Dual-Compartment Electrocatalytic Oxidation of Polystyrene: Insights into Anode–Cathode Degradation Mechanisms and Differences

Microplastics (MPs) are toxic, persistent, and challenging to degrade, posing risks to ecosystems. While progress has been made in electrocatalytic degradation, most studies focus on optimizing electrode materials in single-compartment systems, with limited attention to anode–cathode degradation differences. This study investigated polystyrene (PS) degradation in a dual-compartment system using Peroxymonosulfate (PMS) catalysis at the anode and cathode, separately. After 3 h with 5 mM PMS, the cathode showed the highest weight loss rate of 39.5%, with 92.49% PMS consumed at 15 mA/cm2. In contrast, at the anode, the weight loss rate decreased from 26.50% to 15.3%, and PMS consumption increased from 42.71% to 95.25% as the pH rose at the same condition. Electron paramagnetic resonance and N2 pumping experiments revealed that the main radical at the anode was SO4•–, while at the cathode it was •OH, with the anode more reliant on O2. The PS particle size at both electrodes gradually reached around 50 μm, but the O/C ratio at the cathode was 1.95 times higher than that at the anode. At pH = 5, the cathode showed the highest total organic carbon (2540 μg/L), 2.58 times higher than that of the single-compartment system (984.3 μg/L). This study provides insights into electrode-specific degradation behavior, offering strategies for improving microplastic degradation and engineering applications.