Green preparation of reduced graphene oxide using a natural reducing agent

A simple and efficient method was introduced for the high-conversion preparation of graphene oxide (GO) from large graphite flakes (average flake size=100 μm) using a simplified Hummer׳s method. Natural reducing agents such as lemon juice and vinegar were compared with hydrazine (N2H4) as potential reducing agents. Graphene was prepared by chemical reduction of GO because this method was low cost and could be used for large-scale graphene production. This one-pot graphene preparation was performed at room temperature. Different degrees of oxidation of graphite flakes were obtained by stirring graphite in a mixture of sulfuric acid and potassium permanganate at different oxidation times, and highly exfoliated GO sheets were produced. GO was subsequently reduced effectively by lemon juice, a new, green, and potential reducing agent with pH 2.3. This reduced GO exhibited a high electrical conductance of 24.6 μS attributed to its higher C/O ratio (≈8:2) compared with other samples.