Oxidation-intercalation Process Research Of Large Diameter Graphite

Hummers,as a conventional method to produce graphene oxide,has advantages like simple process and realizable experimental conditions,which demonstrate great potential for mass-scale production.It includes two steps:oxidation-intercalation and exfoliation process,while oxidation-intercalation process is the key step.When the size of graphite is larger（over micron）,the mass transfer path of reactant among the graphite will be greatly extended.Difficulty of oxidation-intercalation process would be increased and the prime reaction conditions will cause incomplete oxidation-intercalation and exfoliation.In this work,graphites with sizes of 1400/710μm（14/25 mesh）were employed as the starting material.Specifically,we studied the influence of oxidant addition and the reaction time on yield and purity.By varying the amount of the oxidant,the velocity of oxidation-intercalation process was studied.Standing time was brought into the process for the sake of long mass transfer path,which decreased stirring resistance and time remarkably as well as energy consumption.Additionally,in comparison with KMnO₄,the influence of NaNO₃ on the Hummers reaction of graphite was limited.It was illustrated that for 14mesh graphite flakes,the optimal oxidation-intercalation condition obtained should be 2 g of graphite,1 g of NaNO₃,9.8 g of KMnO₄,70 ml of H₂SO₄;The reaction time for the first step is of 0.5 h,and the second step is of 2 h,finally,standed at room temperature for 48 h.Notably,an equimolar amount of NaNO₃ can be replaced by K₂SO₄,and a similar oxidation-intercalation result can be reached.The AFM（atomic force microscopy）imagings demonstrate that the probability of single atomic layered morphology of as-prepared graphene oxide sheets is high.By the introduction of standing time,mass transfer time can be prolonged,which promotes the full process of oxidation-intercalation and graphene oxide can be obtained with high yield.Consequently,the aforementioned results should be useful for further studies on graphite oxidation,and also the preparation of high quality of graphene oxide and chemically reduced graphene oxide.