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

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.