Double-spiral TiO2 nanoflower fiber electrodes enable coating-free electrocatalytic membrane ozonation through field-driven interfacial •OH oxidation.

Electrocatalytic membrane ozonation (EMCO) improves O3-to-•OH conversion at the membrane-liquid interface, but prevailing designs deposit conductive or catalytic coatings on hydrophobic membranes, risking pore blockage, altered hydrophobicity, and coating detachment. Whether the O3-activation region near a membrane can be electrified without making the membrane conductive remains unresolved. Here, a double-spiral EMCO module was assembled by alternately winding a TiO2 nanoflower-modified Ti fiber anode (TiO2-NF/Ti) and a graphite-coated Ti cathode around an unmodified polytetrafluoroethylene (PTFE) hollow-fiber membrane, generating a continuous band-like electric field along the membrane-side reaction zone while retaining bubble-free O3 delivery through the membrane lumen. For p-chlorobenzoic acid (p-CBA) degradation, EMCO(TiO2-NF/Ti) gave an apparent first-order rate constant of 9.7 × 10⁻3 min⁻1, 1.67-fold that of the electrified bare-Ti control and 1.76-fold that of the unelectrified TiO2-NF/Ti control, together with the lowest O3 exposure (8.5 × 10⁻3 M·s) and the highest Rct (8.37 × 10⁻9) among five configurations. Kintecus modeling estimated that surface-bound •OH accounted for more than 99% of the modeled total •OH concentration, while in situ confocal imaging showed interfacial fluorescence enrichment. These results support interfacial O3-to-•OH conversion in a configuration using an unmodified PTFE membrane, with the membrane mainly serving as the O3-transfer pathway.