Mg anode-assisted photocatalytic fuel cell system for antibiotic/ nitrogen/ phosphorus removal and simultaneous electricity generation in seawater

The coexistence of antibiotic and nitrogen/ phosphorus nutrient pollutants in mariculture wastewater presents a considerable challenge for their simultaneous remediation. In this study, a novel photocatalytic-Mg metal-coupled fuel cell (PMFC) system based on Mg anode and Co/MoS 2 /CC photocathode was developed to achieve dual-circuit energy conversion and antibiotic and nitrogen/ phosphorus simultaneous removal. Under simulated marine conditions, the PMFC system achieved 93.34% removal of norfloxacin (NOR), which was higher than that of the photocatalytic fuel cell (PFC) system (67.66%). Meanwhile, almost all PO 4 3− and 43.28% NH 4 + were removed via struvite precipitation and direct ammonia oxidation, while delivering a maximum power density of 7.62 mW/cm 2 . Mechanistic investigations, combining density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurements, revealed that exogenous electrons from the Mg anode enhance the separation and transport efficiency of photogenerated carriers. Co sites of the cathode served as electron accumulation centers, concurrently capturing photogenerated and exogenous electrons. A synergistic effect between the exogenous electron and the regulation of the cathode's electronic structure by Co-modification enhanced power generation, while reducing the oxygen reduction overpotential of the cathode. Radical quenching experiments demonstrated that Cl − was effectively activated through chain reaction, leading to the dominant active species controlling NOR degradation shift from •OH and • O 2 − to ClO• and • O 2 − . This study integrated pollution control, electricity generation, and resource circulation in mariculture wastewater, providing an efficient solution for the sustainable development of industry.