Dynamic Semiconductor Interface for Scalable Photoelectrochemical Synthesis of Chlorine Disinfectants from Natural Seawater

Abstract Photoelectrochemical seawater electrolysis for the chloride oxidation reaction (ClOR) suffers from low selectivity against competing reactions and high onset potentials, which severely limits its efficiency for disinfectant production and marine‐based chemical synthesis. Herein, we engineer an amorphous CoWO x layer on BiVO 4 photoanodes that enables highly selective active chlorine (AC) production directly from natural seawater. The CoWO x /BiVO 4 photoanode delivers a remarkable photocurrent density of 4.78 mA cm −2 at 1.2 V RHE under AM 1.5G illumination, with a record‐low onset potential of 0.38 V RHE . Notably, it maintains > 95% Faradaic efficiency and selectivity for AC production across a wide potential range of 0.9–1.8 V RHE , and retains 86.9% selectivity at 0.6 V RHE , overcoming the challenge of achieving efficient ClOR at low potentials. The incorporation of W suppresses the dissolution of Bi and V, while a dynamic Co 2+ /Co 3+ equilibrium ensures operational stability over 150 h. In situ characterization and density functional theory (DFT) calculations reveal that CoWO x accelerates Cl − oxidation to •Cl intermediates and steers the reaction pathways toward selective AC formation by thermodynamically favoring key chlorine adsorption configurations. Scaled‐up 25 cm 2 photoanodes achieves an AC production rate of 838 µmol h −1 . The resulting disinfectant exhibits broad‐spectrum bactericidal efficacy, including 99.99% inactivation of E. coli and S. aureus within 24 h. This work establishes a scalable photoelectrode design for the direct, energy‐efficient and selective production of valuable active chlorine from seawater.