structure; while the rGO obtained by NaBH4 showed severe agglomeration, forming obvious blocks. The electrochemical test results showed that the rGO obtained by hydrothermal reduction had the best electrochemical performance among the samples: its specific capacitance could reach 140 F g−1 (organic electrolyte) at a current density of 1 A g−1, moreover it had an energy density of 43.75 Wh kg−1 and a power density of 4500 W kg−1.