XPS analysis of the carbon rod anodes and cathodes has been performed to determine the impact of DESs of Types I and IV on the exfoliation process. Fig. 6 shows the XPS data for the graphite rod after it has been intercalated only by the IL (anode) or by the DES (cathode). The powdered residue collected after exfoliation was also subjected to XPS analysis. The results clearly show that zinc cations intercalate into the cathode while a small amount of fluoride anions intercalate into the anode, particularly when IL is used. The intercalation of these HA14-1 into the carbon electrodes are directly responsible for the enhanced graphene yield obtained when using DESs of Types 1 and IV. While these ions are absent from the IL, both DESs contain them, although to a lesser degree in the case of Type I DESs as discussed in the following paragraph.
Fig. 6. XPS images of exfoliated graphene products and electrodes after exfoliation in either Type I or Type IV DES with or without IL. Acetonitrile is radially symmetrical the solvent in all cases. (a) Graphite rod; (b) positive graphite electrode after exfoliation of graphene with IL and Type IV DES; (c) positive graphite electrode after exfoliation of graphene with Type I and Type IV DES (without IL); (d) negative graphite electrode after exfoliation of graphene with IL and Type I or Type IV DES; (e) negative graphite electrode after exfoliation of graphene using Type I or Type IV DES (without IL); (f) graphene powder after exfoliation in IL and Type I or Type IV DES.Figure optionsDownload full-size imageDownload as PowerPoint slide