Respiratory burst-inspired triphase interfacial synergy for sustained cathodic oxygen activation in water purification.

Cathodic oxygen activation (COA), exemplified by electro-Fenton process, offers an attractive route for water purification. Yet at triphase cathodic interfaces, limited O2 availability restricts reactivity, whereas static cathodic polarization causes charge accumulation and pH drift that compromise durability. Here, inspired by the neutrophil respiratory burst, we developed a burst-recovery triphase interface (BRTI) that mimicked rapid O2 uptake and compensatory regulation of the cathodic microenvironment to sustain oxygen activation. In a flow-through configuration, anodically evolved O2 was convectively delivered to a downstream FeS2@OH-DHTA cathode, where oscillatory polarization alternated the interface between activation and recovery. During activation, hydrogen-bonding domains rapidly captured and enriched O2 near Fe-S motifs, enabling a thermodynamically favorable and kinetically coupled three-electron O2-to-•OH cascade. During recovery, relaxation pulses dissipated accumulated interfacial charge, removed OH⁻ and restored proton availability, thereby maintaining O2 affinity and Fe redox cycling while mitigating drift-induced passivation. This activation-recovery cycle sustained •OH generation during 2,4-dichlorination degradation and achieved 94.4 ± 2.8% utilization of anodically evolved O2 without external aeration. The system further enabled 100 h single-pass treatment of real coal-chemical wastewater, achieving COD removal at 25.5 g m⁻2 h⁻1 with energy consumption of 0.086 kWh g⁻1 COD. Techno-economic analysis estimated normalized treatment costs 97.1 ± 2.2% below those of conventional advanced oxidation processes. This study offered a functionally bioinspired paradigm for triphase COA interface design toward efficient, economic and sustainable electrochemical water purification.