Electrooxidation of polystyrene nanoplastics by modified Ti-felt electrodes

[EN] Ti-felt electrodes with high surface area have been used as supports of electroactive coatings (Pt and SnO₂–Sb–Pt). The electrodes obtained have been employed for the electrochemical oxidation of polystyrene nanoplastics (NPs) (100 nm) in solution. Voltammetric characterization of the electrodes with Ru(NH₃)₆Cl₃ and K₃Fe(CN)₆ redox mediators showed a substantial increase in the redox peaks' current density compared to the boron‑doped diamond electrode. For example, this increase was >68‑fold for the SnO₂–Sb–Pt electrode when using the Ru(NH₃)₆Cl₃ redox mediator. This can be attributed to the enhanced surface area of Ti‑felt, composed of 20 μm diameter fibers, and the roughness of the electrocatalyst coatings. Voltammetric characterization of Ti‑Pt and Ti‑SnO₂–Sb–Pt in 0.03 M Na₂SO₄ media showed an increase in the anodic current density when adding NPs, which would account for a direct mechanism of electrooxidation of the electrode. •OH, S₂O₈²⁻, H₂O₂, and O₃ generation were also determined for both types of electrodes. The degradation of NPs was monitored by fluorescence spectroscopy, taking advantage of the fluorescence of styrene. In addition, it was observed that the dispersion of the second‑order diffraction light (this phenomenon takes place in the diffraction grating of the monochromator) by NPs could also be used to monitor the evolution of the NPs concentration in solution. The electrochemical degradation of polystyrene NPs was faster with SnO₂–Sb–Pt modified Ti‑felt‑based electrodes than with the Pt‑modified one (reaching 90 % degradation in 100 and 210 minutes at 25 mA·cm⁻², respectively). Electrochemical energy consumption per order was also lower for SnO₂–Sb–Pt‑modified electrodes.