Highly active and stable ferrocene functionalized graphene encapsulated carbon felt array - A novel rotating disc electrode for electro-Fenton oxidation of pharmaceutical compounds

In this study, ferrocene functionalized electrochemically reduced graphene oxide (Fc-ErGO) was used as electro-Fenton catalyst in rotating disc electrode system for the continuous generation of reactive oxygen species without external aeration. The nature of Fc-ErGO was evaluated using X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis. Degradation of ciprofloxacin and carbamazepine were carried out to evaluate the performance of reactor. Enhanced removal rate was achieved at a wider range of pH as compared to the unmodified and ErGO modified graphite felt electrode systems. An increase in rotational speed of the disc electrodes resulted in enhanced removal rate due to improved mass transfer activity. At neutral condition, the removal rate was found to be 0.199 min⁻¹ and 0.082 min⁻¹ for ciprofloxacin and carbamazepine, respectively. Quantification of reactive oxygen species was also done. The Fc-ErGO modified cathode showed 644 μM, 264 μM, and 163 μM of • OH radicals at pH 3.0, 7.0 and 9.0 respectively; it confirms that ferrocene efficiently catalyses the conversion of H₂O₂ to • OH radicals and facilitates the degradation of contaminants. Stable catalytic activity was achieved even upto 10 cycles of repeatable experimental runs. A highly efficient, cleaner electro-Fenton system without external aeration and chemical addition was successfully demonstrated.