Production of High-Quality Graphene Using a Novel Electrochemical Intercalation-Exfoliation Approach

Abstract

Large scale production of graphene has recently received a great deal of attention because of its interesting properties and wide range of potential applications. Conventional chemical exfoliation approaches, such as Hummer’s method,provides cost-effective pathway for large scale production, however, the method suffers from several key challenges such as the usage of corrosive and toxic solution, high processing temperature, long duration, and the poor quality of graphene produced which severely affects its potential applications. Recently, electrochemical exfoliation of graphene has been proposed for a high production yield with better quality. The electrochemical method involves two steps: 1) intercalation of ionic species between the graphene layers, followed by 2) oxidation of these ionic species under an anodic voltage into gas molecule enabling exfoliation of graphene flakes from the graphite electrode.1 In this study we examine a new approach to the intercalation, using an intercalating ion that has received very little attention and has not been evaluated for electrochemical exfoliation. The intercalation was followed by exfoliation in (NH4)2SO4 solution leading to the production of graphene flakes. The resultant graphene was found to have less disrupted sp2 lattice structure, with a high yield of about 95 % of graphene, along with high electrical conductivity and a low oxidation level (with a C:O ratio of about 15, determined by XPS). In addition, the presence of nitrogen and sulfur moieties in the resulting graphene structure can act as an electrocatalyst2 for applications such as the oxygen reduction reaction. Thus, the as-prepared graphene could be used for a range of electrochemical applications. References: (1) Sharif, F.; Zeraati, A. S.; Ganjeh-Anzabi, P.; Yasri, N.; Perez-Page, M.; Holmes, S. M.; Sundararaj, U.; Trifkovic, M.; Roberts, E. P. L. Synthesis of a High-Temperature Stable Electrochemically Exfoliated Graphene. Carbon 2019. (2) Singh, A.; Yasri, N.; Karan, K.; Roberts, E. P. L. Electrocatalytic Activity of Functionalized Carbon Paper Electrodes and Their Correlation to the Fermi Level Derived from Raman Spectra. ACS Appl. Energy Mater. 2019, acsaem.9b00180.