Bilayer electrified-membrane with pair-atom tin catalysts for near-complete conversion of low concentration nitrate to dinitrogen.

Discharge of wastewater containing nitrate (NO ₃ ^- ) disrupts aquatic ecosystems even at low concentrations. However, selective and rapid reduction of NO ₃ ^- at low concentration to dinitrogen (N ₂ ) is technically challenging. Here, we present an electrified membrane (EM) loaded with Sn pair-atom catalysts for highly efficient NO ₃ ^- reduction to N ₂ in a single-pass electrofiltration. The pair-atom design facilitates coupling of adsorbed N intermediates on adjacent Sn atoms to enhance N ₂ selectivity, which is challenging with conventional fully-isolated single-atom catalyst design. The EM ensures sufficient exposure of the catalysts and intensifies the catalyst interaction with NO ₃ ^- through mass transfer enhancement to provide more N intermediates for N ₂ coupling. We further develop a reduced titanium dioxide EM as the anode to generate free chlorines for fully oxidizing the residual ammonia (<1 mg-N L ^-1 ) to N ₂ . The sequential cathode-to-anode electrofiltration realizes near-complete removal of 10 mg-N L ^-1 NO ₃ ^- and ~100% N ₂ selectivity with a water resident time on the order of seconds. Our findings advance the single-atom catalyst design for NO ₃ ^- reduction and provide a practical solution for NO ₃ ^- contamination at low concentrations.
Competing Interests: Competing interests: The authors declare no competing interests.
(© 2025. The Author(s).)