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It was demonstrated that the galvanostatic polarization of graphite electrodes in a cell with two separated compartments generates simultaneously and straightforwardly, without further separation and functionalization, two distinct sets of hydrophilic carbon nanomaterials [electrogenerated hydrophilic carbon (EHC)], in the anodic and cathodic compartments, respectively. The synthesized products comprise an amorphous carbonaceous material with aromatic sp2 carbon clusters, differing mainly in their oxidation degree. Surprisingly, it was found that nitrogen is incorporated in the carbon‐based material during the electrolysis, which is provided by the N2 gas present in the air and/or aqueous medium. This phenomenon is explained on the basis that very reactive carbonaceous species are formed during the electrodes polarization, owing to an anomalous high electric field generated along the galvanostatic polarization. In addition, it was also evidenced that ECH materials display a negative charge, counterbalanced by sodium ions and unique optical properties, exhibiting deep ultraviolet emission (ca. 4.1 eV), as well as blue luminescence. It is foreseen that these carbon materials will have important repercussions in optoelectronics devices, energy technology (supercapacitors, batteries, and fuel cells), and biomedicine.

Here we show that the main product released from graphite in the early stages of the anodic polarization is a carbon-based salt comprised of an amorphous carbonaceous material with delocalized negative charge, counterbalanced by sodium cations. Remarkably, this material shows a dual behaviour: it behaves as an electrolyte in aqueous medium, which has the ability to enhance the capacitive properties of the electrodesolution interface and in the solid state it can be used as an electrode material with meaningful capacitive properties.Although the electrochemical approach is one of the most successful synthetic methods for the top-down preparation of a wide spectrum of graphene particles with variable sizes and shapes, like sheets, [1][2][3][4][5] nanoribbons, [6] flakes [6][7][8] and quantum dots, [9][10][11] the nature of the species formed upon the electrochemical oxidation of graphite is still an unclear matter. A close reading of the literature reveals that there is no clear specification of the electrochemical conditions required to prepare selectively just one type of graphene-based material. Notwithstanding, it is known that the chemical composition of the electrolyte and water content of the medium have a crucial effect on the size of the carbon nanoparticles. [6,12,13] It is thus expected that a mixture of different graphene-based structures may be inevitably formed when the electrochemical synthesis is performed in aqueous medium, which explains the common lab practice of centrifugation and filtration after the electrochemical essays. Even though these operations are decisive to improve the selectivity of the production process, they inevitably mask the nature of the species formed. In order to overcome this constrain, the present work was initially motivated to clarify what type of carbon materials are released elec-trochemically from a graphite anode in the early stages of the electrode polarization. No separation process other than dialysis (to remove the electrolyte) was used. More importantly, this study lead us to the finding that the main type of carbon material generated at the anode shows unprecedent electrochemical properties when dissolved in aqueous medium: ability to behave as an electrolyte and to enhance the capacitive properties of the electrode-solution interface.The electrochemical oxidation of graphite was performed under experimental conditions adapted from the literature. [10,11] It was used a phosphate buffer solution (pH 7) and graphite rods as the anode and cathode electrodes. The anodic polarization was carried out under galvanostatic control. The solution removed from the anode compartment after one hour of electrode polarization was transparent and colourless and no visible signs of graphite expansion on the anode was observed. However, analysis of this solution by a Total Organic Carbon analyser (TOC) revealed a significant amount of carbon released from graphite during the galvanostatic polarization (typically 7-10 mg/L). Before further characterization, the anodic solution wa...