Graphene Prepared via the Dry Ice in Flames Method and Its Purification Using Different Routes: A Comparative Study

Although the dry ice method used to synthesize exfoliated graphite/graphene is little known and used, it has significant advantages over others: it is low cost, simple, and a large quantity of material can be obtained using some inorganic and highly available acids (which can be reused). Despite the above advantages, the main reason for its incipient development is the resulting presence of magnesium oxide in the final product. In the present work, three different treatments were tested to remove this remnant using some acid chemical leaching processes. Based on the experimental evidence, it was found that using aqua regia, among other chemical mixtures, was the most efficient way of removing such as remnant, the residue being only 0.9 wt.%. A mandatory high-energy mechanical milling stage was necessary during this treatment, in order to expose and dissolve the highly insoluble oxide without secondary chemical reactions on the graphenes. The obtained surface area was 504 m2g-1; this high value resulted from the intense exfoliation can potentiate the use of this material for a wide variety of applications.