|A next step in graphene mass-production has been reported by Parvez et al. in JACS (DOI). Experimental electrochemical set-up: one graphite flake as working electrode and one platinum bar as reference electrode in a solution of ammonium sulfate and with a 10 volt direct current. Within minutes the graphite has exfoliated and dispersed up to a 75% yield. Filtration and washing do the rest. Product: graphene, in a 16 gram batch. Makes the Scotch tape method seem as awkward as a flint in fire-making. |
Rationale according to the authors: reduction of water produces hydroxyl anions that eat away at the graphite edges, the graphene layers expand and sulfate ions can intercalate between the layers. In stage three oxygen gas and sulfur dioxide gas also formed in the electrolysis process agitate the layers even further and the whole thing comes apart. Dimensions: width between 5 and 44 micron, thickness on average 0.7 nanometers.
The material was field-tested in a supercapacitor set-up: graphene was dissolved in DMF and coated onto regular A4 paper. The resulting conductive sheet was coated with a poly(vinyl alcohol)/ sulfuric acid gel and after solidification two put together formed a working capacitor.