An innate quinone functionalized electrochemically exfoliated graphene/Fe<inf>3</inf>O<inf>4</inf> composite electrode for the continuous generation of reactive oxygen species

This study successfully demonstrated the controlled synthesis of innate quinone-functionalized graphene by an eco-friendly electrochemical exfoliation process. A quinone-functionalized electrochemically exfoliated graphene (QEEG) and QEEG/Fe3O4electrode was established for the continuous electro-generation of H2O2and[rad]OH radicals. The quality of the exfoliated graphene was assessed by Raman spectroscopy. The nature of functional groups and the oxidation states of QEEG and QEEG/Fe3O4composite were evaluated with X-ray photoelectron spectroscopy (XPS). High-resolution Transmission Electron Microscopic (HR-TEM) analysis shows that the Fe3O4nanoparticles (<10 nm) are uniformly dispersed on the surface of QEEG. The presence of a quinone functional group on QEEG domain and its role in oxygen reduction reaction for the formation of H2O2in acidic, neutral and alkaline conditions were examined. Significant enhancement in the production of H2O2was observed with QEEG electrode. Optimized QEEG/Fe3O4electrode achieved complete removal of Bisphenol A within 90 min at pH 3.0. Degradation efficiency of 98% was observed at neutral pH with less than 1% of iron leaching. Stable catalytic activity was observed even after 10 cycles of the experiments. On the basis of experimental results, the possible electro-Fenton oxidation mechanism with QEEG/Fe3O4composite cathode was proposed. Cleaner water treatment process was successfully demonstrated with no chemical addition and negligible iron contamination.