Non-destructive, uniform, and scalable electrochemical functionalization and exfoliation of graphite

Exfoliation of graphite through functionalization is a promising technique to produce two-dimensional (2D) nanocarbons on a large scale. Due to the high stability of graphite, a conventional functionalization of graphite has been performed in harsh conditions, such as in concentrated sulfuric acid. Therefore, environmental and safety have been problems for scaling up the operation. In contrast, the electrochemical functionalization of a graphite electrode has recently attracted considerable attention because it does not require oxidants or sulfuric acid. However, 2D carbons produced through the existing electrochemical method are generally lacking in quality, due to the non-uniform destruction of the intermediately functionalized graphite. This paper reports a method for the non-destructive functionalization of graphite using HBF₄ diluted by water or methanol as an electrolyte. It is confirmed that the choice of solvents and electrochemical conditions enabled fine control over the functionalization degree and the type of functional groups on 2D carbons. Compared to chemically generated 2D carbons, the electrochemically generated 2D carbon exhibits similar or better physical and chemical properties when used in lithium-ion battery electrodes and water purification membranes. This electrochemical method is also applicable to a continuous flow system, thus promising the mass production of 2D carbons for future industrialization.